Photoreceptor density in dependence of axial length and retinal location in human eyes

Abstract

AbstractPurpose: To examine the density of retinal photoreceptors and retinal pigment epithelium (RPE) cells in relation to myopic axial elongation in human eyes.Methods: Using light microscopy, we counted the density of photoreceptors and RPE cells at the ora serrata, the equator, and at the midpoint between the equator and the posterior pole (MEPP) in enucleated human globes .Results: The study included 78 eyes (mean age: 59.2 ± 15.6 years; range: 32–85 years) with a mean axial length of 27.3 ± 3.6 mm (range: 21.5–37.0 mm). Close to the ora serrata, at the equator and at the MEPP, the photoreceptor and RPE cell density was 11.8 ± 8.8, 29.0 ± 14.3 and 52.3 ± 21.1 cells/48 μm and 27.0 ± 6.6, 21.7 ± 7.2 and 23.4 ± 7.5 cells/480 μm, respectively. Densities of both cell types in all regions measured were positively correlated with each other (all p < 0.001), and decreased with longer axial length (all p < 0.001) and retinal length (all p < 0.001), most marked at the MEPP and least marked close to the ora serrata. Close to the ora serrata, at the equator and at the MEPP, differences between both globe sides in photoreceptor and RPE cell density were 3.98 ± 3.91, 8.93 ± 8.03 and 11.8 ± 11.1 cells/48 μm and 4.67 ± 4.37, 4.27 ± 3.13 and 5.30 ± 4.65 cells/480 μm, respectively. They were not significantly (all p > 0.05) related with axial length and did not differ (all P > 0.05) between both globe sides.Conclusions: The axial elongation‐associated decrease in photoreceptor and RPE cell density is most marked at the MEPP, followed by the equator and finally the ora serrata region. It suggests that the axial elongation‐associated enlargement of the eye wall predominantly takes place in the retro‐equatorial region, followed by the equatorial region. Side differences in cell densities suggest different elongation rates between both sides of the globe.