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Optometry and Ophthalmology | Vision Science | Optical Technology |
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-10-2016
Abstract: To determine the corneal surfaces and lens contributions to ocular aberrations. There were 61 healthy participants with ages ranging from 20 to 55 years and refractions -8.25 diopters (D) to +3.25 D. Anterior and posterior corneal topographies were obtained with an Oculus Pentacam, and ocular aberrations were obtained with an iTrace aberrometer. Raytracing through models of corneas provided total corneal and surface component aberrations for 5-mm-diameter pupils. Lenticular contributions were given as differences between ocular and corneal aberrations. Theoretical raytracing investigated influence of object distance on aberrations. Apart from defocus, the highest aberration coefficients were horizontal astigmatism, horizontal coma, and spherical aberration. Most correlations between lenticular and ocular parameters were positive and significant, with compensation of total corneal aberrations by lenticular aberrations for 5/12 coefficients. Anterior corneal aberrations were approximately three times higher than posterior corneal aberrations and usually had opposite signs. Corneal topographic centers were displaced from aberrometer pupil centers by 0.32 ± 0.19 mm nasally and 0.02 ± 0.16 mm inferiorly disregarding corneal decentration relative to pupil center was significant for oblique astigmatism, horizontal coma, and horizontal trefoil. An object at infinity, rather than at the image in the anterior cornea, gave incorrect aberration estimates of the posterior cornea. Corneal and lenticular aberration magnitudes are similar, and aberrations of the anterior corneal surface are approximately three times those of the posterior surface. Corneal decentration relative to pupil center has significant effects on oblique astigmatism, horizontal coma, and horizontal trefoil. When estimating component aberrations, it is important to use correct object/image conjugates and heights at surfaces.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 31-08-2016
DOI: 10.1167/16.10.21
Abstract: This study compared neural resolution and detection limits of the human mid-/long-wavelength and short-wavelength cone systems with anatomical estimates of photoreceptor and retinal ganglion cell spacings and sizes. Detection and resolution limits were measured from central fixation out to 35° eccentricity across the horizontal visual field using a modified Lotmar interferometer. The mid-/long-wavelength cone system was studied using a green (550 nm) test stimulus to which S-cones have low sensitivity. To bias resolution and detection to the short-wavelength cone system, a blue (450 nm) test stimulus was presented against a bright yellow background that desensitized the M- and L-cones. Participants were three trichromatic males with normal visual functions. With green stimuli, resolution showed a steep central-peripheral gradient that was similar between participants, whereas the detection gradient was shallower and patterns were different between participants. Detection and resolution with blue stimuli were poorer than for green stimuli. The detection of blue stimuli was superior to resolution across the horizontal visual field and the patterns were different between participants. The mid-/long-wavelength cone system's resolution is limited by midget ganglion cell spacing and its detection is limited by the size of the M- and L-cone photoreceptors, consistent with previous observations. We found that no such simple relationships occur for the short-wavelength cone system between resolution and the bistratified ganglion cell spacing, nor between detection and the S-cone photoreceptor sizes.
Publisher: Optica Publishing Group
Date: 25-09-2020
DOI: 10.1364/BOE.400471
Abstract: Optical biometry uses interferometry to measure the axial length (AL) of the eye. Traditionally, one-variable regression formulas have converted the optical path length measured by a biometer to a geometric AL. An alternate calculation of axial length sums the in idual segments of the eye (sum-of-segments AL). This calculation has been shown to improve predictions of some intraocular lens power formulas when used in place of traditional axial length. Sum-of-segments ALs are determined from 13 refractive index models. As measured in 1695 eyes, these yield different ocular axial lengths. A path to standardization from these models is presented.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2019
DOI: 10.1097/OPX.0000000000001334
Abstract: Nominally plano ophthalmic prisms give autorefraction results similar to those predicted on the basis of how effective powers change with pantoscopic tilt, and magnifying lenses give autorefraction results similar to those predicted on the basis of vergence changes. Without appreciation of the optics involved, these effects might wrongly be considered artifacts. The purpose of this study was to investigate the interactions of autorefractors with lenses and prisms. There were 15 adult participants across three experiments, with a range of ages and refractions. In experiments 1 and 2, participants wore frames containing base-up and base-down nominally plano prisms. In experiment 3, participants wore a lens that produced either 6.3% magnification or 5.9% minification, depending on which surface faced the eye. Autorefracting instruments with different operating principles were used: Shin-Nippon SRW5000 autorefractor, Grand Seiko 5100K autorefractor, Hoya AR-530 autorefractor, a Complete Ophthalmic Analysis System–High Definition wavefront sensor, and Tomey FC-800 autorefractor. A theory on the likely effects of magnifying lenses was presented. For ophthalmic prisms, refractions showed results similar to those predicted on the basis of how effective prism powers change with pantoscopic tilt. As tilt increased, base-up prism gave more positive mean refractions and more negative horizontal/vertical astigmatism and vice versa for base-down prisms. In the presence of 10° tilt, 8Δ base-up prisms and 8Δ base-down prisms had different effects by a mean of 0.36 diopters. Magnifying lenses affected refractions similar to those predicted on the basis of vergence changes, with 6% magnification and minification producing mean changes of −11 and +8%, respectively, in absolute mean refraction. There was no strong evidence that different instruments had different effects. The results have implications for studies in which prisms and lenses are placed in the front eyes, such as accommodation studies using thick lenses close to the eyes to stimulate accommodation rather than by changing object distance.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2017
DOI: 10.1097/OPX.0000000000001037
Abstract: To investigate the effect of accommodation on central and peripheral axial lengths in young adult emmetropes and myopes. On-axis and peripheral axial lengths were measured with the Haag-Streit Lenstar in 83 young adult participants for 0D and 6D accommodation demands. A Badal system was used to both correct refractive errors and induce accommodation. Participants were emmetropes ( n = 29, mean spherical equivalent refraction +0.35 ± 0.35D), low myopes (32, −1.38 ± 0.73D), and higher myopes (22, −4.30 ± 0.73D). Ages were similar for all groups (22 ± 2 years). Pupils were dilated with 2.5% phenylephrine to allow a large field of measurement while maintaining active accommodation. Axial lengths were measured in 5° steps to ±30° across the horizontal visual field. With accommodation, axial length increased for all refractive groups at all positions, but with lessening effect away from fixation. Axial length changes were greater for higher myopes than for emmetropes on-axis (higher myopes 41 ± 14 μm, emmetropes 30 ± 12 μm, P = .005), for higher myopes than for low myopes at 30° nasal ( P = .03), and for the higher myopes than for the other groups at 20° nasal ( P .05). There were significant correlations between myopia and changes in axial length at all positions, with the highest correlation on-axis ( R 2 = 0.30, P .001). During accommodation, eye length increased out to at least ±30° visual angle in young adult myopes and emmetropes. The increase was significantly greater for higher myopes than for the other groups at some positions. At all positions, there were significant correlations between myopia and accommodation-induced changes in axial length.
Publisher: The Optical Society
Date: 04-02-2015
DOI: 10.1364/BOE.6.000702
Publisher: Optica Publishing Group
Date: 16-07-2021
DOI: 10.1364/BOE.427834
Abstract: The Stiles-Crawford effect of the first kind (SCE) is the phenomenon in which light entering the eye near the center of the pupil appears brighter than light entering near the edge. Previous investigations have found an increase in the directionality (steepness) of the effect as the testing location moves from the center of the visual field to parafoveal positions, but the effect of central field size has not been considered. The influence of field size on the SCE was investigated using a uniaxial Maxwellian system in which stimulus presentation was controlled by an active-matrix liquid crystal display. SCE directionality increased as field size increased from 0.5° to 4.7° diameter, although this was noted in four mild myopes and not in two emmetropes. The change with field size was supported by a geometric optics absorption model.
Publisher: Optica Publishing Group
Date: 17-11-2021
DOI: 10.1364/AO.403532
Abstract: We introduce the digital holographic microscope for recording in vivo human eye retinal structures. Current eye imaging technologies cannot provide images with resolutions better than 1 µm within depths of a few hundred micrometers. This can be improved with digital holography, in which a hologram of the eye captured with digital camera contains information about structures over the full depth of the eye. This information can be reconstructed either optically or numerically. Our hologram recording scheme utilizes working principles of the off-axis digital holographic microscope, designed for reflective micro-object investigation. The eye cornea and lens form the microscope objective. We can record in vivo digital holograms of the human eye retina with resolution after reconstruction of at least 1.3 micrometer.
Publisher: Wiley
Date: 19-05-2016
DOI: 10.1111/OPO.12284
Abstract: Retinal anatomical studies have used the Drasdo & Fowler three-refracting surface schematic eye to convert between retinal distances and object field angles. We compared its performance at this task with those of more sophisticated four-refracting surface schematic eyes. Raytracing was performed for Drasdo & Fowler, Lotmar, Navarro, Liou & Brennan, Kooijman and Atchison schematic eyes, and some of their variants. The Drasdo & Fowler eye gives a greater rate of change of object field angle with retinal distance at the retinal centre of about 5% than the other schematic eyes. This rate of change also increases much more quickly into the peripheral retina for the Drasdo & Fowler eye than for the other eyes. The reason for these differences is only that the Drasdo & Fowler eye is shorter than the other eyes. The relationship between retinal distance and visual field angle appears robust to changes in retinal radius of curvature when the retina is spherical. The retinal asphericity of Kooijman and Atchison eyes appears to play a role beyond 14 mm (~50°). Changing the length of the Drasdo & Fowler eye, to match those of the four-refracting surface schematic eyes, gives similar relationships between retinal distance and object field angle up to a retinal distance of approximately 14 mm (~50°). The relationship will change with refractive error as this is related to axial length and to retinal shape, and this should be taken into consideration for accurate conversions. For distances and angles beyond 14 mm and ~50°, retinal shape should be taken into account.
Publisher: Wiley
Date: 23-12-2014
DOI: 10.1111/OPO.12182
Abstract: To estimate refractive indices used by the Lenstar biometer to translate measured optical path lengths into geometrical path lengths within the eye. Axial lengths of model eyes were determined using the IOLMaster and Lenstar biometers comparing those lengths gave an overall eye refractive index estimate for the Lenstar. Using the Lenstar Graphical User Interface, we noticed that boundaries between media could be manipulated and opposite changes in optical path lengths on either side of the boundary could be introduced. Those ratios were combined with the overall eye refractive index to estimate separate refractive indices. Furthermore, Haag-Streit provided us with a template to obtain 'air thicknesses' to compare with geometrical distances. The axial length estimates obtained using the IOLMaster and the Lenstar agreed to within 0.01 mm. Estimates of group refractive indices used in the Lenstar were 1.340, 1.341, 1.415, and 1.354 for cornea, aqueous, lens, and overall eye, respectively. Those refractive indices did not match those of schematic eyes, but were close in the cases of aqueous and lens. Linear equations relating air thicknesses to geometrical thicknesses were consistent with our findings. The Lenstar uses different refractive indices for different ocular media. Some of the refractive indices, such as that for the cornea, are not physiological therefore, it is likely that the calibrations in the instrument correspond to instrument-specific corrections and are not the real optical path lengths.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-09-2016
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2017
DOI: 10.1097/OPX.0000000000001130
Abstract: The main problem with phakometry is the low visibility of the third Purkinje image. We built a phakometer using Bessel beams, which have properties of being resistant to diffraction and the potential for self-reconstruction. This instrument had lenticular images three times brighter than those of a conventional phakometer. To investigate Purkinje image brightness, accuracy, and repeatability of a “Bessel” phakometer compared with those of a conventional phakometer. Phakometers were developed with a telecentric imaging system focused at the pupil plane of the eye to capture anterior cornea, anterior lens (PIII), and posterior lens (PIV) Purkinje images. A Bessel beam was generated by a diode laser beam passing through a high-powered doublet with a central obstruction. Software was used to determine image sizes and estimate lens anterior and posterior surface radii of curvature ( R a , R p ), equivalent refractive index (RI), and equivalent power ( F ). The Bessel phakometer's accuracy was assessed using a model eye. Repeatability (interobserver and intraobserver) and Purkinje images brightnesses of Bessel and conventional phakometers were assessed with six participants. The lens parameters of the model eye determined by the Bessel phakometer were similar to those provided by the model eye's manufacturer with differences (manufacturer − Bessel) in R a and R p , RI, and F of +1.18 mm, 0.18 mm, +0.0053, and −0.55 D, respectively. The intraobserver repeatabilities for the Bessel and conventional phakometers were similar. The interobserver repeatabilities of R a , R p , and RI for the Bessel phakometer were almost half those (i.e., two times better) for the conventional phakometer. Brightnesses of PIII and PIV were approximately three times higher with the Bessel phakometer than with the conventional phakometer. The Bessel beam phakometer provided accurate estimates of lens parameters of a model eye and produced brighter Purkinje images and better interobserver repeatability than that of a conventional phakometer.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 02-09-2016
Publisher: The Optical Society
Date: 21-02-2018
DOI: 10.1364/BOE.9.001272
Publisher: Wiley
Date: 27-12-2016
DOI: 10.1111/OPO.12265
Abstract: To explore the effect of small-aperture optics, designed to aid presbyopes by increasing ocular depth-of-focus, on measurements of the visual field. Simple theoretical and ray-tracing models were used to predict the impact of different designs of small-aperture contact lenses or corneal inlays on the proportion of light passing through natural pupils of various diameters as a function of the direction in the visual field. The left eyes of five healthy volunteers were tested using three afocal, hand-painted opaque soft contact lenses (www.davidthomas.com). Two were opaque over a 10 mm diameter but had central clear circular apertures of 1.5 and 3.0 mm in diameter. The third had an annular opaque zone with inner and outer diameters of 1.5 and 4.0 mm, approximately simulating the geometry of the KAMRA inlay (www.acufocus.com). A fourth, clear lens was used for comparison purposes. Visual fields along the horizontal meridian were evaluated up to 50° eccentricity with static automated perimetry (Medmont M700, stimulus Goldmann-size III www.medmont.com). According to ray-tracing, the two lenses with the circular apertures were expected to reduce the relative transmittance of the pupil to zero at specific field angles (around 60° for the conditions of the experimental measurements). In contrast, the annular stop had no effect on the absolute field but relative transmittance was reduced over the central area of the field, the exact effects depending upon the natural pupil diameter. Experimental results broadly agreed with these theoretical expectations. With the 1.5 and 3.0 mm pupils, only minor losses in sensitivity (around 2 dB) in comparison with the clear-lens case occurred across the central 10° radius of field. Beyond this angle, sensitivity losses increased, to reach about 7 dB at the edge of the measured field (50°). The field results with the annular stop showed at most only a slight loss in sensitivity (≤3 dB) across the measured field. The present theoretical and experimental results support earlier clinical findings that KAMRA-type annular stops, unlike circular artificial pupils, have only minor effects on measurements of the visual field.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-04-2016
Abstract: We determined whether human ocular lens position is influenced by gravity. Anterior chamber depth (ACD) and lens thickness (LT) were determined with a Haag-Streit Lenstar LS900 for right eyes of participants in two age groups, with a young group of 13 participants aged 18 to 21 years (mean, 21 years SD, 1 year) and an older group of 10 participants aged 50 to 63 years (mean, 58 years SD, 4 years). There were two sessions for each participant separated by at least 48 hours, with one session for the usual upright head position and one session for a downwards head position. In a session, testing was done for minimum accommodation followed by testing at maximum accommodation. A drop of 2% pilocarpine nitrate was instilled, and testing was repeated after 30 minutes under minimum and maximum accommodation conditions. Gravity, manipulated through head posture, affected ACD for young adult and older adult groups but mean effects were only small, ranging from 0.04 to 0.12 mm, and for the older group required the instillation of an accommodation-stimulating drug. Gravity had a weakly significant effect on LT for the young group without accommodation or a drug, but the effect was small at 0.04 ± 0.06 mm (mean ± SD, P = 0.04). There is a small but real effect of gravity on crystalline lens position, manifested as reduction in ACD at high levels of accommodative effort with the head in a downwards position. This provides evidence of the ability of zonules to slacken during strong accommodation.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2015
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2016
DOI: 10.1097/OPX.0000000000000954
Abstract: To investigate the operation of the Shin-Nippon/Grand Seiko autorefractor and whether higher-order aberrations affect its peripheral refraction measurements. Information on instrument design, together with parameters and equations used to obtain refraction, was obtained from a patent. A model eye simulating the operating principles was tested with an optical design program. Effects of induced defocus and astigmatism on the retinal image were used to calibrate the model eye to match the patent equations. Coma and trefoil were added to assess their effects on the image. Peripheral refraction of a physical model eye was measured along four visual field meridians with the Shin-Nippon/Grand Seiko autorefractor SRW-5000 and a Hartmann-Shack aberrometer, and simulated autorefractor peripheral refraction was derived using the Zernike coefficients from the aberrometer. In simulation, the autorefractor’s square image was changed in size by defocus, into rectangles or parallelograms by astigmatism, and into irregular shapes by coma and trefoil. In the presence of 1.0 D oblique astigmatism, errors in refraction were proportional to the higher-order aberrations, with up to 0.8 D sphere and 1.5 D cylinder for ±0.6 μm of coma or trefoil coefficients with a 5-mm-diameter pupil. For the physical model eye, refraction with the aberrometer was similar in all visual field meridians, but refraction with the autorefractor changed more quickly along one oblique meridian and less quickly along the other oblique meridian than along the horizontal and vertical meridians. Simulations predicted that higher-order aberrations would affect refraction in oblique meridians, and this was supported by the experimental measurements with the physical model eye. The autorefractor’s peripheral refraction measurements are valid for horizontal and vertical field meridians, but not for oblique field meridians. Similar instruments must be validated before being adopted outside their design scope.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2019
DOI: 10.1097/OPX.0000000000001328
Abstract: Ophthalmic imaging instruments that require stable fixation can benefit by using Bessel beams in the form of monitor-based Bessel images. The purpose of this study was to investigate fixation stability using laser Bessel and Gaussian beams and monitor-based images of these targets. The right eyes of 16 participants were presented with seven fixation targets: monitor-based images of a bull's eye/cross hair, a Gaussian beam, a Bessel beam with four rings and a Bessel beam with three rings laser Gaussian beam, laser Bessel beam with four rings, and laser Bessel beam with three rings. Participants fixated target centers for five runs, in which each run presented the seven targets for 20 seconds each. An Eye Tribe tracker s led eye positions at 30 Hz. Standard deviations along horizontal (σ x ) and vertical meridians (σ y ) and areas of bivariate contour ellipses (BCEAs) of fixation positions were calculated, and statistical significances of target differences for these parameters were determined. Average σ x , σ y , and BCEAs ranged from 0.26 to 0.35°, 0.38 to 0.55°, and 0.78 to 1.31 degrees 2 , respectively. Target differences in σ x (χ 2 6 = 13.0, P = .04), (σ y ) (χ 2 6 = 36.819, P .001), and BCEA (χ 2 6 = 34.406, P .001) were statistically significant. There were significant post hoc differences between some of the target pairs for σ y and BCEA, but not for σ x . Monitor-based Bessel beam targets provided significantly smaller σ y and BCEAs than the bull's eye/cross hair combination and the monitor- and laser-based Gaussian beam targets. Monitor-based images of Bessel beams provided better fixation targets than did a bull's eye/cross hair combination, monitor-based Gaussian images, and laser Gaussian beams, but no claim can be made that laser Bessel beams provide better fixation targets than do laser Gaussian beams. Monitor-based Bessel images should be useful for ophthalmic imaging instruments requiring stable fixation.
Publisher: The Optical Society
Date: 05-08-2015
DOI: 10.1364/BOE.6.003235
Publisher: The Optical Society
Date: 20-06-2018
DOI: 10.1364/BOE.9.003178
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2016
Publisher: The Optical Society
Date: 05-04-2017
DOI: 10.1364/BOE.8.002386
Publisher: OSA
Date: 2016
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2019
DOI: 10.1097/OPX.0000000000001321
Abstract: Nominally plano prisms can have appreciable refractive errors that exceed the usual prescribing step of 0.25 D, particularly when an eye rotates to view off-axis objects. The purpose of this study was to determine theoretically the refractive power effects of nominally plano-refracting power prisms. Plano prisms with zero refraction were designed for the as-worn condition. A basic method was developed to determine refractive effects in the presence of pantoscopic tilt. A refined method was developed that considers the eye rotating behind the lens, and this and the basic method were compared with accurate raytracing. Plano prisms of 4 and 8 Δ were designed with astigmatic back surfaces to compensate for oblique incidence, and tangential and sagittal image vergence errors were investigated for base-up (BU) and base-down (BD) directions, 0 and −3.33 D object vergences, and pantoscopic tilts up to 10°. Basic and refined results did not differ from accurate results by more than 0.04 and 0.08 D, respectively. Errors for 8 Δ prisms were approximately twice those for 4 Δ prisms. Errors were approximately proportional to tilt. With 10° tilt, the errors ranged between −0.65 D/−0.23 D (8 Δ BD, −3.33 D object vergence) and +0.36 D/+0.15 D (8 Δ BU, 0 D object vergence). Sagittal errors were generally about one third of corresponding tangential errors. In the presence of tilt, BU prisms had positive errors, and BD prisms had similar, but negative, errors for distance objects. At −3.33 D object vergence with tilt, negative errors for BD were greater than positive errors for BU. When the eye rotates to look at objects at different positions, errors can increase beyond those occurring on-axis. When designed for nontilted conditions, but then subjected to tilt or to viewing off-axis objects, plano prisms can have errors exceeding the usual prescribing step of 0.25 D.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 28-06-2016
Abstract: To investigate mirror symmetry of peripheral ocular aberrations in fellow eyes of iso- and anisomyopes. Peripheral aberration was measured over the central 42° × 32° visual field for a 5-mm pupil in both eyes of 19 isomyopic (spherical equivalent refraction M [right/left]: -2.5 ± 2.1 diopters [D]/-2.7 ± 2.3 D) and 10 anisomyopic (M: -4.0 ± 1.8 D/-4.3 ± 2.8 D) young adults. Isomyopes had less than 1.0 D fellow eye refraction difference and anisomyopes had between 1.0 D and 2.6 D fellow eye differences (mean difference: 1.3 ± 0.6 D). Orthogonal regression of Zernike coefficients determined right-left eye correlations in isomyopes. For anisomyopes, higher and lower myopic eye coefficients were compared. For isomyopes, the percentages of visual field locations with significant coefficient correlations between fellow eyes varied from 100% for astigmatism ( ) to 18% for tetrafoil ( ). Positive correlations were found for , , , , , and , and negative correlations were found for , , , , and coefficients, indicating that the signs are different for corresponding locations of fellow eyes for the last five of these coefficients. Slopes of correlations were not different from ± 1, except for , , and (+0.95, -0.97, and +0.52, respectively). In anisomyopes, significant but small fellow eye differences were found for only and coefficients, with significant interactions between anisometropia and field position for only two coefficients. Peripheral aberration coefficients across the visual field show mirror symmetry in isomyopes, and in a pooled data set the coefficients with negative correlations require sign changes for left eye data. Anisometropia contributes no more to peripheral aberration differences between fellow eyes than could be expected on the basis of refraction differences between people.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2018
DOI: 10.1097/OPX.0000000000001180
Abstract: Myopia prevalence rates differ between racial groups. If the growth of the eye is sensitive to differences in optical input, the difference in spherical aberration between East Asian and Caucasian eyes found in this study may be important in understanding myopia development. The aim of this study was to determine differences in peripheral wavefront aberrations between two racial groups. Wavefront aberrations were measured using a COAS-HD aberrometer across the 42 × 32° central visual field on 37 right eyes of young adults (18 Caucasians, 19 East Asians mean age 21.5 ± 2.4 years). The mean spherical equivalent refraction was −1.94 ± 1.63 diopters (D) with a range of −5.87 to +0.16 D. Effect of race and visual field position on refractions, in idual Zernike aberration coefficients up to the fourth order, higher-order root-mean-square aberration, and total root-mean-square aberration were assessed by repeated-measures analysis of covariance. Caucasians and East Asians had similar relative peripheral myopia across the visual field. All higher-order aberration coefficients were affected by visual field position. Race had no significant effect on any higher-order Zernike coefficient, but the difference in mean vertical coma coefficient C 3 −1 across the visual field (i.e., average of 38 field locations) approached significance, being less positive in Caucasians than in East Asians ( P = .08). When correction was made for the Caucasian group being slightly less myopic than the East Asian group, spherical aberration coefficient C 4 0 was less positive in Caucasians than in East Asians by 0.04 μm ( P = .001). The rates of change of coma coefficients across the field were not affected by race. Caucasians and East Asians had similar relative peripheral myopia, but with less positive spherical aberration coefficient in Caucasians than in East Asians. It remains to be determined whether aberrations have a role in the difference of myopia prevalence rates in different countries.
Publisher: OSA
Date: 2017
Publisher: Wiley
Date: 07-2022
DOI: 10.1111/OPO.13021
Abstract: To determine whether accommodative errors in emmetropes and myopes are systematically different, and the effect of using different instruments and metrics. Seventy‐six adults aged 18–27 years comprising 24 emmetropes (spherical equivalent refraction of the dominant eye +0.04 ± 0.03 D) and 52 myopes (−2.73 ± 0.22 D) were included. Accommodation responses were measured with a Grand Seiko WAM‐5500 and a Hartmann–Shack Complete Ophthalmic Analysis System aberrometer, using pupil plane (Zernike and Seidel refraction) and retinal image plane (neural sharpness—NS and visual Strehl ratio for modulation transfer function—VSMTF) metrics at 40, 33 and 25 cm. Accommodation stimuli were presented to the corrected dominant eye, and responses, referenced to the corneal plane, were determined in the fellow eye. Linear mixed‐effects models were used to determine influence of the refractive group, the measurement method, accommodation stimulus, age, race, parental myopia, gender and binocular measures of heterophoria, accommodative convergence/accommodation and convergence accommodation/convergence ratios. Lags of accommodation were affected significantly by the measurement method ( p 0.001), the refractive group ( p = 0.003), near heterophoria ( p = 0.002) and accommodative stimulus ( p 0.05), with significant interactions between some of these variables. Overall, emmetropes had smaller lags of accommodation than myopes with respective means ± standard errors of 0.31 ± 0.08 D and 0.61 ± 0.06 D ( p = 0.003). Lags were largest for the Grand Seiko and Zernike defocus, intermediate for NS and VSMTF, and least for Seidel defocus. The mean lag of accommodation in emmetropes is approximately equal to the previously reported depth of focus. Myopes had larger (double) lags than emmetropes. Differences between methods and instruments could be as great as 0.50 D, and this must be considered when comparing studies and outcomes. Accommodative lag increased with the accommodation stimulus, but only for methods using a fixed small pupil diameter.
Publisher: Wiley
Date: 04-01-2023
DOI: 10.1111/OPO.13084
Abstract: Eye length increases during accommodation, both on‐axis and in the periphery. The aim of this study was to determine whether the peripheral choroid thins with accommodation and to determine the relationship with eye length changes measured at the same location. Subjects included 53 young adults in good ocular and general health, with 19 emmetropes and 34 myopes. Measurements from the right eye were made for 0 D and 6 D accommodation stimuli for ±30° horizontal visual field/retinal locations in 10° steps. Valid eye length and choroidal thickness measurements were obtained for 37 and 47 participants, respectively, and both measures were taken for 31 participants. 2.5% phenylephrine was instilled to dilate the pupils. Participants turned their eyes, without head movement, to fixate targets and to make the target ‘as clear as possible’ during measurements. Correction was made for the influence of lens thickness changing at different peripheral angles. Choroidal thickness was measured with a spectral‐domain‐Optical Coherence Tomographer. For peripheral images, the internal cross target on the capture screen was moved from the centre to 17.25° nasal/temporal positions. In accordance with previous literature, eye length increased with accommodation. The greatest change (mean ± SD) of 41 ± 17 μm occurred at the centre, with a mean change across the locations of 33 μm. There were no significant differences between emmetropes and myopes. Choroidal thickness decreased with accommodation, with changes being about two‐thirds of those occurring for eye length. The greatest change of −30 ± 1 μm occurred at the centre, with a mean change of −21 μm. Greater choroidal thinning occurred for myopes than for emmetropes (23 ± 11 vs. 17 ± 8 μm, p = 0.02). With accommodation, eye length increased and the choroid thinned, at both central and peripheral positions. Choroidal thinning accounted for approximately 60% of the eye length increase across the horizontal ±30°.
Publisher: Wiley
Date: 11-12-2013
DOI: 10.1111/OPO.12095
Abstract: The eye rotation approach for measuring peripheral eye length leads to concern about whether the rotation influences results, such as through pressure exerted by eyelids or extra-ocular muscles. This study investigated whether this approach is valid. Peripheral eye lengths were measured with a Lenstar LS 900 biometer for eye rotation and no-eye rotation conditions (head rotation for horizontal meridian and instrument rotation for vertical meridian). Measurements were made for 23 healthy young adults along the horizontal visual field (± 30°) and, for a subset of eight participants along the vertical visual field (± 25°). To investigate the influence of the duration of eye rotation, for six participants measurements were made at 0, 60, 120, 180 and 210 s after eye rotation to ± 30° along horizontal and vertical visual fields. Peripheral eye lengths were not significantly different for the conditions along the vertical meridian (F1,7 = 0.16, p = 0.71). The peripheral eye lengths for the conditions were significantly different along the horizontal meridian (F1,22 = 4.85, p = 0.04), although not at in idual positions (p ≥ 0.10) and were not important. There were no apparent differences between the emmetropic and myopic groups. There was no significant change in eye length at any position after maintaining position for 210 s. Eye rotation and no-eye rotation conditions were similar for measuring peripheral eye lengths along horizontal and vertical visual field meridians at ± 30° and ± 25°, respectively. Either condition can be used to estimate retinal shape from peripheral eye lengths.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-10-2014
Abstract: People with diabetes have accelerated age-related biometric ocular changes compared with people without diabetes. We determined the effect of type 1 diabetes on litude of accommodation. There were 43 participants (33 ± 8 years) with type 1 diabetes and 32 (34 ± 8 years) age-balanced controls. There was no significant difference in mean equivalent refractive error and visual acuity between the groups. Amplitude of accommodation was measured using two techniques: objective by determining the accommodative response to a stimulus in a COAS-HD wavefront aberrometer and subjective with a Badal hand optometer. Influences of age and diabetes duration on litude of accommodation were analyzed using multiple regression analysis. People with diabetes had lower objective (2.7 ± 1.6 diopters [D]) and subjective (4.0 ± 1.7 D) litudes than controls (objective 4.1 ± 2.1 D, subjective 5.6 ± 2.1 D). Across both groups, objective litude was less than subjective litude by 1.4 ± 1.2 D. For objective litude and the whole group, the duration of diabetes contributed 57% variation to the loss of litude relative to that provided by age. For the objective litude and only the diabetes group, this was 78%. For subjective litude, the corresponding proportions were 68% and 103%. Lowered litude of accommodation exists in in iduals with type 1 diabetes when compared with age-matched controls. The loss correlated strongly with duration of diabetes. The results suggest that in iduals with diabetes will experience presbyopia earlier in life than people without diabetes, mainly due to changes in the lens.
Publisher: Wiley
Date: 29-03-2017
DOI: 10.1111/OPO.12359
Abstract: To investigate whether retinal shape is different between East Asians and Caucasians. There were 36 East Asian and 40 Caucasian young adults, with refractions between +0.75D and −5.50D. Peripheral eye lengths were obtained after pupil dilation using the Lenstar partial coherence interferometer. Measurements were obtained along the horizontal and vertical meridians of the visual field out to ±35° and ±30°, respectively, in 5° steps. Retinal co‐ordinates were estimated using a validated method from the peripheral eye length measurements and ray‐tracing through a modified Le Grand full theoretical eye. Rays were directed normally towards the anterior cornea. Retinal shapes were described in terms of vertex radius of curvature ( R v ), asphericity ( Q ) and equivalent radius of curvature ( R E q ) along both horizontal and vertical meridians. R v was smaller in East Asian than in Caucasians (mean difference ± 95% CI −0.7 ± 0.5 mm), along the horizontal meridian than the vertical meridian (−1.2 ± 0.6 mm), and in myopia than in emmetropia (−1.0 ± 0.6 mm). R v along the horizontal meridian, but not along the vertical meridian, became smaller as myopia increased. Q did not vary significantly with meridian, refraction group or race. The same pattern of results occurred for R E q as for R v . The percentage differences of heights under the estimated retinal surfaces showed steeper retinas in East Asians than in Caucasians the differences between East Asian and Caucasian emmetropes were 2.5% and % along horizontal and vertical meridians, respectively, and corresponding differences for myopes were 4.6% and 1.8%. East Asians had steeper retinas than Caucasians. The horizontal meridian had steeper retinas than the vertical meridian. Myopes had steeper retinas than emmetropes. Racial differences in retinal shape in both emmetropes and myopes, combined with the high prevalence of myopia in East Asia, suggest that retinal shape may play a role in myopia development.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2016
DOI: 10.1097/OPX.0000000000000905
Abstract: To investigate how peripheral refraction and peripheral eye length are related to retinal shape. Relative peripheral refraction (RPR) and relative peripheral eye length (RPEL) were determined in 36 young adults ( M +0.75D to −5.25D) along horizontal and vertical visual field meridians out to ±35° and ±30°, respectively. Retinal shape was determined in terms of vertex radius of curvature R v , asphericity Q , and equivalent radius of curvature R Eq using a partial coherence interferometry method involving peripheral eye lengths and model eye raytracing. Second-order polynomial fits were applied to RPR and RPEL as functions of visual field position. Linear regressions were determined for the fits’ second order coefficients and for retinal shape estimates as functions of central spherical refraction. Linear regressions investigated relationships of RPR and RPEL with retinal shape estimates. Peripheral refraction, peripheral eye lengths, and retinal shapes were significantly affected by meridian and refraction. More positive (hyperopic) relative peripheral refraction, more negative RPELs, and steeper retinas were found along the horizontal than along the vertical meridian and in myopes than in emmetropes. RPR and RPEL, as represented by their second-order fit coefficients, correlated significantly with retinal shape represented by R Eq . Effects of meridian and refraction on RPR and RPEL patterns are consistent with effects on retinal shape. Patterns derived from one of these predict the others: more positive (hyperopic) RPR predicts more negative RPEL and steeper retinas, more negative RPEL predicts more positive relative peripheral refraction and steeper retinas, and steeper retinas derived from peripheral eye lengths predict more positive RPR.
Publisher: Wiley
Date: 12-12-2022
DOI: 10.1111/OPO.12932
Abstract: Human peripheral detection performance is affected by optical factors such as defocus and higher order aberrations. From optical theory, we would expect defocus to produce local depressions (notches) in the contrast sensitivity function (CSF). However, such notches have not been observed in peripheral vision, and it is unknown whether human peripheral vision can detect local depressions (notches) in the CSF, such as those produced by monochromatic defocus when all monochromatic ocular aberrations are corrected. The purpose of the study was to identify such notches. Participants were three adult emmetropes. Following full adaptive optics correction, on-axis and 20° nasal visual field detection CSFs in monochromatic light were measured for the right eye with a 7 mm diameter pupil, both without and with ±2 D defocus, and with separate determinations for horizontal and vertical gratings. Defocused CSFs were compared with predictions based on theoretical modulation transfer functions. Notches in the monochromatic defocused CSFs were identified for peripheral vision at optically predicted spatial frequencies with other monochromatic ocular aberrations corrected, provided that there was adequate spatial frequency s ling. The spatial frequencies of notches were similar to those predicted from optical theory, but their depths (0.3 to 0.9 log unit) were smaller than predicted. With fine spatial frequency s ling, notches were identified in defocused monochromatic CSFs when all other monochromatic ocular aberrations were corrected, both on-axis and at 20° eccentricity. Unless recognised as such, notches may contribute to noise in through-focus detection measurements of peripheral visual performance.
Publisher: Wiley
Date: 13-08-2021
DOI: 10.1111/OPO.12855
Abstract: To measure the Stiles-Crawford effect of the first kind (SCE-I), corresponding to central vision, with innovative technology to evaluate changes in the directionality and photoreceptor alignment with accommodation. A uniaxial Maxwellian system (spot size in pupil 0.5 mm diameter) was employed, incorporating a spatial light modulator to flicker at 2 Hz between two 2.3° fields corresponding to test (peripheral pupil) and reference (pupil centre) positions. Participants determined thresholds at 13 positions along the horizontal pupil meridian by indicating if the test field was brighter or dimmer than the reference field. Thresholds were determined by a staircase procedure after four reversals at each pupil location. After pupil dilation, seven emmetropes were tested at 0 D to 6 D accommodation stimulus levels in 2 D intervals. Data were fit by the Gaussian function, both when the fits were unforced or forced to pass through the sensitivity expected for the reference point. Directionality (ρ) and peak location values Regression slopes for ρ as a function of accommodation stimulus were not significant. There was a tendency for Directionality did not change with accommodation, but the pupil peak location showed a significant temporal shift of approximately 0.62 mm with 6 D accommodation stimulus. It is possible that substantial changes in the directionality and a shift in the direction of peak location might occur at very high levels of accommodation.
Publisher: Wiley
Date: 17-02-2017
DOI: 10.1111/OPO.12354
Abstract: To determine differences in peripheral aberrations in hyperopic, emmetropic and myopic groups. Cycloplegic peripheral aberrations for 5 mm pupils were measured at 39 locations across 42° × 32° of right eye visual fields with a COAS ‐ HD Hartmann‐Shack aberrometer in nine hyperopes (mean age 29 ± 5 years, spherical equivalent refraction M + 1.47 ± 0.58 D), 20 emmetropes (28 ± 7 years, +0.06 ± 0.36 D) and 20 myopes (27 ± 6 years, −2.55 ± 1.82 D). Relative peripheral refraction error RPRE and 3rd–4th order Zernike coefficients were compared between the groups. Hyperopes and emmetropes had relative peripheral myopia across the visual field, with considerable nasal‐temporal asymmetry for both groups and superior‐inferior asymmetry for hyperopes. Myopes had minimal RPRE along the horizontal meridian, but myopic RPRE along the vertical meridian which was less than the other groups. There was little difference between groups in astigmatic components or higher‐order Zernike coefficients, except for fourth‐order spherical aberration which was more positive in hyperopes than in both emmetropes (mean difference ±95% CI = +0.05 ± 0.05 μm, p = 0.03) and myopes (+0.07 ± 0.04 μm, p = 0.003). Coma changed rapidly across the visual field with similar rates for all groups. Hyperopes and emmetropes had greater relative peripheral myopia than myopes. There was asymmetry in RPRE along the vertical meridian for hyperopes which was not present in the emmetropes, suggesting there may be asymmetries in peripheral eye length along the vertical meridian for the former. Higher‐order aberrations were affected by field eccentricity, but refractive error affected only the spherical aberration coefficient, which was more positive for hyperopes than for other groups.
Publisher: Optica Publishing Group
Date: 12-2020
DOI: 10.1364/BOE.406101
Abstract: A combination of human subject data and optical modelling was used to investigate unexpected nasal-temporal asymmetry in peripheral refraction with an aspheric myopia control lens. Peripheral refraction was measured with an auto-refractor and an aberrometer. Peripheral refraction with the lens was highly dependent upon instrument and method (e.g. pupil size and the number of aberration orders). A model that did not account for on-eye conformation did not mirror the clinical results, but a model assuming complete lens conformation to the anterior corneal topography accounted for the positive shift in clinically measured refraction at larger nasal field angles. The findings indicate that peripheral refraction of highly aspheric contact lenses is dependent on lens conformation and the method of measurement. These measurement methods must be reported, and care must be used in interpreting results.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2014
Publisher: The Optical Society
Date: 13-03-2015
DOI: 10.1364/BOE.6.001282
Publisher: Wiley
Date: 20-12-2022
DOI: 10.1111/OPO.12936
Abstract: To determine, through simulations, the likely validity of Grand-Seiko autorefractors with annular targets in peripheral refraction. Using a physical model eye, the distance inside the eye to which the Grand Seiko AutoRef/Keratometer WAM-5500 beam was converging and the effective size of its outer diameter at the cornea were determined. Grand-Seiko refraction was calculated from R The instrument beam was determined to be converging towards the eye to a distance of 24.4 mm behind the corneal vertex, with a 2.46 mm effective size outer diameter of the beam at the anterior cornea. The Grand-Seiko refractions provided accurate estimates of peripheral refraction for the model eyes. The results were closer to Zernike refractions than to Zernike paraxial refraction. Spherical aberration influenced refraction by up to 0.5 D, and peripheral coma had limited influence. Grand-Seiko autorefractors in current use, and having a circular annulus with an ingoing effective outer diameter at the front of the eye of about 2.4 mm, are likely to give valid peripheral refractions.
Publisher: Wiley
Date: 20-12-2022
DOI: 10.1111/OPO.12933
Abstract: To study the optical principles and properties of autorefractors that use the image-size principle in which the size of the reimaged retinal image determines refraction. The retinal illumination and reimaging of the retinal image were described, as were variations in the basic system. Imaging was determined for systems in which the light source is either erging or converging as it passes into the eye. Equations were determined to describe the dependence of refraction on the heights and angles of incoming and outgoing beams, and refraction error was determined when eye position was not correct. The fundamental refraction equation is For image-size principle autorefractors, simple equations describe the dependence of measured refraction on the height and angle of the instrument beam as it enters the eye and the angle of the light, reflected back from the retina, after it exits the eye. Further work will investigate the validity of such instruments for determining peripheral refraction.
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 03-2019
End Date: 12-2023
Amount: $425,000.00
Funder: Australian Research Council
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