Retinal pigment epithelial cell count, distribution, and correlations in normal human eyes

To determine the number of the retinal pigment epithelial cells, their regional distribution, and correlations with general variables in normal human eyes.

We examined 53 normal human donor eyes from individuals with a mean age of 58.6 +/- 18.8 years and an axial length of less than 27 mm. After opening the globes by a 16-mm corneoscleral trephination, up to 25 biopsy specimens of the retina and retinal pigment epithelium were obtained in four meridians. The retinal pigment epithelial cells and the retinal photoreceptors were counted on photographs taken from the apical retinal pigment epithelial surface and the inner photoreceptor segments.

Total number of the retinal pigment epithelial cells was 3,556,290 +/- 490,700 (mean +/- S.D.; range, 2,130,500 to 4,653,200), and it was positively correlated with the number of rods and cones, the total area of the retina, the optic disk size, and the retinal pigment epithelial cell density but was independent of gender. The retinal pigment epithelial cell density decreased significantly (P < .001) from the fovea (4,220 +/- 727 cells/mm2) to the midperiphery (3,002 +/- 460 cells/mm2) and to the outer peripheral fundus regions (1,600 +/- 411 cells/mm2). In the retinal periphery, the retinal pigment epithelial cell density was the highest (P < .01) in the nasal fundus region compared with any other fundus quadrant. The retinal pigment epithelial cell density decreased by about 0.3% per year with increasing age.

These data on the quantitative anatomy of the retinal pigment epithelium may be important for physiology and pathophysiology of the visual process, especially in evaluating the effects of aging.