ORCID Profile
0000-0002-7604-7097
Current Organisations
University of Oxford
,
University of Melbourne
,
Centre for Eye Research Australia Ltd
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Publisher: Wiley
Date: 06-2001
DOI: 10.1046/J.1442-9071.2001.00400.X
Abstract: Topical steroidal anti-inflammatory drugs (SAID) and non-steroidal anti-inflammatory drugs (NSAID) are known to affect fluid balance. The effects of twice daily topical applications of Maxidex (dexamethasone, a SAID), Acular (ketorolac, a NSAID), and saline were examined biometrically on the development of refractive errors and eye growth in chicks raised from days 3-12 wearing either a monocular +10 D, 0 D, or -10 D lens. Biometric analysis showed that neither SAID nor NSAID nor saline affected refractive error compensation but that the anti-inflammatory drugs affected eye growth. In chicks reared with a +10 D lens, dexamethasone induced a decrease in axial length (AL), vitreous chamber (VC) and anterior chamber (AC) depth, while ketorolac only induced a decrease in AC. In -10 D lens chicks dexamethasone again induced a decrease in AL and VC, but did not affect AC depth, whereas ketorolac only induced an increase in AC depth. Taken together, these results suggest that anti-inflammatory drugs can induce changes in ocular size without affecting refractive state and, as such, have implications for the management of progressive myopia.
Publisher: Informa UK Limited
Date: 05-2004
DOI: 10.1111/J.1444-0938.2004.TB03169.X
Abstract: Measures of visual function thresholds such as visual acuity and visual fields are generally dependent on subjective responses and assume maintenance of fixation, attention and motivation. In the young, elderly, cognitively impaired or malingering populations, such measures may be inaccurate or difficult to obtain. The Visual Evoked Response Imaging System (VERIS) has been claimed to give more objective topographic recordings of retinal and cortical function. This paper aims to explore the adequacy of this technique in four unusual, unrelated, clinically difficult cases. Multifocal visual evoked potentials (mfVEPs) recorded on the VERIS System 3.01 are used to assess visual function in four cases with contradictory clinical findings or unreliable subjective responses. Patient 1 had sustained a head injury and had normal ocular and pupil examination but light perception in the right eye and 6/5 acuity in the left. Multifocal VEPs showed a marked depression of the right visual field with little macular response. Patient 2 had sustained a head injury, had a left field hemianopia, possible macular sparing and loss of much of the right field, reduced but variable visual acuities, good near vision and normal ocular fundi. Multifocal VEPs showed a severe depression in both visual fields (L more than R) with little macular response. Patient 3 had a left optic nerve meningioma and experienced great difficulty with visual field assessment. mfVEPs showed a bilateral depression in the superior field particularly the left field, with a larger deficit in the left eye. Patient 4 had unexplained visual acuity and peripheral field deficits. mfVEP results were inconclusive in this case. Where there is difficulty performing traditional techniques or conflicting clinical findings, mfVEPs may provide additional objective information to aid in the assessment of patients.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 18-10-2016
Abstract: We determine the feasibility of using a dark-adapted chromatic (DAC) perimeter to obtain dark-adapted static and dynamic rod function at multiple retinal locations, and compare these functional parameters between subjects with intermediate age-related macular degeneration (AMD) and normal controls. Perimetric dark-adapted retinal sensitivities for the 505 and 620 nm stimuli across 7 retinal locations within the central 12° were repeatedly measured after exposing to a single photobleach in 22 intermediate AMD subjects and 8 controls. The sensitivities for each stimulus at 20 minutes after bleach and the sensitivity difference between the stimuli were used to determine static rod function. Sensitivities for the 505 nm stimulus at various times within the initial 20 minutes after bleach were used to estimate the rod criterion time to determine rod function dynamics. The static and dynamic rod functional parameters were compared between AMD and control eyes. Compared to the control eyes, AMD eyes had a reduction in retinal sensitivities for the 505 nm (P < 0.001) and 620 nm (P < 0.001) stimuli, a reduction in sensitivity difference (P < 0.001), and an increased in rod criterion time (P < 0.001). Region within the central 6° appeared to be the most defective and AMD eyes with reticular pseudodrusen (RPD) seemed to have worse function than eyes without RPD. It is feasible to use a DAC perimeter to study dark-adapted static and dynamic rod-mediated function at multiple retinal loci. Static and dynamic rod function were abnormal in intermediate AMD and more so in eyes with RPD, particularly within the central 6° retina.
Publisher: Frontiers Media SA
Date: 29-04-2016
Publisher: Wiley
Date: 14-06-2016
DOI: 10.1111/ANS.13616
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 17-04-2013
Abstract: The second hyper-reflective on spectral domain optical coherence tomography (SD-OCT) has been suggested to correlate with the photoreceptor inner segment ellipsoids (ISe). The purpose of our study was to determine the relationship between the intensity of the ISe band and retinal function measured by multifocal electroretinography (mfERG) in patients with early age-related macular degeneration (AMD). A high-resolution horizontal line scan through the fovea on SD-OCT and an mfERG recording were performed in one eye of 29 early AMD and 31 control participants. The relative intensity of the ISe band within 1000 μm of the fovea was quantified using ImageJ. The relationships between the relative intensity of the ISe band and the mfERG response parameters (P1 litude and implicit time) within the three central hexagons along the horizontal axis were determined. In normal participants, the relative intensity of the ISe band was significantly correlated with age (r = -0.634, P < 0.001) and also exhibited a topographic variation. On average, the relative intensity of the ISe band was significantly lower in patients with early AMD (1.77 ± 0.26) compared to control subjects (1.95 ± 0.27, P < 0.001) of a similar age range. The relative intensity of the ISe band was correlated significantly with the mfERG P1 implicit time (r = -0.745, P < 0.001), but not P1 litude (r = 0.144, P = 0.281). The relative intensity of the ISe band reduced with age and further in early AMD. The relative intensity was significantly correlated with mfERG P1 implicit time.
Publisher: Wiley
Date: 11-11-2013
DOI: 10.1111/CEO.12247
Abstract: A novel, ultra-low energy nanosecond laser (retinal rejuvenation therapy) has been developed with the aim to slow progression of early age-related macular degeneration (AMD). The safety, changes in fundus characteristics and macular function in a cohort of participants with bilateral intermediate AMD are reported. Prospective non-randomised, pilot intervention study. Subjects with bilateral intermediate AMD (n = 50, aged 50-75 years). Ultra-low energy laser pulses applied in 12 spots around the macula of one eye (0.15-0.45 mJ), using 400 μm diameter spot, 3 nanosecond pulse length, 532 nm wavelength and energy titrated to each patient. Best corrected visual acuity, drusen area and macular sensitivity (flicker perimetry) at baseline and at 3, 6 and 12 months post-laser. Treatment was painless with no clinically visible lesions. No participant developed choroidal neovascularization, while two with thin central retinal thickness at baseline developed atrophy at 12-month follow up. Drusen area was reduced in 44% of treated eyes and 22% of untreated fellow eyes, with changes in drusen and function not being coincident. Improvement in flicker threshold within the central 3° was observed in both the treated and untreated fellow eyes at 3 months post-laser. Of the 11 eyes at greatest risk of progression (flicker defect >15 dB), seven improved sufficiently to be taken out of this high-risk category. A single unilateral application of nanosecond laser to the macula produced bilateral improvements in macula appearance and function. The nanosecond retinal rejuvenation therapy laser warrants ongoing evaluation as an early intervention for AMD.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 29-11-2011
DOI: 10.1167/IOVS.11-8517
Abstract: To determine the retinal function in early age-related macular degeneration (AMD) assessed by the multifocal electroretinogram (mfERG) and flicker perimetry and to seek a relationship between local objective mfERG parameters and subjective flicker perimetry thresholds. mfERG and flicker perimetry were performed in 15 patients (15 eyes) with early AMD and 14 controls (14 eyes) of similar age. The mfERG P1 response litude density (nV/deg²) and P1 implicit time of the first-order kernel and the flicker thresholds of each concentric ring were analyzed. The relationship between in idual mfERG responses and the corresponding in idual flicker sensitivity outcomes was determined. The mfERG response litude of the central ring (ring 1) was significantly reduced in early AMD eyes compared with the controls (P = 0.009). No significant difference in mfERG litude between early AMD and control eyes was detected in the other rings. The mfERG implicit time was significantly increased in the early AMD eyes but only within the central four rings of 12°. A significant reduction in flicker sensitivity was also detected in early AMD eyes but only within the central 6°. There was a significant, moderate correlation (r = -0.477 P < 0.001) between local mfERG latency and flicker sensitivity from the same tested locations within the central 6°. There was a weak correlation (r = 0.200 P = 0.014) between mfERG litude and flicker sensitivity. Both mfERG and flicker perimetry show abnormal retinal function, but only in the very central macula, in early AMD. A novel relationship between mfERG and flicker sensitivity should enhance the clinical monitoring of disease progression.
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.OPHTHA.2014.02.005
Abstract: To compare the effectiveness of low-luminance visual acuity (LLVA) and microperimetry as functional measures in early stages of age-related macular degeneration (AMD). Prospective cross-sectional study. One hundred seventy-nine participants with a clinical spectrum of non-neovascular AMD and 26 control participants. Best-corrected visual acuity (BVCA), LLVA, and microperimetric retinal sensitivity were measured on 1 eye of all participants. Low-luminance deficit (LLD) was calculated as the difference between LLVA and BCVA. The functional parameters were compared between 6 clinical severity groups (from controls to non-foveal geographic atrophy [GA]), and the relationships and magnitude of these parameters were determined and compared. Visual acuity parameters (BCVA, LLVA, and LLD) and central retinal sensitivity. Best-corrected visual acuity, LLVA, and central retinal sensitivity were reduced significantly for all AMD clinical severity groups when compared with control participants (P ≤ 0.002), except for those with drusen between 63 and 125 μm (P ≥ 0.107). However, LLD was not significantly different from control participants in all groups (P ≥ 0.073), except in the non-foveal GA group (P = 0.008). A significant positive relationship between central retinal sensitivity and LLD (R = 0.613 P < 0.001), but not BCVA, suggests that there is a trend for LLVA to detect a greater extent of functional deficit than BCVA in eyes with increasingly poorer retinal sensitivity. However, the results of the linear regression models estimated central retinal sensitivity to be 6.1, 3.7, and 5.1 standard deviations (SDs) less than normal by the time BCVA, LLVA, and LLD, respectively, were 2 SDs less than normal. In early stages of AMD, LLVA did not detect a greater extent of functional deficit than BCVA when compared with control participants. Although there was a trend for LLVA to be more effective at detecting foveal deficits than BCVA in eyes with increasingly poorer retinal sensitivity, both visual acuity measures were much less sensitive compared with microperimetry.
Publisher: Future Medicine Ltd
Date: 08-2014
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2016
DOI: 10.1097/OPX.0000000000000891
Abstract: This study aimed to determine the feasibility of an assessment of vision-related orientation and mobility (O& M) tasks in persons with severe vision loss. These tasks may be used for future low vision rehabilitation clinical assessments or as outcome measures in vision restoration trials. Forty legally blind persons (mean visual acuity logMAR 2.3, or hand movements) with advanced retinitis pigmentosa participated in the Orientation & Mobility—Very Low Vision (O& M-VLV) subtests from the Low Vision Assessment of Daily Activities (LoVADA) protocol. Four categories of tasks were evaluated: route travel in three indoor hospital environments, a room orientation task (the “cafe”), a visual exploration task (the “gallery”), and a modified version of the Timed Up and Go (TUG) test, which assesses re-orientation and route travel. Spatial cognition was assessed using the Stuart Tactile Maps test. Visual acuity and visual fields were measured. A generalized linear regression model showed that a number of measures in the O& M-VLV tasks were related to residual visual function. The percentage of preferred walking speed without an aid on three travel routes was associated with visual field (p 0.01 for all routes) whereas the number of contacts with obstacles during route travel was associated with acuity (p = 0.001). TUG-LV task time was associated with acuity (p = 0.003), as was the cafe time and distance traveled (p = 0.006 and p 0.001, respectively). The gallery score was the only measure that was significantly associated with both residual acuity and fields (p 0.001 and p = 0.001, respectively). The O& M-VLV was designed to capture key elements of O& M performance in persons with severe vision loss, which is a population not often studied previously. Performance on these tasks was associated with both binocular visual acuity and visual field. This new protocol includes assessments of orientation, which may be of benefit in vision restoration clinical trials.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 19-11-2013
Abstract: To determine the relationship between axial length (AL), retinal function, and relative oxygen (O₂) consumption to better understand the protective effect of axial elongation on diabetic retinopathy development. Measurements of AL, multifocal electroretinogram (mfERG), and relative O₂ consumption (difference between arteriolar and venular O₂ saturation levels or A-V difference) were performed on 50 healthy in iduals. The relationships between AL, mfERG litude, and A-V difference were analyzed using linear regression models. Path analysis was performed to determine the direct and indirect effects (via mfERG litude) of AL on A-V difference. mfERG P1 litude was positively associated with A-V difference (β = 0.33 95% confidence interval [CI]: 0.23-0.42). Increased AL was significantly associated with a decrease in A-V difference (β = -1.08 95% CI: -1.52 to -0.65) as well as a decrease in retinal function (β = -3.14, 95% CI: -4.07 to -2.20). Path analysis models including AL (study factor), retinal function (intermediate variable), and A-V difference (outcome variable) showed that AL had little direct association with A-V difference (β(p) = -0.002), while the indirect effect of AL on A-V difference via changes in retinal function were substantial (β(p) = -0.51). In eyes with longer AL, the reduction in A-V difference is explained by the parallel reduction in retinal function. These findings suggest that longer eyes have decreased retinal function and O₂ consumption, and thus are relatively less hypoxic in the presence of diabetes, which may partly explain the reduced risk of DR in these eyes.
Publisher: EDP Sciences
Date: 2019
DOI: 10.1051/EPJCONF/201921402046
Abstract: We report on developments of the Geant4 electromagnetic physics sub-libraries of Geant4 release 10.4 and beyond. Modifications are introduced to the models of photoelectric effect, bremsstrahlung, gamma conversion, single and multiple scattering. The theory-based Goudsmit-Saunderson model of electron ositron multiple scattering has been recently reviewed and a new improved version, providing the most accurate results for scattering of electrons and positrons, was made available. The updated interfaces, models and configurations have already been integrated into LHC applications and may be useful for any type of simulations.
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.ORET.2022.06.001
Abstract: The relative ellipsoid zone reflectivity (rEZR) has been reported to be reduced in intermediate age-related macular degeneration (iAMD). However, longitudinal changes in rEZR remain unknown. This study investigated the natural history of rEZR in iAMD and its association with risk factors for disease progression including the presence and/or extent of drusen volume, reticular pseudodrusen (RPD) and pigmentary abnormalities (PA). Longitudinal observational study. Subjects with bilateral large drusen. Spectral-domain optical coherence tomography (SD-OCT) images of both eyes from each participant were obtained every 6 months for 3 years. Using an automated rEZR determination approach, the average rEZR of the central 20° macula was determined for each SD-OCT volume scan. Linear mixed models were used to determine the rate of change in rEZR with age (using the cross-sectional data at baseline) and over time (longitudinal data), and the interactions between the rate of rEZR changes with AMD risk factors at baseline. rEZR and its rate of change with age and over time. A total of 280 eyes from 140 in iduals with bilateral large drusen were included in this study. Cross-sectional data showed that the rEZR was reduced with increasing age (-8.4 arbitrary units [AU] per decade, 95% CI: -11.5 to -5.2, p < 0.001). The longitudinal data showed that, on average, the rEZR declined at a rate of -2.1 AU per year (95% CI = -2.6 to -1.6 AU per year p < 0.001). Both the presence of RPD (p = 0.032) and larger RPD area (p = 0.042) at baseline were associated with a faster rate of rEZR decline over time, while the presence of PA and the drusen volume at baseline showed no significant association with the rEZR decline over time (p = 0.529 and p = 0.068, respectively). The rEZR significantly reduces over 3 years in subjects with iAMD, and that both the presence and increasing extent of coexistent RPD at baseline is associated with a faster rate of decline. These findings warrant further studies to understand the value of the rEZR as a biomarker of AMD progression.
Publisher: American Medical Association (AMA)
Date: 04-2015
DOI: 10.1001/JAMAOPHTHALMOL.2014.5963
Abstract: There is a need for more sensitive measures of disease in intermediate age-related macular degeneration (AMD) to evaluate novel interventions more effectively and expediently. To determine if microperimetry and low luminance visual acuity can detect functional changes over a short duration of follow-up. Prospective longitudinal examination of 49 participants with consecutive AMD and 10 healthy participants in a research clinic from May 1, 2012, to December 31, 2013. Forty-one participants had intermediate AMD, 8 had nonfoveal geographic atrophy due to AMD. Participants underwent microperimetry examinations in 1 eye during a 12-month period at 6-month intervals for participants with AMD and at baseline and 12 months for control participants low luminance visual acuity was performed at baseline and at 12 months for all participants. Changes in pathological features of intermediate AMD eyes were determined using side-by-side comparisons of color fundus photographs from the initial and final visit as remaining stable, progressed, or improved. Microperimetric sensitivity and low luminance visual acuity. A reduction in mean (SE) microperimetric pointwise sensitivity was identified at 12 months compared with the baseline for intermediate AMD eyes graded as stable (-0.31 dB [0.10 dB] P = .003) or worsened (-0.42 dB [0.12 dB] P < .001) and an improvement in mean (SE) pointwise sensitivity was identified in eyes graded as improved (1.13 dB [0.23 dB] P < .001). A reduction in mean (SE) pointwise sensitivity was identified in eyes with nonfoveal geographic atrophy at both 6 months (-1.41 dB [0.22 dB] P < .001) and 12 months compared with the baseline (-2.56 dB [0.22 dB] P < .001) while a change in mean (SE) pointwise sensitivity was not identified over the 12-month period for control participants (-0.11 dB [0.11 dB] P = .34). No changes in best-corrected visual acuity or low luminance visual acuity were identified in all groups over the 12-month period (P ≥ .07). Microperimetry detected subtle changes in visual function over a 12-month period in eyes with intermediate AMD but visual acuity measures did not identify any such changes. These findings suggest that microperimetry is worth exploring as a method for assessing the efficacy of novel interventions for intermediate AMD potentially requiring a shorter duration of follow-up.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 28-03-2013
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 21-03-2016
Abstract: To determine the prevalence of reticular pseudodrusen (RPD) and their detection using multimodal imaging in patients with bilateral large drusen, and examine their clinical, demographic, environmental, and genetic associations. Three hundred participants with bilateral large drusen (>125 μm) underwent color fundus photography (CFP), near-infrared reflectance (NIR), fundus autofluorescence (FAF), and spectral-domain optical coherence tomography (SD-OCT) imaging. Demographic information, smoking, and medical history were recorded, and a blood s le was obtained and genotyped to identify the risk alleles of the CFH and ARMS2 genes. Reticular pseudodrusen were detected in 28.2% eyes of 29.0% participants using NIR and SD-OCT combined, but CFP and FAF detected only 42% and 89%, respectively, of these eyes with RPD. Participants with RPD were significantly older than those without (P 0.173). However, the minor allele frequency of the ARMS2 gene was significantly higher in participants with RPD (P = 0.002). The presence of RPD was also independently associated with the presence of atrophic changes (including nascent geographic atrophy and drusen-associated atrophy detected on SD-OCT P = 0.043). Reticular pseudodrusen were detected on NIR and SD-OCT in more than a quarter of participants with bilateral large drusen, being often overlooked with CFP. Those with RPD had a higher frequency of the ARMS2 risk variant, and eyes with RPD were more likely to have atrophic changes. These findings are important to consider when managing patients with intermediate AMD.
Publisher: Wiley
Date: 12-11-2014
DOI: 10.1096/FJ.14-262444
Abstract: Age-related macular degeneration (AMD) is a leading cause of vision loss, characterized by drusen deposits and thickened Bruch's membrane (BM). This study details the capacity of nanosecond laser treatment to reduce drusen and thin BM while maintaining retinal structure. Fifty patients with AMD had a single nanosecond laser treatment session and after 2 yr, change in drusen area was compared with an untreated cohort of patients. The retinal effect of the laser was determined in human and mouse eyes using immunohistochemistry and compared with untreated eyes. In a mouse with thickened BM (ApoEnull), the effect of laser treatment was quantified using electron microscopy and quantitative PCR. In patients with AMD, nanosecond laser treatment reduced drusen load at 2 yr. Retinal structure was not compromised in human and mouse retina after laser treatment, with only a discrete retinal pigment epithelium (RPE) injury, and limited mononuclear cell response observed. BM was thinned in the ApoEnull mouse 3 mo after treatment (ApoEnull treated 683 ± 38 nm, ApoEnull untreated 890 ± 60 nm, C57Bl6J 606 ± 43 nm), with the expression of matrix metalloproteinase-2 and -3 increased (>260%). Nanosecond laser resolved drusen independent of retinal damage and improved BM structure, suggesting this treatment has the potential to reduce AMD progression.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-03-2014
Abstract: Vision restoration is a fast-approaching reality for some people with profound vision loss. In order to reliably determine treatment efficacy, accurate assessment of baseline residual visual function is critical. The purpose of this study was to compare residual function as detected on Goldman visual field (GVF) and full-field ERG (ffERG), and correlate with the remaining photoreceptor layer as determined by spectral-domain optical coherence tomography (SD-OCT), in subjects with severe vision loss. Fifty-four subjects with advanced retinitis pigmentosa and no discernible signal on ffERG were included. Trace residual function was assessed using discrete Fourier transform (DFT) analysis of the 30-Hz flicker ffERG and the percentage of remaining GVF. The horizontal extent of the outer nuclear layer (ONL) on SD-OCT was assessed. Thirty percent of the study eyes had a 30-Hz flicker response after DFT analysis of the ffERG, and 57% had a measurable GVF. Thirty-five percent had a visible ONL on SD-OCT. There was no significant correlation between the magnitude of the 30-Hz flicker response and the percentage of remaining GVF (r = 0.172, P = 0.213) or the extent of remaining central photoreceptors (r = 0.258, P = 0.06). Only 17% of the eyes had all three parameters detected. Discrete Fourier transform analysis of the 30Hz-flicker ffERG response and GVF can detect trace residual function. Evidence of this residual function is not always supported by the structural correlate of a measurable ONL. Our findings highlight the importance of completing a multimodal assessment to accurately define the important parameters of retinal structure and function in people with profound vision loss.
Publisher: Springer Science and Business Media LLC
Date: 11-03-2005
DOI: 10.1007/S00417-005-1156-3
Abstract: Vogt-Koyanagi-Harada (VKH) disease presents with anterior segment inflammation, choroiditis and exudative retinal detachment. Following resolution of the inflammation, VKH patients have been noted to complain of visual disturbances despite good visual acuity. We therefore investigated the visual function deficits of convalescent VKH patients. A cross-sectional observational nonrandomized controlled study of convalescent VKH patients from the Uveitis Service of the Singapore National Eye Centre, and normal subjects was performed. The best-corrected visual acuities (BCVA) and multifocal electroretinograms (mfERGs) of VKH patients with and without peripapillary atrophy (PPA) were compared with those of the normal eyes. The mfERG results were sub ided into those obtained from the peripapillary area and those from the rest of the macular. Eleven VKH eyes with large PPA to disc ratios (PPA/D ratio >2), 15 VKH eyes with PPA/D ratios 2 had a BCVA of less than 20/40. All the other eyes had 20/20 vision. Nine of the 11 VKH eyes with PPA/D>2 also had large areas of chorioretinal atrophy. The mfERG responses of VKH eyes with PPA/D ratio >2 were markedly reduced in litude (p<0.001) and delayed in implicit time (p<0.001) throughout the entire macular area. VKH patients with PPA/D ratio<1 had significantly reduced mfERG litudes throughout the entire macular area, as well as delayed implicit times at the peripapillary region (p=0.026). Sub- ision of VKH eyes with PPA/D<1 into eyes with no PPA and eyes with a small PPA, showed that both groups had a similar reduction in response litude over the entire macular region. However, the implicit time was significantly delayed in eyes with small PPA when compared to those without PPA (p<0.03). VKH patients with large PPA have clinically significant visual dysfunction. VKH patients without PPA also have subclinical retinal dysfunction. The mfERG may be a useful adjunct in the management of VKH by detecting early retinal damage.
Publisher: Wiley
Date: 24-05-2002
DOI: 10.1046/J.1442-9071.2002.00517.X
Abstract: The non-linearities of the diffuse flash visual evoked potential (VEP) have been shown to generate separable waves corresponding to Magnocellular and Parvocellular contributions. The authors wished to investigate whether, under conditions of isoluminance, the chromatic pattern appearance VEP shows waveforms that are related to both the processing of contours (the pattern) and the processing of the diffuse stimulation (from the area lying between the contours). The VERIS multifocal system was used to record monocular VEP. Standard 2-ring, 3-ring, 5-ring and 7-ring VERIS pattern stimuli were employed with a cardboard circular aperture used to blank the stimulus monitor to a 9-cm diameter field. The results for four subjects were recorded. The first order kernel responses showed a significant increase in litude with total contour length. In comparison, the litudes of the first and second slices of the second order kernel did not increase with contour length. It appears that the contour-dependent component has negligible non-linear components. It is proposed that the constant, non-zero responses of the higher order kernel components reflects contributions from the diffuse chromatic VEP.
Publisher: IEEE
Date: 09-2013
Publisher: Wiley
Date: 14-03-2011
DOI: 10.1002/PATH.2858
Abstract: Hypoxic injury, including that resulting in the retinopathy of prematurity, may induce retinal ganglion cell (RGC) death in the neonatal retina. We hypothesized that this may be mediated by excess production of tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) by microglia. One-day-old Wistar rats were subjected to hypoxia for 2 h and the expression of TNF-α and IL-1β and their receptors was determined in the retina. The mRNA and protein expression of TNF-α, IL-1β, TNF-receptor 1 (TNF-R(1)), and IL-1 receptor 1 (IL-1R(1)) and the tissue concentration of TNF-α and IL-1β were up-regulated significantly after the hypoxic exposure. TNF-α and IL-1β immunoreactivity was localized in microglial cells, whereas that of TNF-R(1) and IL-1R(1) was restricted to RGCs, as confirmed by double immunofluorescence labelling. Along with this, increased expression of monocyte chemoattractant protein-1 and its receptor CCR2 was detected in the microglia. Primary cultured microglia subjected to hypoxia showed enhanced release of TNF-α and IL-1β. Primary cultured retinal ganglion cells (RGCs) treated with conditioned medium derived from hypoxic microglia showed enhanced apoptosis, which was significantly reduced when the cells were treated with microglia conditioned medium neutralized with TNF-α/IL-1β antibody. Our results suggest that activated microglial cells in hypoxic neonatal retina produce increased amounts of TNF-α and IL-1β that could induce RGC death.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 2010
DOI: 10.1167/IOVS.09-4069
Abstract: To assess retinal function in in iduals with type 2 diabetes with no retinopathy or nonproliferative diabetic retinopathy (NPDR) and determine the relationship between retinal function and retinal vascular caliber. A full-field electroretinogram (ERG) and retinal vascular caliber measurements were performed in subjects with nonproliferative diabetic retinopathy (NPDR, n = 10), diabetic subjects without retinopathy (no-DR, n = 18), and normal control subjects (n = 18). The response litudes and implicit times of scotopic and photopic ERG and the retinal arteriolar and venular calibers were compared among the study groups. The relationships between ERG parameters and retinal vascular calibers were determined. There were statistically significant differences between diabetic (no-DR and NPDR groups) and control subjects in the litudes and implicit times of rod-derived ERG responses, but not in the cone-derived ERG responses. All the oscillatory potential (OP) components (OP1-OP4) were significantly reduced in litude and increased in implicit time in the no-DR and NPDR groups. No significant difference was found in any of the ERG parameters between the no-DR and NPDR groups. Of all the ERG parameters examined, only OP4 litude correlated significantly with the retinal arteriolar caliber (r = -0.556, P = 0.006). None of the OP components correlated significantly with retinal venular caliber. Significant retinal dysfunction was demonstrated in all diabetic patients, even in those without clinically detectable retinopathy, with the rod system being predominantly affected. OP4 litude correlates with retinal arteriolar caliber in diabetic patients, suggesting a correlation between retinal neuronal dysfunction and microvasculature changes.
Publisher: Elsevier BV
Date: 08-2007
DOI: 10.1016/J.OPHTHA.2006.11.030
Abstract: To investigate the multifocal electroretinogram (mfERG) in myopic children in relation to the rate of myopia progression. Observational study. Eighty-one school children with myopia. Cycloplegic refraction, ocular biometry, and mfERG recordings were performed in myopic children aged 9 to 11 years in 2002. The refraction and ocular biometry assessments were repeated 2 years later in 2004. The 2-year myopia progression rate was calculated for a randomly selected eye of each in idual. The mfERG parameters recorded at the initial visit in 2002 were compared with subsequent progression rates. First-order kernel mfERG responses. Of the 81 eyes, 12 eyes had a high progression rate (defined as a progression rate of >1 diopter [D]/2 years), 44 eyes had a moderate progression rate (progression rate of >0.25 D but < or =1 D/2 years), and 25 eyes showed no progression or a low progression rate (progression rate of < or =0.25 D/2 years). The P1 litude of the mfERG in the high progression group was significantly smaller than that in the moderate (P = 0.023) and non/low-progression groups (P = 0.030) but only within the central 5 degrees (ring 1). None of the other mfERG parameters of the central ring were significantly different among the groups. The mfERG parameters of the outer rings were similar in all groups. Decreased foveal function as determined by the mfERG is associated with a high rate of myopia progression. Electrophysiologic examination of central retinal function may predict the progression and severity of myopia in school children.
Publisher: Wiley
Date: 28-08-2014
DOI: 10.1111/CEO.12387
Abstract: There are limited data available on the variables that might affect retinal vessel oxygen saturation (SO₂) in diabetes. Therefore, the aim of this study is to assess factors associated with retinal oximetry values in persons with diabetes. Clinic-based cross-sectional study. Fifty-eight persons with diabetes aged 18+ years, recruited from the University of Melbourne, the Royal Victorian Eye and Ear Hospital, and St. Vincent's Hospital (Melbourne), Australia. Retinal oximetry was performed using the oximetry module of the Vesselmap system (Imedos UG, Jena, Germany) in 92 diabetic eyes. Generalized estimating equation models were used to estimate the associations between candidate variables (age gender retinal capillary flow duration of diabetes hypertension smoking status presence of diabetic retinopathy [DR] glycated haemoglobin triglyceride total cholesterol finger SO₂ and ocular perfusion pressure) with retinal oximetry measures. Arteriolar SO₂, venular SO₂ and the arterio-venous (A-V) difference. Of the candidate factors assessed, only the presence of DR was significantly associated with increased venular SO₂ and decreased A-V difference in unadjusted analyses. In models adjusting for age and gender and significant variables from unadjusted analyses, compared with no DR, the presence of DR was significantly associated with greater retinal venular SO₂ values (β = 3.65%, 95% confidence interval: 0.67-6.63%) and decreased A-V difference (β = -2.00%, 95% confidence interval: -3.46 to -0.53%). In patients with diabetes, eyes with DR were associated with increased venular SO₂ and decreased A-V difference compared with eyes without DR, suggesting an altered metabolic state in DR.
Publisher: IOP Publishing
Date: 18-05-2010
DOI: 10.1088/1741-2560/7/3/036008
Abstract: Several approaches have been proposed for placement of retinal prostheses: epiretinal, subretinal and suprachoroidal. We aimed to systematically evaluate the effectiveness of varying a range of stimulus parameters and electrode geometry for a suprachoroidal electrode array, using cortical evoked responses to monopolar electrical stimulation in cats. Our results indicate that charge thresholds were not dependent on electrode size, pulse widths or position of the return electrode tested, but were dependent on the number of sites stimulated in parallel. Further, we found that the combination of monopolar stimulation with large diameter electrodes, wide pulse widths and parallel stimulation minimized the voltage requirements for stimulation. These results provide useful insights for the design specifications of a low voltage suprachoroidal stimulator.
Publisher: Springer Science and Business Media LLC
Date: 15-09-2008
Abstract: To determine the correlation between systemic corticosteroid therapy and the occurrence and size of peripapillary atrophy (PPA) in patients with Vogt-Koyanagi-Harada (VKH) disease. All patients with VKH disease were retrospectively reviewed for their corticosteroid regimen. The extent of the PPA, if present, was measured using digitized imaging software, by two masked observers. Eyes with myopia greater than 6 dioptres or glaucoma were excluded. The patients were classified into three groups: early high (EH), late high (LH), and low dose (LD), according to the dose and timing of corticosteroids received during the acute phase of the disease. There were 40 eyes in the EH group, 25 eyes in the LH group, and 23 eyes in the LD group. Multivariate analysis showed that corticosteroid therapy was the main determinant of PPA occurrence. All the eyes in the LD group had PPA and eyes in the LH groups were 4.02 times (95% confidence interval 1.24-13.07) more likely to develop PPA than those in the EH group. The LD group also had larger PPA to disc ratios than the EH group. (Mean of 2.83 vs0.19, P<0.001). The development and extent of PPA in patients with VKH disease appear to be dependent on the dose and timing of systemic corticosteroids.
Publisher: Informa UK Limited
Date: 02-2013
DOI: 10.1586/EOP.12.71
Publisher: Wiley
Date: 10-10-2014
DOI: 10.1111/CEO.12428
Abstract: A key requirement for retinal prostheses is the ability for safe removal or replacement. We examined whether suprachoroidal electrode arrays can be removed or replaced after implantation. Suprachoroidal electrode arrays were unilaterally implanted into 13 adult felines. After 1 month, arrays were surgically explanted (n = 6), replaced (n = 5) or undisturbed (n = 2). The retina was assessed periodically using fundus photography and optical coherence tomography. Three months after the initial implantation, the function of replaced or undisturbed arrays was assessed by measuring the responses of the visual cortex to retinal electrical stimulation. The histopathology of tissues surrounding the implant was examined. Array explantation or replacement was successful in all cases. Fundus photography showed localized disruption to the tapetum lucidum near the implant's tip in seven subjects following implantation. Although optical coherence tomography showed localized retinal changes, there were no widespread statistically significant differences in the thickness of the retinal layers or choroid. The distance between the electrodes and retina increased after device replacement but returned to control values within eight weeks (P < 0.03). Staphylomas developed near the scleral wound in five animals after device explantation. Device replacement did not alter the cortical evoked potential threshold. Histopathology showed localized outer nuclear layer thinning, tapetal disruption and pseudo-rosette formation, but the overall retinal morphology was preserved. It is feasible to remove or replace conformable medical grade silicone electrode arrays implanted suprachoroidally. The scleral wound requires careful closure to minimize the risk of staphylomas.
Publisher: Wiley
Date: 11-2013
DOI: 10.1111/JPI.12016
Abstract: The purpose of this study was to determine whether melatonin treatment would mitigate retinal ganglion cell (RGC) death in the developing retina following a hypoxic insult. Lipid peroxidation (LPO), glutathione (GSH), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) concentrations, expression of vascular endothelial growth factor receptors, Flt-1 and Flk-1, release of cytochrome c from mitochondria, and caspase-3 expression were examined in the retinas of 1-day-old rats at 3 hr to 14 days after a hypoxic exposure. The mRNA and protein expression of Flt-1 and Flk-1 and the tissue concentration of LPO, TNF-α, and IL-1β were upregulated significantly after the hypoxic exposure, whereas the content of GSH was decreased significantly. RGC cultures also showed increased LPO and decreased GSH levels after hypoxic exposure but these effects were reversed in cells treated with melatonin. TNF-α and IL-1β expression was specifically located on microglial cells, whereas Flt-1 and Flk-1 was limited to RGCs as confirmed by double immunofluorescence labeling. Cultures of hypoxic microglial cells treated with melatonin showed a significant reduction in the release of these cytokines as compared to untreated hypoxic cells. Hypoxia induced increase in the cytosolic cytochrome c and caspase-3 in RGCs was attenuated with melatonin treatment. The results suggest that, in hypoxic injuries, melatonin is neuroprotective to RGCs in the developing retina through its antioxidative, anti-inflammatory, and anti-apoptotic effects. Melatonin suppressed Flt-1 and Flk-1 expression in retinal blood vessels, which may result in reduced retinal vascular permeability and it also preserved mitochondrial function as shown by a reduction in cytochrome c leakage into the cytosol. The results may have therapeutic implications for the management of retinopathy of prematurity.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-12-2013
Abstract: To determine whether progressive ametropia can be induced in chicks and reversed by manipulation of the chromaticity of ambient light. One-day-old chicks were raised in red light (90% red, 10% yellow-green) or in blue light (85% blue, 15% green) with a 12 hour on/off cycle for 14 to 42 days. Refraction was determined by streak retinoscopy, and by automated infrared photoretinoscopy and ocular biometry by A-scan ultrasonography. Red light induced progressive myopia (mean refraction ± SD at 28 days, -2.83 ± 0.25 diopters [D]). Progressive hyperopia was induced by blue light (mean refraction at 28 days, +4.55 ± 0.21 D). The difference in refraction between the groups was highly significant at P < 0.001. Induced myopia or hyperopia was axial as confirmed by ultrasound biometry. Myopia induced by 21 days of red light (-2.21 ± 0.21 D) was reversed to hyperopia (+2.50 ± 0.29 D) by subsequent 21 days of blue light. Hyperopia induced by 21 days of blue light (+4.21 ± 0.19 D) was reversed to myopia (-1.23 ± 0.12 D) by 21 days of red light. Rearing chicks in red light caused progressive myopia, while rearing in blue light caused progressive hyperopia. Light-induced myopia or hyperopia in chicks can be reversed to hyperopia or myopia, respectively, by an alteration in the chromaticity of ambient light. Manipulation of chromaticity may be applicable to the management of human childhood myopia.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 14-10-2014
Abstract: To correlate and compare retinal function measured using multifocal electroretinography (mfERG) with microperimetry in intermediate age-related macular degeneration (AMD). Sixty AMD participants underwent multifocal electroretinography (mfERG) and microperimetry testing in one eye, and 44 control participants were included to provide normative values for each test. Thirteen hexagons in the central three rings of a 103-hexagon stimulus grid for mfERG and retinotopically matched points on microperimetry were chosen and converted into standard deviations (SDs) away from that of normal participants (Z-score) to represent the magnitude of measured functional deficit and to allow a comparison of the two measures. For the average of all points on mfERG and microperimetry, mfERG N1 to P1 response litude and microperimetric retinal sensitivity was significantly lower (P = 0.013 and P < 0.001, respectively) and mfERG P1 implicit time was significantly increased (P < 0.001) in the AMD participants compared to those in the control participants. Considering retinotopically matched points, there was no significant correlation between the average Z-scores of the microperimetric retinal sensitivity and mfERG implicit time (correlation coefficient, R = 0.254, P = 0.051), nor response litudes (R = 0.006, P = 0.965), and the measured functional deficit with microperimetry was consistently greater than both mfERG parameters (P < 0.001). The measured functional deficit with microperimetry was greater than mfERG parameters in eyes with intermediate AMD. The absence of correlations between these two measures suggests that mfERG may be capturing unique aspects of retinal dysfunction. These findings are important when considering the use of these functional measures in intermediate AMD.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 20-03-2014
Abstract: To assess factors associated with retinal oximetry values in healthy young adults. Retinal oximetry readings were assessed using the oximetry module of the Vesselmap System in 100 eyes of 50 healthy subjects aged 18 to 58 years. Generalized estimating equation models were used to estimate the associations of candidate variables (age, sex, retinal capillary flow, HbA1c, triglyceride, total cholesterol, ocular perfusion pressure, and finger oxygen saturation [SO2]) with retinal oximetry measures (arteriolar SO2, venular SO2, and the arterio-venous [A-V] difference). Of the candidate factors assessed, only age and finger SO2 were found to be significantly associated with one or more measures of retinal oximetry in unadjusted analyses. After adjusting for age, sex, and significant factors from unadjusted analyses, age and finger SO2 values remained significant. Age was associated with retinal arteriolar and venular SO2 values (per year increase in age, β = 0.31, 95% confidence interval [CI]: 0.15-0.48 and β = 0.26, 95% CI: 0.08-0.43, respectively), but not associated with the A-V difference. Finger SO2 values were associated with retinal arteriolar SO2 and A-V difference (per percentage change in finger SO2, β = 1.34, 95% CI: 0.40-2.28 and β = 0.74, 95% CI: 0.36-1.11, respectively), but not with venular SO2. In healthy young adults, age was positively associated with the retinal arteriolar and venular SO2 values, whereas finger SO2 was positively correlated with greater arteriolar SO2 and A-V difference. Our findings serve as a basis for future studies assessing retinal oximetry values in young adults under normal and pathophysiological conditions.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 27-06-2016
Abstract: To characterize the mouse retina lacking fatty acid binding protein (FABP7-/-). Immunohistochemistry (IHC) was performed in 8-week-old mice to localize FABP7 in the retina. Retinal thickness was measured using image-guided spectral-domain optical coherence topography images. Electroretinography was carried out to assess retinal function. Fundus photography and fundus fluorescein angiography were performed on FABP7-/- and littermate wild-type (WT) mice, and retinal vascular changes were calculated using Singapore I Vessel Assessment (SIVA) analysis. Blood glucose levels were measured in the 8-week-old WT and FABP7-/- mice. In addition, retina was processed for trypsin digestion and retinal flat mounts for isolectin staining. Transcript levels of FABP7, VEGF, GFAP, and Na+K+ATPase were quantified using real-time PCR, and protein expression was analyzed by IHC and Western blot. Fatty acid binding protein 7 is expressed in the inner nuclear layer, outer plexiform layer, and photoreceptor inner segments. No significant difference in retinal thickness and ERG responses was observed between FABP7-deficient and WT retinas. FABP7-/- mice have significantly decreased retinal venular caliber retinal arteriolar fractal dimension compared with WT littermates. FABP7-/- mice showed significant increased areas of fluorescein leakage in the retina. FABP7-/- mice exhibited elevated high blood glucose levels compared with WT mice. Trypsin digested FABP7-/- mice retina showed increased acellular strands and endothelial cell drop outs, and reduced microvasculature branching compared with WT retina. FABP7-/- mice retina also have increased GFAP and VEGF expression. Fatty acid binding protein 7 is expressed in the retina and might play an important role in maintaining retinal vasculature.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 16-12-2014
Abstract: To determine the microperimetric retinal sensitivity in areas with nascent geographic atrophy (nGA) compared with other pathological features in eyes with intermediate AMD. Participants with bilateral intermediate AMD underwent microperimetry examinations and high-resolution spectral-domain optical coherence tomography (SD-OCT) scans in a prospective study. Twenty-two participants (24 eyes) identified as having a microperimetric stimulus s ling an atrophic area (nGA or drusen-associated atrophy detected on SD-OCT) in an eye were analyzed, using three neighboring nonatrophic regions (with or without AMD-associated features) in the same eye as reference areas. On average, the mean microperimetric retinal sensitivity was worse in areas with nGA than nonatrophic reference areas (P ≤ 0.008), but better than areas with drusen-associated atrophy (P = 0.008). Considering all the microperimetry points in an eye, there were only 6 out of 16 eyes (37.5%) where the retinal sensitivity over nGA was the worst performing point in the eye, while all eight out of eight eyes (100.0%) with an area of drusen-associated atrophy detected on SD-OCT had the worst-performing point over that area. Areas of nGA were characterized by worse microperimetric retinal sensitivity compared with nonatrophic areas in eyes with intermediate AMD, but better retinal sensitivity compared with areas of drusen-associated atrophy detected on SD-OCT. Areas of nGA were also not always the worst performing point in an eye. These findings further our understanding of the functional changes occurring in novel SD-OCT identified pathological changes in intermediate AMD.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 29-04-2015
Abstract: The purpose of this study was to examine the test-retest repeatability of microperimetric sensitivity at the border of deep scotomas. Thirty normal participants underwent two examinations, each on the Macular Integrity Assessment (MAIA) microperimeter and on the MP-1 microperimeter (four examinations in total). A customized stimulus pattern allowed microperimetric sensitivity to be measured at the border of the optic nerve head (ONH), which acted as a model for the border of a deep scotoma-and also at the macular and peripapillary region. There were no significant changes in average point-wise sensitivity (PWS) values between the two examinations for all three regions using the MAIA microperimeter (P ≥ 0.262). The PWS coefficient of repeatability (CoR) was ±12.99 dB at the border of the ONH, which was significantly larger than points in the macular and peripapillary regions (P > 0.001). A significant decrease in average PWS, using the MP-1 microperimeter at the macular and peripapillary region (P < 0.001), meant that the PWS CoR could not be determined in these regions. No significant changes in average PWS were observed at the border of the ONH (P = 0.223), and the PWS CoR was ±7.52 dB in this region. Microperimetric test-retest repeatability at the border of a deep scotoma was worse than at other areas of normal retina, and this highlights the limitation of applying a single estimate of test-retest repeatability to determine whether significant functional decline has occurred at the border of a deep scotoma.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 25-11-2014
Abstract: To develop and characterize a feline model of retinal degeneration induced by intravitreal injection of adenosine triphosphate (ATP). Nineteen normally sighted adult cats received 100 μL intravitreal injections of ATP with a final concentration of 11, 22, or 55 mM at the retina. Four animals were euthanized 30 hours after injection and retinal sections examined for apoptosis using a TUNEL cell death assay. In the remaining animals, structural and functional changes were characterized over a 3-month period using a combination of electroretinography (ERG) and optical coherence tomography (OCT). Using a TUNEL cell death assay, we detected widespread photoreceptor death 30 hours after injection with 55 mM intravitreal ATP. All concentrations of ATP caused loss of retinal function and gross changes in retinal structure within 2 weeks of injection. Intravitreal injection of ATP led to a rapid loss of rod photoreceptor function and a gradual loss of cone photoreceptor function within 3 months. Outer nuclear layer thickness was globally reduced by 3 months, with the inner nuclear layer including the retinal nerve fiber layer remaining intact. Structural abnormalities were observed, including focal retinal detachment with evidence of both intravitreal and intraretinal inflammation in some eyes. Development of an ATP-induced feline model of retinal degeneration provides a rapid and effective large-eyed animal model for research into vision restoration.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-2010
DOI: 10.1167/IOVS.09-4870
Abstract: To investigate the feasibility of creating an animal model of selective retinal capillary closure to mimic the capillary closure that occurs in diabetic retinopathy. Fluorescent microspheres of 10- or 15-μm diameter were delivered to one eye of anesthetized pigs via a customized cannula advanced through the carotid arterial system to the origin of the external ophthalmic artery that supplies blood to the eye in this species. After preliminary trials in 10 pigs, embolization was performed in one eye of 34 animals that were allowed to survive for 7, 14, or 28 days. Embolized eyes were assessed by fluorescein angiography, electroretinography (ERG), and, after enucleation, light (LM) and electron (EM) microscopy. The microspheres were detectable in the retina immediately after embolization, were restricted to the nerve fiber layer of the retina, and remained thereafter within the retina for periods up to 28 days. They effectively occluded embolized capillaries and some precapillary arterioles. No systemic or cerebral adverse effects were noted, thus allowing survival and subsequent follow-up. Embolization caused a reduction in the b-wave litude and the oscillatory potentials of the rod-cone bright-flash ERG but did not affect the litude of the a-wave. Embolization induced extracellular and intracellular edema confined to the inner and mid retina, and as a result the retinas of embolized eyes were thicker than those of fellow, nonembolized eyes. The outer retina and RPE were unaffected. This survival model of retinal embolization with microspheres should be useful in the study of the retinal effects of the capillary closure that may occur in diabetic eyes.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-03-2013
Abstract: The aim of our study was to determine whether IOP lowering in glaucomatous and ocular hypertensive (OHT) eyes leads to an improvement in the full-field photopic negative response (PhNR) of the electroretinogram. A prospective nonrandomized interventional cohort study was conducted. Patients with OHT or glaucomatous optic neuropathy were recruited, and photopic full-field electroretinograms (ERG) were performed at baseline and then repeated 1 to 2 months later. The change in PhNR litude was compared between those eyes that had a significant lowering in IOP (defined as >25% decrease from baseline or to a predetermined target IOP) during follow-up and those that did not. From a cohort of 30 eyes, 18 eyes had a significant reduction in IOP during follow-up (n = 18) and 12 eyes had no significant change in IOP (<25% reduction in IOP, n = 12). A significant increase in PhNR litude and the PhNR/b-wave litude ratios was observed in the reduced IOP group, but not in the IOP stable group for the two flash intensities used (2.25 and 3.00 cd.s/m(2)). The full-field PhNR litude provides a potentially reversible measure of inner retinal function that improves after IOP lowering. Further study now is required to assess its use as a measure of optic nerve health in glaucoma patients.
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.JPSYCHORES.2013.03.008
Abstract: Through the eyes of those depressed, the world may appear dull and gray. Visual contrast sensitivity has recently been reported to be lower in depressed patients compared to healthy controls. We aimed to examine the consistency of this finding and to explore the underlying retinal electrophysiology. Twenty subjects with major depressive disorder and 20 matched healthy controls were studied. Pattern electroretinogram (PERG) and subjective visual contrast test were used to assess visual contrast sensitivity. Full-field electroretinography (ffERG) was additionally used to assess retinal neurophysiology. Depression was diagnosed based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and depression severity was measured using standard psychometric scales. Visual contrast sensitivity was significantly lower in depressed patients compared to controls based on the Landolt C visual contrast test, but no difference was found between groups using PERG and ffERG. Greater severity of depressive symptoms correlated (r=0.49, p=0.001) with poorer visual contrast sensitivity. Depressed subjects had reduced visual contrast discrimination performance, but this finding could not be consistently determined using PERG. The neurobiological link between major depressive disorder and visual contrast sensitivity warrants further investigation.
Publisher: Elsevier BV
Date: 09-2015
Publisher: American Medical Association (AMA)
Date: 10-2006
DOI: 10.1001/ARCHOPHT.124.10.1421
Abstract: To assess visual function in patients with dengue maculopathy using electrophysiological tests. Fifteen consecutive patients with dengue fever who experienced vision loss between July 2004 and July 2005 were included in this review. Full-field electroretinograms (ERG), pattern ERGs, and multifocal ERGs were performed. The most common electrophysiological finding (60%, 9/15) was a normal or mildly abnormal full-field ERG with reduced pattern ERG P50 litude and abnormal mfERG. Typically, multifocal ERG demonstrated a focal area of decreased macular response (especially between the fovea and optic nerve). Pattern ERG suggested normal optic nerve function in all but 1 case. Four patients had more severely reduced full-field ERG responses with reduced a-wave litude (suggestive of photoreceptor dysfunction), 3 of whom had an electronegative maximal response (suggestive of additional postreceptor dysfunction). Repeat multifocal ERG showed little change in 7 patients and incomplete resolution in 2 patients over 3 to 10 months. Retinal dysfunction associated with dengue maculopathy was localized mainly around the foveal region. It appeared to affect the outer and middle retina more severely with relative sparing of the inner retina. Retinal dysfunction may persist for several months. Longer follow-up is required to determine whether these changes are permanent.
Publisher: Wiley
Date: 30-10-2013
DOI: 10.1111/J.1442-9071.2012.02867.X
Abstract: Little quantitative information exists regarding the effect that retinitis pigmentosa (RP) has on the choroid. The aim of this study was to determine choroidal thickness profiles in patients with RP. Prospective. Forty-two RP and 22 control subjects participated in the study. RP patients had mild to severe disease, with a visual acuity range of logMAR 0.1 to no light perception. Images of the retina and choroid were obtained using the enhanced depth-imaging method and optical coherence tomography (OCT). Choroidal thickness measures were determined via manual segmentation of the OCT image. The thickness profiles of the normal and RP groups were compared. The associations between choroidal thickness, visual acuity and duration of RP were determined. The choroid was thickest in the control eyes at the subfoveal location (336.60 ± 70.42 μm), and the thickness gradually decreased towards the peripheral retina (temporal 8° = 295.55 ± 60.52 μm nasal 8° = 251.68 ± 49.93 μm). In RP, the mean thickness was also greater at the fovea (215.60 ± 94.91 μm) than the temporal (191.66 ± 72.42 μm) and nasal (149.91 ± 57.42 μm) retina, but all values were significantly lower than those of the controls (P ≤ 0.001). Subfoveal choroidal thickness was significantly correlated with visual acuity (r = -0.46, P < 0.001) and duration of disease (r = -0.4, P = 0.001). Patients with RP have a thinner choroid than controls. Patients with poorer visual acuity or longer duration of symptoms tended to have thinner choroids. Knowledge of choroidal thickness profile in RP is important for the field of restorative vision research and the development of suprachoroidal retinal prostheses.
Publisher: MDPI AG
Date: 08-02-2017
DOI: 10.3390/IJMS18020345
Publisher: Public Library of Science (PLoS)
Date: 24-06-2015
Publisher: Elsevier BV
Date: 05-0004
Publisher: American Medical Association (AMA)
Date: 03-2006
DOI: 10.1001/ARCHOPHT.124.3.328
Abstract: To determine the correlation between multifocal electroretinogram (mfERG) parameters and the severity of myopia in adults and children. Observational study. Multifocal electroretinograms were recorded using the VERIS system from randomly selected eyes of 104 children and 31 adults with various degrees of myopia. Dawson, Trick, and Litzkow fiber electrodes were used and the pupil was dilated with 1% tropicamide. Subjective refraction was performed under cycloplegia and axial length measurement was determined by A-scan ultrasonography. The N1 (first negative trough), P1 (first positive peak), and N2 (second negative trough) components of the first-order kernel response of the mfERG were measured and correlated with the refractive data. First-order kernel mfERG responses. The N1, P1, and N2 litudes were significantly correlated with the severity of myopia in adult subjects (N1, r = 0.591, P = .001 P1, r = 0.682, P<.001 N2, r = 0.732, P<.001). The response litudes of N1, P1, and N2 decreased as the dioptric power of myopia increased. However, there were no significant correlations found between N1 (r = 0.073, P = .30), P1 (r = 0.071, P = .31), and N2 (r = 0.052, P = .46) litudes and the severity of myopia in children. The severity of myopia was also significantly correlated with N1 (r = -0.750, P<.001), P1 (r = -0.769, P<.001), and N2 (r = -0.664, P<.001) implicit times in adults with myopia, however, only the P1 (r = -0.166, P = .02) implicit time was significantly correlated with children with myopia. There is a significant correlation between the refractive error and mfERG litude in adults with myopia however, such a relationship is absent in children with myopia. These findings suggest that the severity of myopia has little influence on the ERG litude, at least in children.
Publisher: Elsevier
Date: 2011
Publisher: BMJ
Date: 02-2005
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-2009
DOI: 10.1167/IOVS.09-3552
Abstract: This study was undertaken to examine the effects of an acute hypoxic exposure on the retinal cells and production of vascular factors such as vascular endothelial growth factor (VEGF) and nitric oxide (NO), which may affect vascular permeability in the developing retina. Retinas of 1-day-old rats were examined at 3 hours to 14 days after hypoxic exposure. The mRNA and protein expression of hypoxia-inducible factor-1alpha (HIF-1alpha), VEGF, endothelial nitric oxide synthase (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS) were determined by real-time RT-PCR, Western blot analysis, and immunohistochemistry. Electron microscopy was used to examine the structural alterations in retinal cells, and rhodamine isothiocyanate (RhIC) or horseradish peroxidase (HRP) was administered intraperitoneally or intravenously to determine vascular permeability. The mRNA and protein expression of HIF-1alpha, VEGF, eNOS, nNOS, and iNOS, along with VEGF concentration and NO production, were increased in response to hypoxia. Swollen Müller cell processes, apoptotic and necrotic cells in the inner nuclear layer, and changes in ganglion cells such as swollen and disrupted mitochondria were observed in hypoxic animals. Increased leakage of RhIC and HRP from retinal and hyaloid vessels was seen after hypoxic exposure. The authors suggest that increased VEGF and NO production in hypoxia resulted in increased vascular permeability, leading to changes in Müller cells and degeneration of neural cells. Melatonin administration reduced VEGF and NO production, diminished leakage of RhIC and HRP, and promoted cell proliferation, suggesting this as a potential therapeutic agent in reducing hypoxia-associated damage in the developing retina.
Publisher: Wiley
Date: 07-02-2014
DOI: 10.1111/CEO.12287
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 25-11-2014
Abstract: To determine the validity, reliability, and measurement characteristics using factor and Rasch analysis of the Very Low Vision Instrumental Activities of Daily Living (IADL-VLV) in persons with severe vision loss. From an initial pool of 296 tasks, 25 were shortlisted after conducting a Delphi survey with persons designated legally blind. Using further input from occupational therapy and low-vision professionals, 11 activities were chosen to be pilot tested. Forty legally blind participants (better eye visual acuity < 20/200) underwent clinical assessments and functional tests as well as the 53 IADL tasks related to the 11 activities. The task pool was refined and condensed using factor and Rasch analysis. Based on iterative principal component analyses, tasks were grouped together into the following domains: reading signs/information access, signature placement, clothes sorting, shelf search, gesture recognition, clock reading, and table search. A final selection of 23 tasks yielded satisfactory measurement characteristics, differentiated between at least four different levels of IADL performance (person separation of 3.8), and had adequate task difficulty for the tested s le (person mean -0.61). In multivariate analyses, only visual acuity (VA) and percent of remaining visual field (VF) were associated with IADL performance. Using a large item pool, participant, and expert input, as well as factor and Rasch analysis, we designed a valid and reliable assessment to measure vision-related IADL performance in persons with severe vision loss. This assessment tool can be used in clinical sight restoration trials.
Publisher: Elsevier BV
Date: 06-2013
Publisher: Future Medicine Ltd
Date: 08-2014
Publisher: WORLD SCIENTIFIC
Date: 04-2010
Publisher: Springer Science and Business Media LLC
Date: 2003
Abstract: A 35-year-old woman who reported persistent significant vision loss for 3 years after taking the antidepressant nefazodone was referred for electrophysiological assessment of vision. The vision changes included reduced acuities, reduced colour vision and visual field constriction in both eyes and were thought to be associated with the use of nefazodone for 6 - 8 weeks, 3 years earlier. Multifocal electroretinograms and visual evoked potentials were recorded using the Visual Evoked Response Imaging System (VERIS) to investigate the nature and site of the neural deficit. The summed retinal response showed a normal a- and b-wave latency and litude, however, the retinal topographic mfERGs showed a severe depression of the macular response in both eyes. The cortical topographic multifocal VEP mapping also showed a central depression in the right eye compared with the left. Two-frame motion and pattern custom mfVEP were also measured to assess different forms of cortical processing and especially of motion as nefazodone has previously been associated with image persistence with moving stimuli. The responses to two frame-motion showed signs of abnormality. Thus these results suggest that the primary locus of neural damage is retinal and is likely to have resulted from neurotoxicity. Other competing hypotheses such as hysterical blindness must be ruled out.
Publisher: Wiley
Date: 11-02-2016
DOI: 10.1111/CEO.12685
Abstract: Emergence of the high-resolution optical coherence tomography has allowed better delineation of retinal layers, and many of the anatomical correlations of these layers have now been agreed upon. However, some anatomical correlates still remain contentious, such as the second hyper-reflective band, which is now termed ellipsoid zone. Despite the lack of consensus of the actual origin of the ellipsoid zone, there has been much interest in evaluating its integrity and intensity in different disease processes. This review paper aims to provide an overview of the ellipsoid zone and its clinical and research applications.
Publisher: Public Library of Science (PLoS)
Date: 22-05-2014
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.OPHTHA.2018.09.015
Abstract: There is an urgent need for a more effective intervention to slow or prevent progression of age-related macular degeneration (AMD) from its early stages to vision-threatening late complications. Subthreshold nanosecond laser (SNL) treatment has shown promise in preclinical studies and a pilot study in intermediate AMD (iAMD) as a potential treatment. We aimed to evaluate the safety of SNL treatment in iAMD and its efficacy for slowing progression to late AMD. The Laser Intervention in Early Stages of Age-Related Macular Degeneration (LEAD) study is a 36-month, multicenter, randomized, sham-controlled trial. Two hundred ninety-two participants with bilateral large drusen and without OCT signs of atrophy. Participants were assigned randomly to receive Retinal Rejuvenation Therapy (2RT The primary efficacy outcome was the time to development of late AMD defined by multimodal imaging (MMI). Safety was assessed by adverse events. Overall, progression to late AMD was not slowed significantly with SNL treatment compared with sham treatment (adjusted hazard ratio [HR], 0.61 95% confidence interval [CI], 0.33-1.14 P = 0.122). However, a post hoc analysis showed evidence of effect modification based on the coexistence of reticular pseudodrusen (RPD adjusted interaction P = 0.002), where progression was slowed for the 222 participants (76.0%) without coexistent RPD at baseline (adjusted HR, 0.23 95% CI, 0.09-0.59 P = 0.002), whereas an increased progression rate (adjusted HR, 2.56 95% CI, 0.80-8.18 P = 0.112) was observed for the 70 participants (24.0%) with RPD with SNL treatment. Differences between the groups in serious adverse events were not significant. In participants with iAMD without MMI-detected signs of late AMD, no significant difference in the overall progression rate to late AMD between those receiving SNL and sham treatment were observed. However, SNL treatment may have a role in slowing progression for those without coexistent RPD and may be inappropriate in those with RPD, warranting caution when considering treatment in clinical phenotypes with RPD. Our findings provide compelling evidence for further trials of the 2RT
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 19-09-2012
DOI: 10.1167/IOVS.12-9434
Abstract: The aim of this study was to compare simultaneous stimulation of multiple electrodes to single-electrode stimulation in a retinal prosthesis. A platinum electrode array was implanted into the suprachoroidal space in six normally sighted anesthetized cats. Multiunit activity from the primary visual cortex in response to retinal stimulation was recorded. Cortical thresholds, yield of responses, dynamic ranges, and the spread of retinal activation were measured for three modes of stimulation: single electrode, half-row (six-electrode horizontal line), and column (seven-electrode vertical line). Stimulation of the best half-rows and columns was found to elicit activity with higher yield and lower charge thresholds per electrode compared to the best single electrodes. Dynamic ranges between the three modes were similar. As expected, peak voltages measured for columns and half-rows were lower than those measured for single electrodes. Spread of retinal activation, determined by the increase in threshold with distance in the retina from the best site, was found to be similar between single- and multiple-electrode stimulation but dependent on orientation. The lower thresholds, higher yield, equivalent dynamic ranges, and equivalent spread of retinal activation observed from simultaneous stimulation of multiple electrodes may be due to current and/or neural summation within the retina. Such stimulation techniques could be useful for the presentation of lines and edges of objects using a suprachoroidal retinal stimulator with low voltage compliance. Furthermore, the results suggest that more complex visual processing strategies in addition to sequential stimulation of in idual electrodes should be considered for retinal prostheses.
Publisher: Elsevier BV
Date: 06-2014
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-11-2013
Abstract: To determine the intrasession test-retest variability of microperimetry in participants with age-related macular degeneration (AMD). This study consisted of two separate groups of subjects who had not performed microperimetry previously. In group 1, 30 AMD and 14 control participants performed three microperimetry examinations of a selected eye within one session (test 1 and 2, first pair test 2 and 3, second pair). Follow-up examination at 6 months was available in 20 AMD participants in group 1, who performed two microperimetry examinations. In group 2, 71 AMD participants performed a short practice examination, then two microperimetry examinations of the right eye (test 1 and 2, first pair) and two of the left eye (test 3 and 4, second pair). There was a significant improvement in average point-wise sensitivity (PWS) between the first pair of examination in both groups (P < 0.001), but not in the subsequent pair (P ≥ 0.774). This improvement was not observed at the follow-up visit in the subset of AMD participants in group 1 (P = 0.433). The PWS coefficient of repeatability (CoR) for the second pair of examinations was ± 4.12 dB and ± 4.37 dB for AMD participants for group 1 and 2 respectively. A significant increase in sensitivity between the first and second test, but not in the subsequent tests, was found for participants who had not performed microperimetry previously. Intrasession test-retest variability can therefore be minimized by discarding the first examination to avoid the influence of a learning effect.
Publisher: IOP Publishing
Date: 18-05-2012
DOI: 10.1088/1741-2560/9/3/036009
Abstract: A clinically effective retinal prosthesis must evoke localized phosphenes in a retinotopic manner in response to stimulation of each of the retinal electrodes, evoke brightness cues over a wide dynamic range and function within safe stimulus limits. The effects of varying return configuration for retinal stimulation are currently unknown. To investigate this, we implanted a flexible, 7 × 12 electrode array into the suprachoroidal space of normally-sighted, anesthetized cats. Multi-unit activity in the primary visual cortex was recorded in response to electrical stimulation using various return configurations: monopolar vitreous (MPV), common ground (CG), hexagonal (HX), monopolar remote (MPR) and bipolar (BP_N). MPV stimulation was found to be the most charge efficient and was most likely to induce cortical activity within safe charge limits. HX and CG stimulation were found to exhibit greater retinal selectivity compared to the MPV return at the expense of lower cortical yield and higher P50 charge levels, while cortical selectivity was unaffected by choice of return. Responses using MPR and widely spaced BP_N configurations were similar to those using the MPV return. These results suggest that choice of return configuration for a retinal prosthesis will be balanced between resolution and stimulation within safe charge limits.
Publisher: Springer Science and Business Media LLC
Date: 11-12-2019
DOI: 10.1038/S41598-019-55315-3
Abstract: Neuroglobin is an endogenous neuroprotective protein. We determined the safety of direct delivery of Neuroglobin in the rat retina and its effects on retinal inflammatory chemokines and microglial during transient hypoxia. Exogenous Neuroglobin protein was delivered to one eye and a sham injection to the contralateral eye of six rats intravitreally. Fundus photography, Optical Coherence Topography, electroretinogram, histology and Neuroglobin, chemokines level were determined on days 7 and 30. Another 12 rats were subjected to transient hypoxia to assess the effect of Neuroglobin in hypoxia exposed retina by immunohistochemistry, retinal Neuroglobin concentration and inflammatory chemokines. Intravitreal injection of Neuroglobin did not incite morphology or functional changes in the retina. Retinal Neuroglobin protein was reduced by 30% at day 7 post hypoxia. It was restored to normoxic control levels with intravitreal exogenous Neuroglobin injections and sustained up to 30 days. IL-6, TNFα, IL-1B, RANTES, MCP-1 and VEGF were significantly decreased in Neuroglobin treated hypoxic retinae compared to non-treated hypoxic controls. This was associated with decreased microglial activation in the retina. Our findings provide proof of concept suggesting intravitreal Neuroglobin injection is non-toxic to the retina and can achieve the functional level to abrogate microglial and inflammatory chemokines responses during transient hypoxia.
Publisher: WORLD SCIENTIFIC
Date: 04-2010
Publisher: Wiley
Date: 04-08-2020
DOI: 10.1111/CEO.13823
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-10-2016
Abstract: Retinal prostheses have emerged as a promising technology to restore vision in patients with severe photoreceptor degeneration. To better understand how neural degeneration affects the efficacy of electronic implants, we investigated the function of a suprachoroidal retinal implant in a feline model. Unilateral retinal degeneration was induced in four adult felines by intravitreal injection of adenosine triphosphate (ATP). Twelve weeks post injection, animals received suprachoroidal electrode array implants in each eye, and responses to electrical stimulation were obtained using multiunit recordings from the visual cortex. Histologic measurements of neural and glial changes in the retina at the implant site were correlated with cortical thresholds from in idual stimulating electrodes. Adenosine triphosphate-injected eyes displayed changes consistent with mid-to-late stage retinal degeneration and remodeling. A significant increase in electrical charge was required to induce a cortical response from stimulation of the degenerated retina compared to that in the fellow control eye. Spatial and temporal characteristics of the electrically evoked cortical responses were no different between eyes. In idual electrode thresholds varied in both the control and the ATP-injected eyes and were correlated with ganglion cell density. In ATP-injected eyes, cortical threshold was also independently correlated with an increase in the extent of retinal gliosis. These data suggest that even when ganglion cell density remains unaffected, glial changes in the retina following degeneration can influence the efficacy of suprachoroidal electrical stimulation. A better understanding of how glial change impacts retinal prosthesis function may help to further the optimization of retinal implants.
Publisher: Springer Science and Business Media LLC
Date: 11-09-2010
DOI: 10.1038/EYE.2009.173
Abstract: To investigate the possible roles of retinal photoreceptors in macular oedema and retinal angiogenesis with particular reference to the mode of action of laser therapy. (i) Studies in rats made hypoxic for 2 h by administering an oxygen/nitrogen mixture of reduced oxygen content, and growth factors determined by RT-PCR, western blotting, and immunohistochemistry. Assessment of blood-retinal barrier integrity using fluorescent and electron-dense tracers. (ii) Studies in pigs with one retina made hypoxic by selective embolisation of the retinal capillary circulation with fluorescent microspheres. (iii) Assessment of laser therapy in selected cases of retinal neovascularisation indicating a role for photoreceptors. In the hypoxic retina, angiogenic and vascular permeability factors such as vascular endothelial growth factor (VEGF), nitric oxide synthases (NOSs), and insulin-like growth factor-1 are upregulated in retinal astrocytes and Müller cells but are also present in large amount in the photoreceptors. Hypoxia-inducible factor-1 (HIF-1) is upregulated in retinal glial cells but not in the photoreceptors, suggesting that growth factors in the photoreceptors may not have been generated there. The tracer dye, rhodium isothiocyanate, leaking from an abnormally permeable inner blood-retinal barrier in the hypoxic retina accumulates in the photoreceptors. The results indicate that laser treatment of macular oedema or retinal neovascularisation may obtain its effect not only by improving oxygen availability in the inner retina, but also by reducing the load of angiogenic ermeability factors that accumulate in the photoreceptors in hypoxic/ischaemic conditions.
Publisher: Wiley
Date: 07-2009
DOI: 10.1111/J.1442-9071.2009.02062.X
Abstract: To investigate the outer and inner retinal function in patients with multiple evanescent white dot syndrome (MEWDS). The retinal function of three subjects with MEWDS was investigated using one or a combination of full-field electroretinography (ERG), multifocal electroretinography (mfERG) or recording of multifocal oscillatory potentials (mfOP). In case 1, the scotopic, maximal, photopic and flicker ERG responses of the two eyes were similar but the litudes of the dark- and light-adapted OPs were markedly reduced in the affected eye. In cases 2 and 3, the ERG responses were grossly reduced in litude and as expected the OPs were also diminished. However, using the mfERG a residual area of 'normal' retinal function in the affected eye was identified. The local OP, assessed by the mfOP, within the residual 'normal' retinal area was reduced as compared with the corresponding retinal area of the fellow unaffected eye. Subsequently, the mfERG responses of the 'normal' retinal area were also reduced. The OPs were reduced throughout the retina in patients with MEWDS, even in the area with a normal mfERG. The electrophysiological findings suggest that functional abnormality in MEWDS may occur initially in the inner retina and subsequently involves the outer retina.
Publisher: Informa UK Limited
Date: 2003
DOI: 10.1076/STRA.11.2.109.15105
Abstract: It is generally agreed that vertical prism bar training can increase vertical fusion litude. However, little is known as to whether the increased vertical fusion litude following vergence exercise is due to improvement of the sensory or the motor system or both. The main aim of the present study was to determine the effect of vertical prism bar training on the motor and sensory components of vertical fusion. Fifty normal subjects between 17 and 25 years of age were given vertical prism bar training to improve their vertical fusion litude. Vertical vergence eye movements were recorded using an infrared reflectance eye tracker system. The sensory component was assessed using a Sheedy disparometer. The findings of the present study showed that the average increase in vertical motor fusion was approximately 30% following vertical prism bar training. The maximum magnitude of VFD remained unchanged in the majority (73%) of subjects. The increase in the vertical fusion litude following vertical prism bar training is largely due to improvements in the vertical motor fusion. The prism training has little effect on the sensory component.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 27-09-2011
DOI: 10.1167/IOVS.11-7912
Abstract: To investigate the effect of tumor necrosis factor alpha (TNF-α) on the mouse retinal vasculature, function, and expression of vascular endothelial growth factor-A (VEGF-A) in the retina and retinal pigment epithelium (RPE) and to evaluate the protective effect of statin therapy (fluvastatin) on retinal vascular and functional changes. A single intravenous injection of murine TNF-α (8 μg/kg body weight) was administered to one group of mice (TNF group). In the second group of mice (TNF+Statin group), a single dose of TNF-α was followed by 28 days oral medication of fluvastatin (10 mg/kg/d), and an equivalent volume of saline was administered to the third group (Control group). After 28 days, electroretinography (ERG) and fundus photography were performed. Eyes were collected for cell and molecular studies. Transcript levels of VEGF-A in retina and RPE were quantified using real-time polymerase chain reaction, and protein expression was analyzed by Western blot and immunostaining. TNF-α-injected mice showed retinal vessel tortuosity, structural change, and altered retinal function. Fluvastatin-treated mice exhibited retinal vascular, structural, and functional changes almost similar to those of the control group. VEGF-A expression was significantly upregulated in the retina and RPE of TNF-α-injected mice, and this was significantly downregulated in fluvastatin-treated mice. This study shows that the TNF-α-induced inflammatory process results in the alteration of retinal microvasculature and function, and fluvastatin could be a potential therapy for treating reventing retinal microvascular or inflammatory complications.
Publisher: Wiley
Date: 27-06-2013
DOI: 10.1111/AOS.12173
Abstract: To determine the reliability and reproducibility of the Vesselmap Oximetry Module for arteriolar and venular oxygen saturation (SO2 ) of the same retinal area, specified by a peripapillary annulus, in healthy subjects. Fundus oximetry images were obtained, using a standardized protocol by a single observer, from the right eye of 20 healthy in iduals. Age range was 19-45 years old, and images were analysed using the oximetry module of the Vesselmap System (Imedos, UG, Germany). Intra-observer reliability (assessment of two measurements of SO2 values performed 5 days apart) interobserver reliability (assessment of SO2 performed by two different trained observers) and intrasubject reproducibility (comparison of SO2 measurements of two different images of the same subject and retinal area, taken 10 min apart) were assessed. The standard deviations between the repeated measurements (SDr), together with the intraclass correlation coefficient (ICC), of these three parameters were calculated. The SDr for intra-observer reliability was 0.56% and 0.55% for arteriolar and venular SO2 , respectively. The results were similar for intrasubject reproducibility (0.69% and 0.79% for arteriolar and venular SO2, respectively) interobserver reliability, however, was higher (SDr 1.22% and 1.01% for arteriolar and venular SO2 , respectively). The ICC values for intra-observer reliability were 0.99 for both arteriolar and venular SO2 . The results were similar for both interobserver reliability (0.94 for arteriolar SO2 and 0.96 for venular SO2 ) and intrasubject reproducibility (0.98 for both arteriolar and venular SO2 ). Retinal oxygen saturation values taken using the oximetry module of the Vesselmap System are highly reliable and reproducible, provided the image quality is standardized, the same measurement area is analysed in each image, and the number of observers analysing the images is kept to a minimum.
Publisher: Wiley
Date: 29-09-2015
DOI: 10.1111/AOR.12582
Abstract: Successful visual prostheses require stable, long-term attachment. Epiretinal prostheses, in particular, require attachment methods to fix the prosthesis onto the retina. The most common method is fixation with a retinal tack however, tacks cause retinal trauma, and surgical proficiency is important to ensure optimal placement of the prosthesis near the macula. Accordingly, alternate attachment methods are required. In this study, we detail a novel method of magnetic attachment for an epiretinal prosthesis using two prostheses components positioned on opposing sides of the retina. The magnetic attachment technique was piloted in a feline animal model (chronic, nonrecovery implantation). We also detail a new method to reliably control the magnet coupling force using heat. It was found that the force exerted upon the tissue that separates the two components could be minimized as the measured force is proportionately smaller at the working distance. We thus detail, for the first time, a surgical method using customized magnets to position and affix an epiretinal prosthesis on the retina. The position of the epiretinal prosthesis is reliable, and its location on the retina is accurately controlled by the placement of a secondary magnet in the suprachoroidal location. The electrode position above the retina is less than 50 microns at the center of the device, although there were pressure points seen at the two edges due to curvature misalignment. The degree of retinal compression found in this study was unacceptably high nevertheless, the normal structure of the retina remained intact under the electrodes.
Publisher: Future Medicine Ltd
Date: 08-2014
Publisher: Elsevier BV
Date: 07-2004
Publisher: Public Library of Science (PLoS)
Date: 06-09-2016
Publisher: Elsevier BV
Date: 04-2013
DOI: 10.1016/J.EXER.2013.01.004
Abstract: Hypoxia-induced glutamate accumulation in neural tissues results in damage to neurons through excitotoxic mechanisms via activation of glutamate receptors (GluRs). Here we examine whether hypoxia in the developing retina would cause activation of the ionotropic α-amino-3-hydroxy-5-methylisoxazole-4-propioate (AMPA) GluRs and increase in Ca(2+) influx into retinal ganglion cells (RGCs) that might ultimately lead to their death. Neonatal Wistar rats were subjected to hypoxia for 2h and then sacrificed at various time points after the exposure together with normal age matched control rats. Primary cultures of RGCs were also prepared and subjected to hypoxia. Expression of AMPA glutamate receptor (GluR) 1-4 was examined in the retina. Additionally, expression of GluRs, intracellular Ca(2+) influx, reactive oxygen species (ROS) generation and cell death were investigated in cultured RGCs. GluR1-4 mRNA and protein expression showed a significant increase (P < 0.01) over control values after the hypoxic exposure both in vivo and in vitro. Cells expressing GluR1-4 in the retina were identified as RGCs by double immunofluorescence labeling with Thy1.1. Increased intracellular Ca(2+) in cultured RGCs following hypoxic exposure was reduced (P < 0.01) by 10 μM AMPA antagonist 6, 7-dinitroquinoxaline-2,3-dione (DNQX). Our results suggest that following a hypoxic insult, an increased amount of glutamate accumulates in the neonatal retina. This would then activate AMPA receptors which may damage RGCs through increased Ca(2+) accumulation and ROS generation. The involvement of AMPA receptors in damaging the RGCs is evidenced by suppression of intracellular Ca(2+) influx by DNQX which also decreased ROS generation and cell death by 50%.
Publisher: Springer Science and Business Media LLC
Date: 10-11-2011
DOI: 10.1038/GT.2011.169
Abstract: We report on the long-term safety of AAV2.sFlt-1 (a recombinant adeno-associated virus serotype 2 carrying the soluble form of the Flt-1 receptor) injection into the subretinal space of non-human primates. Levels of sFlt-1 protein were significantly higher (P<0.05) in the vitreous of four out of five AAV2.sFlt-1-injected eyes. There was no evidence of damage to the eyes of animals that received subretinal injections of AAV2.sFlt-1 ocular examination showed no anterior chamber flare, normal fundus and electroretinography responses equivalent to those observed before treatment. Notably, immunological analysis demonstrated that gene therapy involving subretinal injection of AAV2.sFlt-1 does not elicit cell-mediated immunity. Biodistribution analysis showed that AAV2.sFlt-1 could be detected only in the eye and not in the other organs tested. These data indicate that gene therapy with subretinal AAV2.sFlt-1 is safe and well tolerated, and therefore promising for the long-term treatment of neovascular diseases of the eye.
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.OPHTHA.2014.06.034
Abstract: To characterize the pathological changes preceding the development of drusen-associated atrophy in eyes with age-related macular degeneration (AMD) using spectral-domain optical coherence tomography (SD-OCT). Longitudinal and cross-sectional retrospective observational study. A total of 181 participants with intermediate AMD in at least 1 eye (141 unilateral, 40 bilateral) were assessed longitudinally. A total of 230 participants with bilateral intermediate AMD (40 longitudinal participants with an additional 190 participants) were analyzed cross-sectionally. Spectral-domain OCT, color fundus photography (CFP), near-infrared reflectance, and fundus autofluorescence imaging were performed in all participants at cross-section and every 3 months for up to 30 months in the longitudinal study. Spectral-domain OCT volume scans were examined for features that portend the development of drusen-associated atrophy, and the topography, prevalence, and risk factors of these features were determined through cross-sectional analysis. The pathological features on SD-OCT preceding the development of drusen-associated atrophy and the characteristics of these features. Twenty areas from 16 eyes of 16 participants developed drusen-associated atrophy after an average of 20 months (range, 8-30 months). Spectral-domain OCT features unique in these areas included: subsidence of the outer plexiform layer (OPL) and inner nuclear layer (INL), and development of a hyporeflective wedge-shaped band within the limits of the OPL. These characteristics were termed "nascent geographic atrophy" (nGA), describing features that portend the development of drusen-associated atrophy. Cross-sectional examination of participants with bilateral intermediate AMD revealed that independent risk factors for the presence of nGA included the presence of pigmentary changes (odds ratio [OR], 16.84 95% confidence interval [CI], 2.42-117.24) and nGA in the fellow eye (OR, 4.15 95% CI, 1.12-15.34) nGA was present in 21.9% of participants with drusen >125 μm and pigmentary changes in both eyes. This study identified pathological changes occurring before the development of drusen-associated atrophy using SD-OCT, which we defined as nGA. Although nGA is undetectable on CFP, it is important for determining the risk of future vision loss in AMD and could be used as an earlier surrogate end point in interventional trials targeting the early stages of AMD.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 23-01-2014
Abstract: To determine the effect of a statin (simvastatin) on the ultrastructure and function of the RPE, Bruch's membrane (BM), and photoreceptor interface in a high-fat atherogenic mouse model of thickened BM. Wild-type C57BL/6 mice (6-weeks old) were ided into three study groups according to their diet and treatment given Group 1, normal chow diet-fed mice Group 2, high fat diet (HFD) fed mice and Group 3, HFD-fed mice treated with simvastatin daily for 30 weeks. All mice were followed-up for 30 weeks. The retinal morphology and function was examined in vivo using fundus imaging and electroretinography at 15- and 30-weeks follow-up. At the end of the study, at 36 weeks of age, eye tissues were collected and retinal sections were examined using light microscopy and transmission electron microscopy. Fundus images of the HFD-fed mice showed the presence of discrete, multiple white spots, which was significantly reduced by approximately 73% in the simvastatin-treated animals. In the HFD-fed mice, there was an increase in the empty cytoplasmic vacuoles of the RPE, presence of lipid droplets in the BM, thickening and fragmentation of the elastic lamina of the BM, and a reduction in retinal function these ultrastructural and functional changes were significantly improved in the simvastatin-treated group. Chronic administration of simvastatin significantly improves the ultrastructure and function of the RPE, BM, and photoreceptor in a high-fat atherogenic mouse model of thickened BM.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 14-07-2016
Abstract: To determine whether longitudinal changes in mesopic visual function on microperimetry occurred independent of its associations with microstructural parameters on spectral-domain optical coherence tomography (SD-OCT) in the early stages of AMD. Forty-one AMD eyes underwent microperimetry testing and SD-OCT scans over a 12-month period at 6-month intervals. Microstructural parameters analyzed include the retinal pigment epithelium-drusen complex (RPEDC) layer thickness, number of hyperreflective foci (HF) and their inner retinal migration (represented by a weighted axial distribution score AxD), and the number of atrophic areas. Microperimetric sensitivity was 0.29 dB (95% confidence interval [CI] = -0.38 to -0.20 dB, P < 0.001) and 0.13 dB (95% CI = -0.22 to -0.03 dB, P = 0.008) lower in each sector for every 10-μm higher RPEDC layer thickness and 1-HF present, but was not associated with the AxD score or the number of atrophic areas present (P ≤ 0.464). However, each 10-μm greater RPEDC layer thickness and 1-HF present was not independently associated with a further decline in sensitivity (-0.08 dB/year, 95% CI = -0.24 to 0.07 dB/year, P = 0.288 and 0.09 dB/year, 95% CI = -0.06 to 0.24 dB/year, P = 0.242, respectively) over time when accounting for the association between RPEDC layer thickness and number of HF with microperimetric sensitivity. Longitudinal changes in mesopic visual function measured on microperimetry paralleled changes in the microstructural changes over a 12-month time frame, without any changes occurring independent of the associations between structure and function alone.
Publisher: IOP Publishing
Date: 26-06-2014
DOI: 10.1088/1741-2560/11/4/046017
Abstract: The research goal is to develop a wide-field retinal stimulating array for prosthetic vision. This study aimed at evaluating the efficacy of a suprachoroidal electrode array in evoking visual cortex activity after long term implantation. A planar silicone based electrode array (8 mm × 19 mm) was implanted into the suprachoroidal space in cats (ntotal = 10). It consisted of 20 platinum stimulating electrodes (600 μm diameter) and a trans-scleral cable terminated in a subcutaneous connector. Three months after implantation (nchronic = 6), or immediately after implantation (nacute = 4), an electrophysiological study was performed. Electrode total impedance was measured from voltage transients using 500 μs, 1 mA pulses. Electrically evoked potentials (EEPs) and multi-unit activity were recorded from the visual cortex in response to monopolar retinal stimulation. Dynamic range and cortical activation spread were calculated from the multi-unit recordings. The mean electrode total impedance in vivo following 3 months was 12.5 ± 0.3 kΩ. EEPs were recorded for 98% of the electrodes. The median evoked potential threshold was 150 nC (charge density 53 μC cm(-2)). The lowest stimulation thresholds were found proximal to the area centralis. Mean thresholds from multiunit activity were lower for chronic (181 ± 14 nC) compared to acute (322 ± 20 nC) electrodes (P < 0.001), but there was no difference in dynamic range or cortical activation spread. Suprachoroidal stimulation threshold was lower in chronic than acute implantation and was within safe charge limits for platinum. Electrode-tissue impedance following chronic implantation was higher, indicating the need for sufficient compliance voltage (e.g. 12.8 V for mean impedance, threshold and dynamic range). The wide-field suprachoroidal array reliably activated the retina after chronic implantation.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-02-2015
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 31-03-2015
Abstract: To examine the influence of reticular pseudodrusen (RPD) on retinal and visual function in intermediate AMD using multifocal electroretinography (mfERG) and microperimetry. In a prospective cross-sectional study, microperimetry and mfERG testing, followed by color fundus photography, near-infrared reflectance imaging and spectral-domain optical coherence tomography (SD-OCT) scans were performed in 120 eyes from 60 participants with bilateral intermediate AMD. The number of subfields with pigmentary changes and RPD within the central 3-mm diameter of the Early Treatment of Diabetic Retinopathy Study (ETDRS) grid and drusen cube root volume within the central 3-mm diameter was determined. The influence of these pathological features on microperimetry and mfERG in this region were examined. Microperimetric sensitivity was not significantly associated with the presence and extent of RPD (P = 0.068), but with drusen volume and extent of pigmentary changes (P < 0.001 for both). However, the presence and extent of RPD was independently and significantly associated with mfERG implicit time, along with drusen volume and the extent of pigmentary changes (P ≤ 0.023). The mfERG response litude was not significantly associated with the presence and extent of RPD (P = 0.130). The presence and extent of RPD was associated with functional changes on mfERG implicit time, but not mfERG response litude or microperimetry. These findings suggest that the presence of RPD in eyes with intermediate AMD has a significant influence on cone-mediated neuroretinal function, without a significant influence on mesopic visual function as determined on microperimetry.
Publisher: Springer Science and Business Media LLC
Date: 03-2005
DOI: 10.1007/S10633-005-3742-4
Abstract: Retinopathy of prematurity (ROP) is often associated with myopia. Electrophysiological findings have shown that an imbalance of the ON- and OFF-response in subjects with ROP is associated with their refractive status. Nevertheless, the extent of these functional changes is still unclear. The aim of this study was to determine the extent of the ON- and OFF-response attenuation in ROP subjects with myopia. Fast and slow m-sequence multifocal electroretinogram were recorded on 14 eyes in 8 subjects with various degrees of myopia using the VERIS system. The spherical equivalent of refractive error ranged from -0.25 to -13.50 D. All ERG recordings were made using DTL electrodes with dilated pupils. A 19 retinally scaled hexagon stimulus was used. The findings showed that the ON- and OFF-response are reduced differently in ROP subjects with myopia. The ON-response attenuation is dependant on the severity of myopia, whereas, the OFF-response attenuation is influenced by retinal eccentricity as well as the degree of myopia. The contributions of these findings toward the understanding of retinal mechanisms controlling ocular growth need to be further explored.
Publisher: Informa UK Limited
Date: 05-2016
DOI: 10.2147/EB.S70822
Publisher: Oxford University Press (OUP)
Date: 04-2012
Publisher: American Medical Association (AMA)
Date: 06-2012
DOI: 10.1001/ARCHOPHTHALMOL.2012.277
Abstract: To investigate the longitudinal changes in flicker perimetry in patients with age-related macular degeneration (AMD) as the condition progresses from early AMD to geographic atrophy (GA) or choroidal neovascularization (CNV). Patients with AMD and control subjects were recruited from a longitudinal study of retinal function in early AMD consisting of 187 participants. Only those who completed at least 4 consecutive, 6-monthly flicker perimetry tests were selected for this study. Study groups consisted of everyone who went on to develop GA (n = 16) or CNV (n = 5), controls (n = 24), and the high-risk, early- AMD participants whose eyes did not progress to GA or CNV (drusen >125 μm n = 18). The flicker sensitivity was determined, and its rate of change during the 18 months before the clinical detection of late AMD was calculated. Eyes that went on to develop GA or CNV had a significantly reduced mean (SD) flicker sensitivity in the months before clinical detection of GA (15.8 [5.6] dB) or CNV (19.1 [3.8] dB) compared with control eyes (22.9 [3.0] dB) (P < .001) and with eyes that did not progress to GA or CNV (21.4 [3.4] dB) (P < .001). The rate of change in flicker sensitivity was significantly increased in GA eyes (-0.07 dB/mo) (P < .001) but not in CNV eyes (0.006 dB/mo) (P = .56) compared with the control eyes (-0.003 dB/mo). Flicker sensitivity is reduced in eyes that go on to develop late AMD. The rate of change in flicker sensitivities over time was particularly useful in predicting eyes and areas within the eye that subsequently develop GA.
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1016/J.OPHTHA.2014.01.025
Abstract: To determine the relationship between structural parameters of the outer retina on spectral-domain optical coherence tomography (SD-OCT) and microperimetric retinal sensitivity in early stages of age-related macular degeneration (AMD). Prospective, observational study. Seventy-five eyes of 75 participants with early stages of AMD (drusen ≥ 125 μm, with/without pigmentary abnormalities) and 25 control participants of a similar age. Participants underwent microperimetry testing and high-resolution SD-OCT scans. Structural parameters at 5 central points (0°, 1°, and 2.33° nasal and temporal to the fovea along the horizontal axis) corresponding to areas tested by microperimetry were compared. Structural parameters included outer segment (OS) length, thickness and elevation of the retinal pigment epithelium (RPE) band, grading of the inner-segment ellipsoid (ISe) band integrity, and presence of hyperreflective foci (HF). Relationship between structural parameters and retinal sensitivity. Retinal sensitivity was significantly correlated with RPE elevation (P<0.001), ISe grading (P<0.001), and presence of HF (P ≤ 0.018) at all test points, but not with OS length (P ≥ 0.093) or RPE thickness (P ≥ 0.125). However, multiple linear regression analyses revealed that only ISe grading (P ≤ 0.011) and RPE elevation (P ≤ 0.030) remained significantly associated with retinal sensitivity at all points. By using a simple linear model incorporating ISe grading and RPE elevation to predict values of retinal sensitivity, the 95% limits of agreement between the predicted and the actual value was ± 3.83 dB. The integrity of the ISe band and drusen-associated RPE elevation are significant independent predictors of microperimetric retinal sensitivity. Our findings imply that these 2 structural parameters may be surrogate markers of retinal function in the early stages of AMD.
Publisher: American Medical Association (AMA)
Date: 08-2007
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 30-09-2014
Abstract: The mechanisms supporting the protective relationship between a longer axial length (AL) and a decreased risk of diabetic retinopathy (DR) remain unclear. Previous studies have demonstrated reduced retinal blood flow in axial myopia, and it has been suggested that the compromised retinal capillaries in diabetes are less likely to leak and rupture as a result of this decreased flow. In this study, we therefore investigated if reduced retinal capillary flow (RCF) is a potential mechanism underpinning this protective relationship. Retinal capillary flow was assessed using the Heidelberg Retinal Flowmeter in 150 eyes of 85 patients with diabetes aged 18+ years from the Royal Victorian Eye and Ear Hospital and St. Vincent's Hospital (Melbourne), Australia. Axial length was measured using the Intraocular Lens Master. Diabetic retinopathy was graded from two-field retinal photographs into none, mild, moderate, and severe DR using the modified Airlie House classification system. A total of 74 out of 150 eyes (49.3%) had DR. A longer AL was associated with decreased odds of DR presence (per mm increase in AL, odds ratio [OR] 0.61, 95% confidence interval [CI] 0.41-0.91) and DR severity (OR: 0.65 95% CI: 0.44-0.95). However, no association was found between AL and RCF (per mm increase in AL, regression coefficient [β] -1.80, 95% CI -13.50 to 9.50) or between RCF and DR (per unit increase in RCF, OR 1.00 95% CI 0.99-1.00). Our finding suggests that diminished RCF may not be a major factor underlying the protective association between axial elongation and DR.
Publisher: Wiley
Date: 24-10-2022
DOI: 10.1111/CEO.14018
Abstract: Subthreshold nanosecond laser (SNL) treatment has been studied as a potential intervention in intermediate age‐related macular degeneration (iAMD). This study investigated the effect of 100 SNL treatment spots on retinal structure and function. A prospective single‐arm interventional pilot study. SNL treatment was delivered as 100 spots around the retinal vascular arcades of the study eye (worst visual acuity) in a single session in subjects with iAMD. Multimodal retinal imaging and dark‐adapted chromatic perimetry were performed at baseline and at 0.5, 3, 6 and 12 months post treatment. Post treatment changes in best corrected visual acuity (BCVA), retinal thickness, relative ellipsoid zone reflectivity (rEZR) and rod‐mediated functional parameters were compared to baseline. Twenty‐one subjects with iAMD were recruited. SNL treatment was associated with an increase in retinal thickness ( p = 0.008) and decrease in rEZR ( p 0.001) at 2 weeks post laser. Recovery of retinal thickness and rEZR was observed at the 3‐month post laser visit. A gradual improvement in BCVA was observed after laser treatment. The mean change in BCVA between baseline and 12‐month visit was +1.9 ± 3.3 letters for the SNL treated eyes, compared to −0.4 ± 3.0 letters for the fellow eyes ( p = 0.027). Rod‐mediated function improved at 3 months post laser ( p 0.001) and returned to the baseline levels at 12 months post treatment. A single treatment with 100 SNL spots causes a short‐term change in retinal structure and improvement in retinal function that are apparent at 3 months post treatment.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2016
Publisher: Springer Science and Business Media LLC
Date: 05-01-2013
DOI: 10.1007/S10633-012-9372-8
Abstract: The aims of this study were to determine the longitudinal effects of myopia on full-field electroretinogram (ffERG) in children, and whether there were any effects due to atropine treatment. Fifty children, enrolled in the atropine treatment for myopia study, were randomly selected and 35 children consented to undergo ffERG at baseline (prior to atropine treatment), 24 months (at end of treatment) and 32 months (8 months after cessation of treatment). An extended ISCEV ffERG protocol was used for all recordings. The relationship between axial length (AL) and the following scotopic and photopic ffERG responses was analyzed: a- and b-wave litude and implicit time, saturated litude (V max), and retinal sensitivity (logK). Reliable ffERG recordings with acceptable level of noise were obtained on all 3 visits from 29 children (mean age: 9.5 ± 0.8 years and mean spherical equivalent: -5.0 ± 1.6 D). At baseline, the correlation detected between AL and logK was 0.37 (p = 0.047). There was no significant correlation between AL and V max or any scotopic and photopic ffERG litude and implicit time measures. Longitudinal data suggested a reduction in photopic a- and b-wave and 30 Hz flicker response litudes over time. Multivariate analysis showed that the change in 30 Hz flicker response litude was likely to be associated with AL change. There was no evidence that changes in other responses were associated with age, baseline AL, or atropine dose used. Retinal sensitivity was reduced in myopic children. There was a gradual decline in cone function over time which was not influenced by atropine treatment.
Publisher: Wiley
Date: 04-2014
DOI: 10.1111/AOR.12287
Abstract: Retinitis pigmentosa affects over 1.5 million people worldwide and is a leading cause of vision loss and blindness. While retinal prostheses have shown some success in restoring basic levels of vision, only generic, "one-size-fits-all" devices are currently being implanted. In this study, we used optical coherence tomography scans of the degenerated retina from 88 patients with retinitis pigmentosa to generate models of retinal thickness and curvature for the design of customized implants. We found the average retinal thickness at the fovea to be 152.9 ± 61.3 μm, increasing to a maximum retinal thickness of 250.9 ± 57.5 μm at a nasal eccentricity of 5°. These measures could be used to assist the development of custom-made penetrating electrodes to enhance and optimize epiretinal prostheses. From the retinal thickness measurements, we determined that the optimal length of penetrating electrodes to selectively stimulate retinal ganglion cell bodies and interneuron axons in the ganglion cell layer should be 30-100 μm, and to preferentially stimulate interneurons in the inner nuclear layer, electrodes should be 100-200 μm long. Electrodes greater than 200 μm long had the potential to penetrate through the retina into the choroid, which could cause devastating complications to the eye and should be avoided. The two- and three-dimensional models of retinal thickness developed in this study can be used to design patient-specific epiretinal implants that will help with safety and to optimize the efficacy of neuronal stimulation, ensuring the best functional performance of the device for patients.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: Russian Federation
Location: Russian Federation
No related grants have been discovered for Chi Luu.