ORCID Profile
0000-0002-3994-1700
Current Organisations
Flinders University
,
University of Melbourne
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Publisher: Elsevier BV
Date: 07-2006
DOI: 10.1016/J.EXER.2005.10.029
Abstract: P-Glycoprotein (P-gp), an active efflux transporter encoded by the MDR1 gene, has recently been identified in the human and pig retinal pigment epithelium (RPE) in situ. Efflux pumps such as P-gp are major barriers to drug delivery in several tissues. We wished to establish whether human RPE cell lines express P-gp under the culture conditions recommended for each cell line so as to determine their suitability as in vitro models for predicting drug transport across the outer blood-retinal barrier. Three human RPE cell lines, ARPE19, D407 and h1RPE were investigated. Reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out to determine the expression of MDR1 mRNA. Immunocytochemistry using the P-gp-specific antibody C219 was undertaken to investigate the presence of P-gp protein in each cell type. Uptake of rhodamine 123, a P-gp substrate, in the presence or absence of pre-treatment with a P-gp inhibitor, verapamil, was measured in each cell line to determine functional expression of P-gp. For all experiments, MDCK cells stably transfected with the human MDR1 gene (MDCK-MDR1) were used as a positive control. ARPE19 cells were consistently negative for P-gp as assessed by RT-PCR and immunocytochemistry. By contrast, RT-PCR of D407 and h1RPE s les yielded weak bands corresponding to MDR1 P-gp protein expression, as demonstrated by C219 immunoreactivity, was also present. Rhodamine uptake after treatment with verapamil was significantly greater in D407 and MDCK-MDR1, indicating functional expression of P-gp in these two cell lines. No evidence of functional P-gp was found in ARPE19 and h1RPE. In conclusion, D407 and h1RPE cells express P-gp, though functional activity was demonstrable only in D407 cells. ARPE19 cells do not express P-gp. Of these human RPE cells lines D407 could be considered as a suitable model for in vitro drug transport studies, particularly those involving P-gp substrates, without modification of their usual culture conditions.
Publisher: SAGE Publications
Date: 11-2016
Publisher: MDPI AG
Date: 13-04-2023
DOI: 10.20944/PREPRINTS202304.0321.V1
Abstract: Background: The electroretinogram is a clinical test used to assess the function of the photoreceptors and retinal circuits of various cells in the eye, with the recorded waveform being the result of the summated response of neural generators across the retina. Methods: The present investigation involved an analysis of the electroretinogram waveform in both the time and time-frequency domain through the utilization of the discrete wavelet transform and continuous wavelet transform techniques. The primary aim of this study was to monitor and evaluate the effects of treatment in a New Zealand rabbit model of endophthalmitis via electroretinogram waveform analysis. Results: The wavelet scalograms were analyzed using various mother wavelets, including the Daubechies, Ricker, Wavelet Biorthogonal 3.1 (bior3.1), Morlet, Haar, and Gaussian wavelets. Distinctive variances were identified in the wavelet scalograms. Conclusions: The study compared Adult, Child, and Rabbit electroretinogram responses using DWT and CWT, finding that Adult signals had higher power than Child signals, and Rabbit signals showed differences in a-wave and b-wave depending on the type of response tested, while Haar Wavelet was found to be superior in visualizing frequency components in electrophysiological signals.
Publisher: MDPI AG
Date: 19-05-2023
DOI: 10.20944/PREPRINTS202304.0321.V2
Abstract: Background: The electroretinogram is a clinical test used to assess the function of the photoreceptors and retinal circuits of various cells in the eye, with the recorded waveform being the result of the summated response of neural generators across the retina. Methods: The present investigation involved an analysis of the electroretinogram waveform in both the time and time-frequency domain through the utilization of the discrete wavelet transform and continuous wavelet transform techniques. The primary aim of this study was to monitor and evaluate the effects of treatment in a New Zealand rabbit model of endophthalmitis via electroretinogram waveform analysis and to compare these with normal human electroretinograms Results: The wavelet scalograms were analyzed using various mother wavelets, including the Daubechies, Ricker, Wavelet Biorthogonal 3.1 (bior3.1), Morlet, Haar, and Gaussian wavelets. Distinctive variances were identified in the wavelet scalograms between rabbit and human electroretinograms. The wavelet scalograms in the rabbit model of endophthalmitis showed recovery with treatment in parallel with the time -domain features. Conclusions: The study compared Adult, Child, and Rabbit electroretinogram responses using DWT and CWT, finding that Adult signals had higher power than Child signals, and Rabbit signals showed differences in a-wave and b-wave depending on the type of response tested, while Haar Wavelet was found to be superior in visualizing frequency components in electrophysiological signals in following the treatment of endophthalmitis and may give additional outcome measures for the management of retinal disease.
Publisher: SAGE Publications
Date: 08-05-2017
Abstract: The Vygotsky Blocks Test assesses problem-solving styles within a theoretical framework for the development of higher mental processes devised by Vygotsky. Because both the theory and the associated test situate cognitive development within the child’s social and linguistic context, they address conceptual issues around the developmental relation between language and thought that are pertinent to development in autism. Our aim was to document the performance of adults with autism spectrum disorder on the Vygotsky Blocks Test, and our results showed that they made more errors than the typically developing participants and that these errors correlated with performance IQ. The autism spectrum disorder group also required more cues than the typically developing group to discern the conceptual structure of the blocks, a pattern that correlated with Autism Diagnostic Observational Schedule–Communication and Imagination/Creativity sub-scales. When asked to categorize the blocks in new ways, the autism spectrum disorder participants developed fewer principles on which to base new categorizations, which in contrast to the typically developing group correlated with verbal IQ and with the Imagination/Creativity sub-scale of the ADOS. These results are in line with a number of existing findings in the autism spectrum disorder literature and confirm that conceptualization in autism spectrum disorder seems to rely more on non-verbal and less on imaginative processes than in typically developing in iduals. The findings represent first steps to the possibility of outlining a testable account of psychological development in autism spectrum disorder that integrates verbal, non-verbal and social factors into the transition from elementary to higher level processes.
Publisher: Springer Science and Business Media LLC
Date: 06-2018
Publisher: Frontiers Media SA
Date: 06-06-2022
DOI: 10.3389/FNINS.2022.890461
Abstract: To evaluate the electroretinogram waveform in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) using a discrete wavelet transform (DWT) approach. A total of 55 ASD, 15 ADHD and 156 control in iduals took part in this study. Full field light-adapted electroretinograms (ERGs) were recorded using a Troland protocol, accounting for pupil size, with five flash strengths ranging from –0.12 to 1.20 log photopic cd.s.m –2 . A DWT analysis was performed using the Haar wavelet on the waveforms to examine the energy within the time windows of the a- and b-waves and the oscillatory potentials (OPs) which yielded six DWT coefficients related to these parameters. The central frequency bands were from 20–160 Hz relating to the a-wave, b-wave and OPs represented by the coefficients: a20, a40, b20, b40, op80, and op160, respectively. In addition, the b-wave litude and percentage energy contribution of the OPs (%OPs) in the total ERG broadband energy was evaluated. There were significant group differences ( p & 0.001) in the coefficients corresponding to energies in the b-wave (b20, b40) and OPs (op80 and op160) as well as the b-wave litude. Notable differences between the ADHD and control groups were found in the b20 and b40 coefficients. In contrast, the greatest differences between the ASD and control group were found in the op80 and op160 coefficients. The b-wave litude showed both ASD and ADHD significant group differences from the control participants, for flash strengths greater than 0.4 log photopic cd.s.m –2 ( p & 0.001). This methodological approach may provide insights about neuronal activity in studies investigating group differences where retinal signaling may be altered through neurodevelopment or neurodegenerative conditions. However, further work will be required to determine if retinal signal analysis can offer a classification model for neurodevelopmental conditions in which there is a co-occurrence such as ASD and ADHD.
Publisher: Informa UK Limited
Date: 02-01-2020
DOI: 10.1111/CXO.13068
Publisher: Springer Science and Business Media LLC
Date: 29-09-2023
Publisher: Springer Science and Business Media LLC
Date: 07-02-2020
Publisher: Springer Science and Business Media LLC
Date: 28-09-2019
Publisher: IEEE
Date: 11-07-2022
Publisher: Springer Science and Business Media LLC
Date: 06-05-2022
DOI: 10.1186/S11689-022-09440-2
Abstract: Attention Deficit Hyperactivity Disorder (ADHD) is the most prevalent childhood neurodevelopmental disorder. It shares some genetic risk with Autism Spectrum Disorder (ASD), and the conditions often occur together. Both are potentially associated with abnormal glutamate and GABA neurotransmission, which can be modelled by measuring the synaptic activity in the retina with an electroretinogram (ERG). Reduction of retinal responses in ASD has been reported, but little is known about retinal activity in ADHD. In this study, we compared the light-adapted ERGs of in iduals with ADHD, ASD and controls to investigate whether retinal responses differ between these neurodevelopmental conditions. Full field light-adapted ERGs were recorded from 15 ADHD, 57 ASD (without ADHD) and 59 control participants, aged from 5.4 to 27.3 years old. A Troland protocol was used with a random series of nine flash strengths from −0.367 to 1.204 log photopic cd.s.m −2 . The time-to-peak and litude of the a- and b-waves and the parameters of the Photopic Negative Response (PhNR) were compared amongst the three groups of participants, using generalised estimating equations. Statistically significant elevations of the ERG b-wave litudes, PhNR responses and faster timings of the b-wave time-to-peak were found in those with ADHD compared with both the control and ASD groups. The greatest elevation in the b-wave litudes associated with ADHD were observed at 1.204 log phot cd.s.m −2 flash strength ( p .0001), at which the b-wave litude in ASD was significantly lower than that in the controls. Using this measure, ADHD could be distinguished from ASD with an area under the curve of 0.88. The ERG b-wave litude appears to be a distinctive differential feature for both ADHD and ASD, which produced a reversed pattern of b-wave responses. These findings imply imbalances between glutamate and GABA neurotransmission which primarily regulate the b-wave formation. Abnormalities in the b-wave litude could provisionally serve as a biomarker for both neurodevelopmental conditions.
Publisher: Springer Science and Business Media LLC
Date: 23-02-2023
DOI: 10.3758/S13414-023-02670-Z
Abstract: The aim of this report was to analyze reaction times and accuracy in children with a vision impairment performing a feature-based visual search task using a multiverse statistical approach. The search task consisted of set sizes 4, 16, and 24, consisting of distractors (circle) and a target (ellipse) that were presented randomly to school-aged in iduals with or without a vision impairment. Interactions and main effects of key variables relating to reaction times and accuracy were analyzed via a novel statistical method blending GAMLSS (generalized additive models for location, scale, and shape) and distributional regression trees. Reaction times for the target-present and target-absent conditions were significantly slower in the vision impairment group with increasing set sizes ( p .001). Female participants were significantly slower than were males for set sizes 16 and 24 in the target-absent condition ( p .001), with male participants being significantly slower than females in the target-present condition ( p .001). Accuracy was only significantly worse ( p = .03) for participants less than 14 years of age for the target-absent condition with set sizes 16 and 24. There was a positive association between binocular visual acuity and search time ( p .001). The application of GAMLSS with distributional regression trees to the analysis of visual search data may provide further insights into underlying factors affecting search performance in case-control studies where psychological or physical differences may influence visual search outcomes.
Publisher: Springer Science and Business Media LLC
Date: 10-10-2017
DOI: 10.1007/S10633-017-9616-8
Abstract: The aim of the meta-analysis was to derive a range of mean normal clinical electrooculogram (EOG) values from a systematic review of published EOG studies that followed the guidelines of the ISCEV standard for clinical electro-oculography. A systematic literature review was performed using four relevant databases limited to peer-reviewed articles in English between 1967 and February 2017. Studies reporting clinical EOG or FO normal values were included when the report used a standard 30° horizontal saccade, a retinal luminance of between 100 and 250 cd m The mean dilated LP:DT ratio was 2.35 (95% CI 2.28-2.42) undilated LP:DT ratio was 2.37 (95% CI 2.28-2.45) LP litude was 835 (95% CI 631-1039) µV and the mean time to the LP being 8.2 (95% CI 7.7-8.7) min. The mean DT litude was 358 (95% CI 292-424) µV, and the mean FO peak-to-trough ratio was 1.13 (95% CI 1.11-1.16). The results of the LP/DT ratio are drawn from studies with a mean ± standard deviation (SD) age of 34.08 ± 12.93 years for dilated and 33.65 ± 12.28 years for undilated LP/DT ratios. The meta-analysis of EOG studies has generated a reference range of normal mean values for clinicians to refer to when using the ISCEV clinical EOG. It provides a potential method to generate similar data sets from published normal values in related visual electrophysiology tests.
Publisher: Springer Science and Business Media LLC
Date: 05-10-2006
DOI: 10.1007/S10633-006-9023-Z
Abstract: Cystic fibrosis (CF) is caused by a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) which is a chloride channel. CFTR is expressed in the retinal pigment epithelium (RPE) where it is believed to be important in generating the fast oscillations (FOs) and potentially contributing to the light-electro-oculogram (EOG). The role of CFTR in the alcohol-EOG is unknown. We recruited six in iduals with CF (three homozygotes for Delta508 and three heterozygous for Delta508) and recorded the light- and alcohol-EOGs as well as the FOs and compared them to a control group. The results showed that in the CF group the litude of the alcohol- and light-EOGs were normal. However, the time to peak of the light- and alcohol-rises were significantly faster than in the control group. We conclude that CFTR is not primarily responsible for the alcohol- or light-rises but is involved in altering the timing of these responses. The FOs showed differences between the homozygotes, heterozygotes and the controls. The litudes were significantly higher and the time to the dark troughs were significantly slower in the heterozygote group compared to both controls and the homozygotes. In contrast, the homozygotes did not differ in either litude or the timing of the FOs compared to the controls.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2016
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-2004
DOI: 10.1167/IOVS.04-0624
Abstract: To assess the relative resistance presented in idually by Bruch's membrane-choroid (BC) and the retinal pigment epithelium (RPE) to movement of taurine between the choroidal circulation and the outer retina. To quantify the effect of light-evoked changes in subretinal potassium concentration on the transepithelial transport of taurine across bovine RPE. Transport studies were performed in Ussing chambers with intact and RPE-denuded specimens of BC. RPE viability was monitored by recording transepithelial potential (TEP) and transepithelial resistance (TER). Taurine transport with substrate concentrations in the micro- and millimolar range, reflecting physiological taurine concentrations in plasma, retina, and subretinal space was quantified by high-performance liquid chromatography (HPLC) and radiotracer techniques. Taurine transport was also assessed after apical potassium concentration was lowered from 6.0 to 2.2 mM to mimic the effects of light. Transport of taurine across RPE-BC at a 10-mM substrate concentration increased from 32.92 before to 111.72 nanomoles/4 mm per hour after removal of the RPE. Similarly, at 50 microM taurine, transport rates increased from 0.158 to 0.439 nanomoles/4 mm per hour after removal of the RPE. At both high (10 mM) and low (50 microM) substrate concentrations, lowering of apical potassium was associated with decreased transport of taurine across the RPE. For taurine concentrations greater than 42 microM, the rate-limiting compartment for transport of taurine to the outer retina was the RPE monolayer. Similar rates were observed across each compartment for concentrations <42 microM. The magnitude and directionality of taurine transport across the RPE is determined solely by the driving taurine concentration gradient and is modulated by subretinal levels of potassium. Such modulation may provide a mechanism for conserving retinal taurine. Processes that increase the resistance to diffusion across Bruch's membrane such as human ageing and increased thickening and deposition of debris associated with age-related macular degeneration (AMD) are likely to affect transport across the RPE, culminating in a secondary retinal taurine deficiency.
Publisher: Springer Science and Business Media LLC
Date: 21-01-2017
DOI: 10.1007/S10633-017-9573-2
Abstract: The clinical electro-oculogram (EOG) is an electrophysiological test of the outer retina and retinal pigment epithelium (RPE) in which changes in the electrical potential across the RPE are recorded during successive periods of dark and light adaptation. This document presents the 2017 EOG Standard from the International Society for Clinical Electrophysiology of Vision (ISCEV: www.iscev.org ). This standard has been reorganized and updated to include an explanation of the mechanism of the EOG, but without substantive changes to the testing protocol from the previous version published in 2011. It describes methods for recording the EOG in clinical applications and gives detailed guidance on technical requirements, practical issues and reporting of results with the main clinical measure (the Arden ratio) now termed the light peak:dark trough ratio. The standard is intended to promote consistent quality of testing and reporting within and between clinical centers.
Publisher: Wiley
Date: 04-08-2009
DOI: 10.1111/J.1475-1313.2009.00671.X
Abstract: The retinal pigment epithelium is an important barrier to drug transport as well as contributing to the normal functioning of the photoreceptors. The contributions of glial cells in the retina to the maintenance and development of this barrier is important. There is evidence that retinal secreted factors play a role in the induction and maintenance of the outer blood retinal barrier. One possible source of such factors are the retinal glial cells, astrocytes and Müller cells, which may influence tight junction formation and maturation. The aim of this study was to examine the changes in the trans-epithelial resistance (TER), as a measure of barrier integrity, on cell lines of epithelial origin (ECV304 and ARPE-19) following co-culture with glial cell lines (C6 and MIO-M1) or with the addition of medium conditioned by these cells. One cell line, ECV304, showed a significant increase in the TER in response to glial secreted factors whilst ARPE-19 did not. This finding suggests that ECV304 responds well to glial factors and may be useful for further studies of the factors that affect tight junction formation through glial cell induction in vitro.
Publisher: Elsevier BV
Date: 03-2023
DOI: 10.1016/J.SURVOPHTHAL.2022.11.004
Abstract: In this article, we present a review of patient-reported outcome measures (PROMs) used to evaluate the quality of life (QoL) in uveitis and provide a quality assessment of the psychometric properties of the PROMs, making it easier to choose the best questionnaire for uveitis. Our review included 158 articles. A total of 98 PROMs were used to measure QoL in uveitis and the National Eye Institute Visual Function Questionnaire 25 (NEI VFQ 25) was the most frequently used PROM in these studies. There were five uveitis-specific PROMs, but they were meant for either birdshot choroidopathy or cytomegalovirus (CMV) retinitis or paediatric uveitis. There are no PROMs developed explicitly for the more common, anterior uveitis, intermediate uveitis, panuveitis and chronic uveitis. The uveitis specific PROMs performed better in our quality assessment criteria compared to other PROMs. However, these PROMs were constructed using traditional classical test theory and have not been assessed using the modern family of psychometric assessment methods such as Rasch analysis. As new therapeutic modalities for uveitis such as the new biological agents and steroid implants continue to evolve, a comprehensive PROM will be increasingly valued in clinical trial settings to compare the effects of treatments from the patient perspective.
Publisher: Elsevier BV
Date: 03-2006
DOI: 10.1016/J.PRETEYERES.2005.11.001
Abstract: The retinal pigment epithelium (RPE) lying distal to the retina regulates the extracellular environment and provides metabolic support to the outer retina. RPE abnormalities are closely associated with retinal death and it has been claimed several of the most important diseases causing blindness are degenerations of the RPE. Therefore, the study of the RPE is important in Ophthalmology. Although visualisation of the RPE is part of clinical investigations, there are a limited number of methods which have been used to investigate RPE function. One of the most important is a study of the current generated by the RPE. In this it is similar to other secretory epithelia. The RPE current is large and varies as retinal activity alters. It is also affected by drugs and disease. The RPE currents can be studied in cell culture, in animal experimentation but also in clinical situations. The object of this review is to summarise this work, to relate it to the molecular membrane mechanisms of the RPE and to possible mechanisms of disease states.
Publisher: Springer Science and Business Media LLC
Date: 11-02-2016
DOI: 10.1007/S10633-016-9529-Y
Abstract: To explore early findings that in iduals with autism spectrum disorder (ASD) have reduced scotopic ERG b-wave litudes. Light-adapted (LA) and dark-adapted (DA) ERGs were produced by a range of flash strengths that included and extended the ISCEV standard from two subject groups: a high-functioning ASD group N = 11 and a Control group N = 15 for DA and N = 14 for LA ERGs who were matched for mean age and range. Flash strengths ranged from DA -4.0 to 2.3 log phot cd s m(-2) and LA -0.5 to 1.0 log phot cd s m(-2), and Naka-Rushton curves were fitted to DA b-wave litude over the first growth limb (-4.0 to -1.0 log phot cd s m(-2)). The derived parameters (V max, K m and n) were compared between groups. Scotopic 15-Hz flicker ERGs (14.93 Hz) were recorded to 10 flash strengths presented in ascending order from -3.0 to 0.5 log Td s to assess the slow and fast rod pathways, respectively. LA 30-Hz flicker ERGs, oscillatory potentials (OPs) and the responses to prolonged 120-ms ON-OFF stimuli were also recorded. The ISCEV LA b-wave litude produced by 0.5 log phot cd s m(-2) was lower in the ASD group (p 0.08) to the single flash stimuli, but there was a significant difference in the distribution for the LA b-wave litudes (corrected p = 0.006). The prolonged 120-ms ON responses were smaller in the ASD group (corrected p = 0.003), but the OFF response litude (p > 0.6) and ON and OFF times to peaks (p > 0.4) were similar between groups. The LA OPs showed an earlier bifurcation of OP2 in the younger ASD participants however, no other differences were apparent in the OPs or 30-Hz flicker waveforms. DA b-wave litudes fell below the control 5th centile of the controls for some in iduals including four ASD participants (36 %) at the 1.5 log phot cd s m(-2) flash strength and two (18%) ASD participants at the lower -2 log phot cd s m(-2) flash strength. However, across the 13 flash strengths, there were no significant group differences for b-wave litude's growth (repeated measures ANOVA p = 0.83). Nor were there any significant differences between the groups for the Naka-Rushton parameters (p > 0.09). No group differences were observed in the 15-Hz scotopic flicker phase or litude (p > 0.1), DA ERG a-wave litude or time to peak (p > 26). The DA b-wave time to peak at 0.5 log phot cd s m(-2) was longer in the ASD group (p = 0.04). Under LA conditions, the b-wave is reduced across the ASD group, along with the ON response of the prolonged flash ERG. Some ASD in iduals also show subnormal DA ERG b-wave litudes. These exploratory findings suggest there is altered cone-ON bipolar signalling in ASD.
Publisher: Informa UK Limited
Date: 05-2020
DOI: 10.1111/CXO.12940
Abstract: This review of the literature in visual search superiority in autism was intended to quantify the effect size of visual search performance in autism. Not all studies have found an advantage within the autistic population. Early findings on search superiority have led to different proposed mechanisms for the observed results. A review of feature search found that the effect size was low across 15 included studies (Cohen's d 0.089 [-0.150 to 0.293]). However, the effect size was larger for more complex search paradigms using a conjunctive search strategy with Cohen's d showing a moderate effect of 0.223 (0.087 to 0.293). The majority of studies were limited to a small s le size and biased toward the high-functioning end of the autistic spectrum. The overall results indicate that within the autism spectrum disorder population there is a low to moderate search advantage compared to typically developing in iduals.
Publisher: Springer Science and Business Media LLC
Date: 23-06-2021
DOI: 10.1007/S10633-021-09845-9
Abstract: To investigate if a lower luminance monochromatic LED stimulus could be used as an alternative to a high luminance white light for the clinical electrooculogram. Clinical electrooculograms were recorded in color normal participants (N = 23) aged 22.6 ± 1.2 years, 7 male and 16 female using the standard 100 cd.m The normalized LP:DTratio for the short wavelength LED (448 nm) was equivalent in litude and timing to the ISCEV standard EOG (p = .99). The LP:DTratio for the white (100 cd.m Consideration may be given to using a short wavelength monochromatic stimulus that is more comfortable for the subject than the current 100 cd.m
Publisher: Informa UK Limited
Date: 19-09-2022
Publisher: Springer Science and Business Media LLC
Date: 25-08-2012
DOI: 10.1007/S10633-012-9349-7
Abstract: Autism spectrum disorder (ASD) is a condition in which visual perception to both static and moving stimuli is altered. The aim of this study was to investigate the early cortical responses of subjects with ASD to simple patterns and moving radial rings using visual evoked potentials (VEPs). Male ASD participants (n = 9) and typically developing (TD) in iduals (n = 7) were matched for full, performance and verbal IQ (p > 0.263). VEPs were recorded to the pattern reversing checks of 50' side length presented with Michelson contrasts of 98 and 10 % and to the onset of motion-either expansion or contraction of low-contrast concentric rings (33.3 % duty cycle at 10 % contrast). There were no significant differences between groups in the VEPs elicited by pattern reversal checkerboards of high (98 %) or low (10 %) contrast. The ASD group had a significantly larger N160 peak (1.85 x) litude to motion onset VEPs elicited by the expansion of radial rings (p = 0.001). No differences were evident in contraction VEP peak litudes nor in the latencies of the motion onset N160 peaks. There was no evidence of a response that could be associated with adaptation to the motion stimulus in the interstimulus interval following an expansion or contraction phase of the rings. These data support a difference in processing of motion onset stimuli in this adult high-functioning ASD group compared to the TD group.
Publisher: Informa UK Limited
Date: 02-2022
DOI: 10.2147/OPTO.S355091
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 21-04-2014
Abstract: The light-rise of the electrooculogram is believed to originate from a substance released from the rods after dark adaptation. The identity of this "elusive" light-rise substance has not been demonstrated, and therefore a new perspective on the light-rise is presented. The light-rise is caused by the depolarization of the basolateral membrane of the retinal pigment epithelium (RPE) has become clearer in the last decade with the identification of calcium as the intracellular secondary messenger and the role of bestrophin as a regulator of intracellular stores of calcium and controlling the cytosolic calcium levels through L-type calcium channels. The light-rise depends upon a change from darkness to light, which triggers the intracellular cascade resulting in the depolarization of the basolateral membrane. The same intracellular signaling molecules, notably calcium and inositol triphosphate (IP3), are strongly implicated in this cascade. Recent studies have now led to a clearer understanding of the roles and functions of the ion channels and their contribution to the light-rise with IP3 regulating the release of calcium for intracellular stores. Given that calcium and IP3 are also regulators of phagocytosis, and that the initiation of rod outer segment phagocytosis is initiated with light-onset, it may be that the light-rise is generated in response to this physiological event. Therefore, the putative light-rise substance may not be released by the rods, but follow directly from IP3 release from the RPE's phospholipid membrane following the onset of light and the initiation of phagocytosis. The light rise substance, could be considered to be light itself.
Publisher: Wiley
Date: 17-02-2017
DOI: 10.1111/OPO.12350
Abstract: To determine whether there is an association with a congenital visual or hearing impairment ( VI or HI ) and Autism Spectrum Disorder (ASD) in children. A systematic literature review was performed using nine relevant databases limited to peer reviewed articles in English between 1994 and January 2016. The search identified 1248 articles after duplicates were removed with subsequent screening of the abstracts excluding a further 1199, resulting in 49 full‐text articles that were then independently assessed by five of the authors with a final 15 articles meeting the inclusion criteria. Bias assessment was determined through consensus of the first five authors. A meta‐analysis of the included studies was performed to estimate the relative risk of ASD in the VI and HI groups compared to the general population based on reported prevalence rates in similar geographical regions. Overall prevalence rates for ASD were calculated from the combined studies in the VI and HI populations. The overall prevalence of ASD in VI and HI populations was 19% (95% CI 13–25%) and 9% (95% CI 6–12%) respectively. The overall risk‐ratio of ASD was greater in the VI 31.0 times (95% CI 18.62–51.56) z = 13.21, p 0.001) and HI groups 14.1 times (95% CI 3.41–58.62 z = 3.65, p 0.001) compared to reported ASD prevalence in the general population. There is a high association of ASD in VI or HI children and therefore these populations should be assessed for ASD in the presence of a visual or hearing disability.
Publisher: Informa UK Limited
Date: 03-2021
Publisher: Springer Science and Business Media LLC
Date: 09-03-2017
Publisher: Springer Science and Business Media LLC
Date: 14-03-2018
Publisher: Elsevier BV
Date: 11-2023
Publisher: Informa UK Limited
Date: 10-2010
DOI: 10.2147/OPTO.S11476
Publisher: Informa UK Limited
Date: 11-2018
DOI: 10.1111/CXO.12799
Abstract: The standing potential of the eye exhibits a slow d ed oscillation under light and dark conditions that continues for at least 80 minutes. However, our understanding of the relationship between the slow dark and light oscillation has not been previously studied. The aim of this study was to explore through regression analysis a model of these oscillations in order to establish if they may have the same underlying cellular generators. Healthy participants undertook recordings of the standing potential using the electro-oculogram for 100 minutes. To explore the light oscillation, participants (n = 8) were dilated and performed an extended electro-oculogram protocol consisting of 15 minutes dark adaptation and 85 minutes of white light adaptation at 100 cd/m Ratios of the dark and light oscillations showed a significantly greater d ening of the dark oscillation compared to the light oscillation (p < 0.000). Regression analysis using a five-factor d ed sine function revealed significant differences in the parameters governing the d ening (p = 0.005) and period (p = 0.009) of the functions (R The results support a different underlying physiological mechanism for the light and dark oscillation of the clinical electro-oculogram. Future work will need to establish how the dark oscillation and dark trough of the clinical electro-oculogram arise.
Publisher: Frontiers Media SA
Date: 02-08-2023
DOI: 10.3389/FNINS.2023.1215097
Abstract: The retina and brain share similar neurochemistry and neurodevelopmental origins, with the retina, often viewed as a “window to the brain.” With retinal measures of structure and function becoming easier to obtain in clinical populations there is a growing interest in using retinal findings as potential biomarkers for disorders affecting the central nervous system. Functional retinal biomarkers, such as the electroretinogram, show promise in neurological disorders, despite having limitations imposed by the existence of overlapping genetic markers, clinical traits or the effects of medications that may reduce their specificity in some conditions. This narrative review summarizes the principal functional retinal findings in central nervous system disorders and related mouse models and provides a background to the main excitatory and inhibitory retinal neurotransmitters that have been implicated to explain the visual electrophysiological findings. These changes in retinal neurochemistry may contribute to our understanding of these conditions based on the findings of retinal electrophysiological tests such as the flash, pattern, multifocal electroretinograms, and electro-oculogram. It is likely that future applications of signal analysis and machine learning algorithms will offer new insights into the pathophysiology, classification, and progression of these clinical disorders including autism, attention deficit/hyperactivity disorder, bipolar disorder, schizophrenia, depression, Parkinson’s, and Alzheimer’s disease. New clinical applications of visual electrophysiology to this field may lead to earlier, more accurate diagnoses and better targeted therapeutic interventions benefiting in idual patients and clinicians managing these in iduals and their families.
Publisher: Springer Science and Business Media LLC
Date: 08-01-2011
DOI: 10.1007/S00417-010-1604-6
Abstract: To determine if the L-type calcium channel participates in the generation of the light-rise of the electro-oculogram (EOG) in man. The aim was to use nifedipine, a specific, L-type calcium channel inhibitor and determine the effects on the light-rise of the EOG in healthy participants. The EOG was recorded in 14 participants before and after a 10 mg oral dose of fast-acting nifedipine. The Arden index, time to peak of the EOGs and pulse were recorded before and after ingestion of nifedipine. The test-retest variability of the EOG's light-rise in the absence of nifedipine was performed on 11 of the participants. The mean ± SEM oral dose was 147 ± 9 μg/kg. Scotopic electroretinograms (ERGs) were recorded at four intensities (0.0067, 0.0849, 0.364 and 1.140 cd.s.m⁻²) in six participants before and after a 10 mg oral dose of nifedipine. The light-rise of the EOG was significantly reduced in five participants by -22.80 ± 5.6% (p = 0.021), whilst in four of the participants the light-rise increased by +15.7 ± 1.9% (p = 0.033). The results of the test-retest EOGs showed a range of -9.1 to +9.8% Arden index in the absence of nifedipine. Thus, the responses of five participants were not included in the analysis, as the change in the EOG with nifedipine was within this range. The differences in the time to peak of the light-rise were not significantly different in those that showed an increase (p = 0.33) or a decrease (p = 0.87) in the EOG after nifedipine. Pulse rate was not significantly different after nifedipine in the group that showed an increased light-rise (p = 0.77) or in those whose light-rise fell after nifedipine (p = 0.33). No significant effect was observed on the a- and b-wave litudes and implicit times for the scotopic components of the scotopic ERG. The L-type calcium channel contributes to the light-rise of the EOG in man.
Publisher: Informa UK Limited
Date: 07-04-2021
Publisher: MDPI AG
Date: 11-06-2023
DOI: 10.3390/BIOENGINEERING10060708
Abstract: Background: The electroretinogram is a clinical test used to assess the function of the photoreceptors and retinal circuits of various cells in the eye, with the recorded waveform being the result of the summated response of neural generators across the retina. Methods: The present investigation involved an analysis of the electroretinogram waveform in both the time and time–frequency domains through the utilization of the discrete wavelet transform and continuous wavelet transform techniques. The primary aim of this study was to monitor and evaluate the effects of treatment in a New Zealand rabbit model of endophthalmitis via electroretinogram waveform analysis and to compare these with normal human electroretinograms. Results: The wavelet scalograms were analyzed using various mother wavelets, including the Daubechies, Ricker, Wavelet Biorthogonal 3.1 (bior3.1), Morlet, Haar, and Gaussian wavelets. Distinctive variances were identified in the wavelet scalograms between rabbit and human electroretinograms. The wavelet scalograms in the rabbit model of endophthalmitis showed recovery with treatment in parallel with the time-domain features. Conclusions: The study compared adult, child, and rabbit electroretinogram responses using DWT and CWT, finding that adult signals had higher power than child signals, and that rabbit signals showed differences in the a-wave and b-wave depending on the type of response tested, while the Haar wavelet was found to be superior in visualizing frequency components in electrophysiological signals for following the treatment of endophthalmitis and may give additional outcome measures for the management of retinal disease.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Paul Constable.