This investigation was directed at determining the count and regional distribution of photoreceptors in the eyes of 21 human cornea donors aged between 2 and 90 years. Mean count of rods was 60,123,000 +/- 12,907,000, and mean cone count was 3,173,000 +/- 555,000. Determined 40 microns away from the foveola, cone density measured 125,500 cones/mm2. Extrapolating the distribution curve, cone concentration in the foveal center can be assumed to be about 150,000 cells/mm2 to 180,000 cones/mm2. Towards the retinal periphery, cone density decreased from 6000 cones/mm2 at a distance of 1.5 mm from the fovea to 2500 cells/mm2 close to the ora serrata. Comparing different fundus regions, cone concentration was significantly highest in the nasal region. Cone diameter increased from the center towards the periphery. At a distance of 40 microns away from the foveola, it measured about 3.3 microns, and in the outer retinal regions about 10 microns. Rod density was highest in a ring-like area at a distance of about 3-5 mm from the foveola with a mean of 72,246 +/- 17,295 cells/mm2. Rod density peaked at 150,000 rods/mm2. It decreased towards the retinal periphery to 30,000-40,000 rods/mm2. Rod diameter increased from 3 microns at the area with the highest rod density to 5.5 microns in the periphery. The hexagonal rod and cone inner segments were regularly arranged in a honey-comb fashion.
The optic nerve head in highly myopic eyes is distinctly different from normal optic disks. We performed magnification-corrected morphometry of photographs of 51 optic nerve heads in highly myopic eyes (myopic refraction of more than -8.00 diopters). Mean refraction was -15.49 +/- 5.76 diopters (range, -8.00 to 28.00 diopters), mean age 63.0 +/- 12.1 years (range, 27-87 years). The disks were significantly (P less than 0.000001; Wilcoxon-Mann-Whitney test) larger and more ovally configurated than 457 unselected normal optic nerve heads with a myopic refraction of less than -8.00 diopters. Refraction, size of the disk, and area of the parapapillary region with chorioretinal atrophy were significantly (P less than 0.00001) correlated with each other. The parapapillary vessel diameter was independent from the disk size. Highly myopic disks can be regarded as secondary acquired macrodisks, the size of which is correlated with refraction and possibly age. They should be differentiated from secondary, acquired macrodisks in congenital glaucoma and from primary macrodisks. As in normal eyes, the parapapillary vessel caliber can be used to estimate the optic disk size in relative and approximately absolute units.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.