A study of factors affecting the human cone photoreceptor density measured by adaptive optics scanning laser ophthalmoscope

Abstract

To investigate the variation in human cone photoreceptor packing density with various demographic or clinical factors, cone packing density was measured using a Canon prototype adaptive optics scanning laser ophthalmoscope and compared as a function of retinal eccentricity, refractive error, axial length, age, gender, race/ethnicity and ocular dominance. We enrolled 192 eyes of 192 subjects with no ocular pathology. Cone packing density was measured at three different retinal eccentricities (0.5 mm, 1.0 mm, and 1.5 mm from the foveal center) along four meridians. Cone density decreased from 32,200 to 11,600 cells/mm2 with retinal eccentricity (0.5 mm to 1.5 mm from the fovea, P < 0.001). A trend towards a slightly negative correlation was observed between age and density (r = −0.117, P = 0.14). There was, however, a statistically significant negative correlation (r = −0.367, P = 0.003) between axial length and cone density. Gender, ocular dominance, and race/ethnicity were not important determinants of cone density (all, P > 0.05). In addition, to assess the spatial arrangement of the cone mosaics, the nearest-neighbor distances (NNDs) and the Voronoi domains were analyzed. The results of NND and Voronoi analysis were significantly correlated with the variation of the cone density. Average NND and Voronoi area were gradually increased (all, P ≤ 0.001) and the degree of regularity of the cone mosaics was decreased (P ≤ 0.001) with increasing retinal eccentricity. In conclusion, we demonstrated cone packing density decreases as a function of retinal eccentricity and axial length and the results of NND and Voronoi analysis is a useful index for cone mosaics arrangements. The results also serve as a reference for further studies designed to detect or monitor cone photoreceptors in patients with retinal diseases.

Variations in the cone packing density with eccentricity in emmetropes

“…Axial length had a significant role in our study as has been proved by multiple studies 5,8,9 so far. As the axial length increased, the cone count significantly decreased, following the hypothesis of posterior pole being stretched and the cones getting distributed along a larger surface area.…”

“…5,6 Some have a manual addition to the automated software and a few have used special tools with MATLAB software. 5 Lombardo et al 1 have discussed the various technical differences between the Voronoi maps created using images of the photoreceptor mosaic acquired using Variations in cone packing density S Dabir et al different systems, that is, flood-illumination and SLO based. Some of them are due to the differences in the brightness and contrast of the various types of cone mosaics, effect of rods and retinal vessels, and image processing tools.…”

High-Resolution Adaptive Optics Retinal Imaging of Cellular Structure in Choroideremia

“…The technical details of the AOSLO system used for this study have been published previously. 24,25 Wavefront sensing for this system was done using a superluminescent diode at 760 6 5 nm over a 4-mm pupil. Aberration correction was performed using two liquid crystal on silicon spatial light modulators to modulate the phase of the wavefront sensing beacon in two orthogonal polarization directions.…”

Assessment of Different Sampling Methods for Measuring and Representing Macular Cone Density Using Flood-Illuminated Adaptive Optics

“…[27][28][29][30] We used the rtx1 flood-illuminated AO camera from Imagine Eyes to develop a protocol for imaging and sampling cone density from a large macular area in healthy subjects. Previous studies have used the rtx1 to examine retinal diseases, 12,21,22,[31][32][33][34][35][36] study the healthy eye, [37][38][39][40] and optimize AO imaging parameters. 41,42 However, the practicality and limitations of using the rtx1 and other commercial systems have not been well established.…”