Cone photoreceptor definition on adaptive optics retinal imaging

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Abstract

Aims

To quantitatively analyse cone photoreceptor matrices on images captured on an adaptive optics (AO) camera and assess their correlation to well-established parameters in the retinal histology literature.

Methods

High resolution retinal images were acquired from 10 healthy subjects, aged 20–35 years old, using an AO camera (rtx1, Imagine Eyes, France). Left eye images were captured at 5° of retinal eccentricity, temporal to the fovea for consistency. In three subjects, images were also acquired at 0, 2, 3, 5 and 7° retinal eccentricities. Cone photoreceptor density was calculated following manual and automated counting. Inter-photoreceptor distance was also calculated. Voronoi domain and power spectrum analyses were performed for all images.

Results

At 5° eccentricity, the cone density (cones/mm ² mean±SD) was 15.3±1.4×10 ³ (automated) and 13.9±1.0×10 ³ (manual) and the mean inter-photoreceptor distance was 8.6±0.4 μm. Cone density decreased and inter-photoreceptor distance increased with increasing retinal eccentricity from 2 to 7°. A regular hexagonal cone photoreceptor mosaic pattern was seen at 2, 3 and 5° of retinal eccentricity.

Conclusions

Imaging data acquired from the AO camera match cone density, intercone distance and show the known features of cone photoreceptor distribution in the pericentral retina as reported by histology, namely, decreasing density values from 2 to 7° of eccentricity and the hexagonal packing arrangement. This confirms that AO flood imaging provides reliable estimates of pericentral cone photoreceptor distribution in normal subjects.

Related collections

Most cited references 23

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The arrangement of the three cone classes in the living human eye.

A Roorda, D R Williams (1999)

Human colour vision depends on three classes of receptor, the short- (S), medium- (M), and long- (L) wavelength-sensitive cones. These cone classes are interleaved in a single mosaic so that, at each point in the retina, only a single class of cone samples the retinal image. As a consequence, observers with normal trichromatic colour vision are necessarily colour blind on a local spatial scale. The limits this places on vision depend on the relative numbers and arrangement of cones. Although the topography of human S cones is known, the human L- and M-cone submosaics have resisted analysis. Adaptive optics, a technique used to overcome blur in ground-based telescopes, can also overcome blur in the eye, allowing the sharpest images ever taken of the living retina. Here we combine adaptive optics and retinal densitometry to obtain what are, to our knowledge, the first images of the arrangement of S, M and L cones in the living human eye. The proportion of L to M cones is strikingly different in two male subjects, each of whom has normal colour vision. The mosaics of both subjects have large patches in which either M or L cones are missing. This arrangement reduces the eye's ability to recover colour variations of high spatial frequency in the environment but may improve the recovery of luminance variations of high spatial frequency.

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Aging of the human retina. Differential loss of neurons and retinal pigment epithelial cells.

Joe G. Hollyfield, Sean Gao (1991)

The impact of aging on cell loss in the human retina was examined in foveal and temporal equatorial regions in eyes from 35 donors with ages spanning a 78-yr period from the second to the ninth decade of life. Equatorial cones and retinal pigment epithelial cells (RPE) decreased at uniform rates from the second to the ninth decade, 16 and 14 cells/mm2/yr, respectively. Equatorial rods and cells in the ganglion cell layer (GCL) showed nonuniform rate decreases with age. The rates of rod and GCL cell loss were faster between the second and fourth decades (970 and 9 cells/mm2/yr, respectively) than between the fourth and ninth decades (570-330 and 6-3 cells/mm2/yr). The rod and GCL cell densities at the temporal equator maintained a constant ratio (rods-GCL cell ratio = 103 +/- 0.4, mean +/- standard deviation) and the same reduction slope ratio at different times during aging. Thus, the equatorial rod and GCL cell losses were correlated statistically. The ratio of equatorial photoreceptors to RPE cells showed no significant change with age, suggesting parallel loss of these closely apposed cells. At the foveal center, the variability of cone density between individuals in each decade grouping was large (1.7- to threefold). No significant differences were found in cone or RPE cell densities at the foveal center from the second to ninth decade, suggesting that the densities of foveal cones and RPE cells were stable throughout this period. Foveal RPE density was significantly higher than equatorial RPE density in each age group. No significant difference was found between the equatorial photoreceptor-RPE ratio and foveal cone-RPE ratio in any age group. Cells in the GCL in the fovea decreased by approximately 16% from the second to the sixth decade. These results indicated that (1) rod photoreceptors and cells in the GCL were more vulnerable to loss during aging than cones; (2) photoreceptors and RPE cells showed parallel changes during aging; and (3) the photoreceptor loss accompanying aging was less pronounced in the fovea than in the peripheral retina.

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Supernormal vision and high-resolution retinal imaging through adaptive optics.

Richard Miller, J.-Q. Liang, Ashley R. Williams (1997)

Even when corrected with the best spectacles or contact lenses, normal human eyes still suffer from monochromatic aberrations that blur vision when the pupil is large. We have successfully corrected these aberrations using adaptive optics, providing normal eyes with supernormal optical quality. Contrast sensitivity to fine spatial patterns was increased when observers viewed stimuli through adaptive optics. The eye's aberrations also limit the resolution of images of the retina, a limit that has existed since the invention of the ophthalmoscope. We have constructed a fundus camera equipped with adaptive optics that provides unprecedented resolution, allowing the imaging of microscopic structures the size of single cells in the living human retina.

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Author and article information

Journal

Journal ID (nlm-ta): Br J Ophthalmol

Journal ID (iso-abbrev): Br J Ophthalmol

Journal ID (hwp): bjophthalmol

Journal ID (publisher-id): bjo

Title: The British Journal of Ophthalmology

Publisher: BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )

ISSN (Print): 0007-1161

ISSN (Electronic): 1468-2079

Publication date (Print): August 2014

Publication date (Electronic): 11 April 2014

Volume: 98

Issue: 8

Pages: 1073-1079

Affiliations

[1 ]National Institute for Health Research, Biomedical Research Centre for Ophthalmology , London, UK

[2 ]Moorfields Eye Hospital , London, UK

[3 ]Division of Cellular Therapy, UCL Institute of Ophthalmology , London, UK

[4 ]Centre for Ophthalmology and Visual Science (incorporating Lions Eye Institute), The University of Western Australia , Perth, Australia

[5 ]Department of Research and Development, The Reading Centre, Moorfields Eye Hospital , London, UK

Author notes

[Correspondence to ] Dr Manickam Nick Muthiah, Vitreoretinal Research, Moorfields Eye Hospital, 162 City Road, London EC1V 2PD, UK; drnickmuthiah@ 123456gmail.com

MNM and CG contributed equally.

Article

Publisher ID: bjophthalmol-2013-304615

DOI: 10.1136/bjophthalmol-2013-304615

PMC ID: 4112439

PubMed ID: 24729030

SO-VID: 69ef6a57-4d4c-4a4c-b8df-2dfcf1c4e3e6

License:

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/3.0/