Axial length and cone density as assessed with adaptive optics in myopia

Dabir, Supriya; Mangalesh, Shwetha; Schouten, Jan S. A. G.; Berendschot, Tos T. J. M.; Kurian, Mathew; Kumar, Anupama Kiran; Yadav, Naresh Kumar; Shetty, Rohit

doi:10.4103/0301-4738.159876

Cited by 16 publications

(11 citation statements)

References 16 publications

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“…In addition to the variability in retinal structure, we also found a large range in axial length across our sample, with longer eyes being associated with lower cone density. Although this trend is in agreement with previous AO literature in the case of the diseased retina, 56 – 58 the relationship between axial length and cone density cannot be attributed to retinal stretching alone. Whereas myopia was considered previously to be one of the defining characteristics of BED, 1 , 3 – 5 many of our subjects were not myopic, having little or no refractive error while still having mosaic disruption; though this was observed in LIAVA, but not LVAVA, subjects.…”

Section: Discussionsupporting

confidence: 92%

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

Patterson

Wilk

Langlo

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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PurposeMutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction.MethodsWe recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family.ResultsThere were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array.ConclusionsOur findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus.

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Section: Discussionsupporting

confidence: 92%

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

Patterson

Wilk

Langlo

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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“…Indeed, even if all experiments show a negative correlation between cone density (cone/mm 2 ) and axial length, the level of correlation (i.e. r 2 ) differs remarkably, it ranged from 0.14 [ 8 ] or 0.16 [ 19 ] to 0.40 [ 23 ] or 0.56 [ 5 ] at an eccentricity of 2° or 3° and even 0.75 [ 6 ] at 1° of eccentricity.…”

Section: Discussionmentioning

confidence: 99%

“…Another example is the role of the axial length (AL) on cone density expressed in metric units that should be clarified. Indeed, some authors found an important correlation (r 2 = 0.56 at 3°, 0.37 at 5° and 0.23 at 7° [ 5 ]; r 2 = 0.40 at 2° [ 23 ]; r 2 = 0.75 at 1° [ 6 ]) while others found low correlation (r 2 = 0.14 at ~2°, 0.022 at 3° and 0.037 at 5° [ 8 ]; r 2 = 0.16 at 2° and 0.14 at 3° [ 19 ]).…”

Section: Introductionmentioning

confidence: 99%

Distribution of cone density, spacing and arrangement in adult healthy retinas with adaptive optics flood illumination

2018

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The aim of this article is to analyse cone density, spacing and arrangement using an adaptive optics flood illumination retina camera (rtx1™) on a healthy population. Cone density, cone spacing and packing arrangements were measured on the right retinas of 109 subjects at 2°, 3°, 4°, 5° and 6° of eccentricity along 4 meridians. The effects of eccentricity, meridian, axial length, spherical equivalent, gender and age were evaluated. Cone density decreased on average from 28 884 ± 3 692 cones/mm2, at 2° of eccentricity, to 15 843 ± 1 598 cones/mm2 at 6°. A strong inter-individual variation, especially at 2°, was observed. No important difference of cone density was observed between the nasal and temporal meridians or between the superior and inferior meridians. However, the horizontal and vertical meridians differed by around 14% (T-test, p<0.0001). Cone density, expressed in units of area, decreased as a function of axial length (r2 = 0.60), but remained constant (r2 = 0.05) when cone density is expressed in terms of visual angle supporting the hypothesis that the retina is stretched during the elongation of the eyeball. Gender did not modify the cone distribution. Cone density was slightly modified by age but only at 2°. The older group showed a smaller density (7%). Cone spacing increased from 6,49 ± 0,42 μm to 8,72 ± 0,45 μm respectively between 2° and 6° of eccentricity. The mosaic of the retina is mainly triangularly arranged (i.e. cells with 5 to 7 neighbors) from 2° to 6°. Around half of the cells had 6 neighbors.

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“…Whilst the optical refractive error of myopia can be corrected using spectacles or contact lenses, the axial elongation of the myopic eye can markedly increase the risk of sight-threatening conditions such as retinal detachment 1 , glaucoma 2 , and myopic macular degeneration 3 . In the absence of such pathological processes it has also been demonstrated that the globe elongation that occurs in myopia can lead to secondary peripheral retinal thinning 4 – 6 , in addition to a reduction in the density of both photoreceptors 7 – 9 and retinal ganglion cells (RGCs) 10 , 11 .…”

Section: Introductionmentioning

confidence: 99%

Altered spatial summation optimizes visual function in axial myopia

Stapley

Anderson

Saunders

et al. 2020

Sci Rep

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This study demonstrates significant differences between the area of complete spatial summation (Ricco's area, RA) in eyes with and without non-pathological, axial myopia. Contrast thresholds were measured for six stimuli (0.01-2.07 deg 2) presented at 10º eccentricity in 24 myopic subjects and 20 age-similar non-myopic controls, with RA estimated using iterative two-phase regression analysis. To explore the effects of axial length-induced variations in retinal image size (RIS) on the measurement of RA, refractive error was separately corrected with (i) trial lenses at the anterior focal point (near constant inter-participant RIS in mm), and (ii) contact lenses (RIS changed with axial length). For spectacle corrected measurements, RA was significantly larger in the myopic group, with a significant positive correlation also being observed between RA and measures of co-localised peripheral ocular length. With contact lens correction, there was no significant difference in RA between the groups and no relationship with peripheral ocular length. The results suggest RA changes with axial elongation in myopia to compensate for reduced retinal ganglion cell density. furthermore, as these changes are only observed when axial length induced variations in RIS are accounted for, they may reflect a functional adaptation of the axially-myopic visual system to an enlarged RIS. Myopia is a common refractive condition, whereby the axial length of the globe is too great for its optical power. Whilst the optical refractive error of myopia can be corrected using spectacles or contact lenses, the axial elongation of the myopic eye can markedly increase the risk of sight-threatening conditions such as retinal detachment 1 , glaucoma 2 , and myopic macular degeneration 3. In the absence of such pathological processes it has also been demonstrated that the globe elongation that occurs in myopia can lead to secondary peripheral retinal thinning 4-6 , in addition to a reduction in the density of both photoreceptors 7-9 and retinal ganglion cells (RGCs) 10,11. Deficits in visual function have also been reported in the myopic, but otherwise healthy, visual system. Numerous studies have objectively investigated retinal function in myopia through measurement of standard electroretinograms (ERG) 12,13 pattern ERG 14 and multifocal ERG 4,13,15. These studies have revealed altered responses in myopes, including reductions in amplitude 12-14 and longer implicit times 4,13,15. Other studies have reported reductions in function when examined using clinical tests of visual acuity 16,17 , peripheral resolution acuity 4,18,19 , and contrast sensitivity 20. It may be hypothesized that changes in visual function observed in non-pathological myopia may be accounted for by reductions in the local density of retinal neurons (e.g., RGCs) and corresponding alterations in the basic visual process of spatial summation. This refers to the ability of visual system to integrate light energy over area and serves to maximize the detection of a signal in the presenc...

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Axial length and cone density as assessed with adaptive optics in myopia

Cited by 16 publications

References 16 publications

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

Distribution of cone density, spacing and arrangement in adult healthy retinas with adaptive optics flood illumination

Altered spatial summation optimizes visual function in axial myopia

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