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

Abstract

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.

Three-Dimensional Adaptive Optics–Assisted Visualization of Photoreceptors in Healthy and Pathologically Aged Eyes

“…[40][41][42] The counted cone densities at IS/OS and COST at 2.58 and 6.58 ecc were in agreement with AO-FC/SLO examinations of healthy eyes although these modalities are incapable of separating IS/OS from COST signals and show a mixture of signals from all outer retinal layers. [43][44][45] The oscillation of IS/ OS and COST signals, which were especially visible in our IS/ OS þ COST false-color composite images, were also found with other AO-OCT systems and are most likely a sign of PR segment renewal. 38,39,46 Apart from morphologic factors, technical aspects, such as the wavelength or the type of light source, could contribute to this variation in reflectance properties.…”

Geometry of the Retinal Nerve Fibers From Emmetropia Through to High Myopia at Both the Temporal Raphe and Optic Nerve

“…Adaptive optics retinal imaging studies have shown that, in and around the fovea, axial elongation of the eye in myopia is generally such that the angular spacing between adjacent cone photoreceptors remains constant (i.e., physical density is reduced, consistent with a geometric ''stretch'' of the globe). [31][32][33] Psychophysical measurements of resolution acuity and spatial summation in myopic eyes are consistent with a reduction in retinal ganglion cell density, over and above that implied from such a ''simple'' physical stretch. 34,35 The results of the present study indicate that, in angular units, the geometry of retinal nerve fiber bundles was not differentiable between highly myopic and nonmyopic eyes.…”

“…Mean subject age was 25 years (range, [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and spherical equivalent (SE) ranged from 0D to À13D (minimum 10 subjects per 1D range of refraction between 0D to À5D; 27 subjects in the range À3 to À6D; 17 subjects beyond À6D). Axial length and vitreous chamber depth (VCD) were measured by A-scan ultrasonography (AL-100 biometer; Tomey GmbH, Nürnberg, Germany).…”

Comparative Analysis of Functional and Structural Decline in Retinitis Pigmentosas

“…It is known that the hyperautofluorescent ring manifests as an ellipsoid in the early stages of RP [10], which would imply that there are differences in the lengths of the vertical and horizontal diameters when the disease first becomes evident with SW-AF. Studies using adaptive optics flood illumination have revealed histological and anatomical differences in the photoreceptor distribution between both vertical and horizontal meridians, which may explain the ellipsoid shape of the ring [24,25]. Nevertheless, this ellipsoid has been observed to progressively evolve into a uniformly round shape, which occurs due to a difference in the rate of one ring diameter's constriction compared to that of the other diameter.…”