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.
Highlights
The retinal structure of the human eye has been extensively studied
Cone densities measured along the horizontal meridian were higher than along the vertical meridian
This result has been already observed by Garrioch et al (AOSLO) [30], Talcott et al (AOSLO) [31], and Jacob et al [22], who reported a discrepancy of respectively 5.4%, 6% and 8.7%
Summary
The retinal structure of the human eye has been extensively studied. First measurements came from histology where post mortem retinal data were analyzed [1, 2]. The two main devices used to acquire in-vivo images of the retina on a large population are the Adaptive Optics Scanning Laser Ophthalmology (AOSLO) [3,4,5,6,7,8,9,10] and the adaptive optics flood-illumination retinal cameras (e.g. rtx1TM device) [11,12,13,14,15,16,17,18,19,20,21,22]. Both systems used adaptive optics to improve the quality of the images
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