AGING CHANGES IN THE RETINAL CAPILLARY BED OF THE RAT

Thirty normal albino rats of ages from 2 to 32 months were sacrificed, their globes removed, and their retinas prepared by the pepsin-trypsin digest technique. The mounted preparations were stained with hematoxylin and PAS. The retinal capillaries were then analyzed with a light microscope in the peripapillary, midretinal, and peripheral areas. The following results were obtained: (1) The ratio of endothelial cells to intramural pericytes ranged from 1.57 to 2.18. No definite changes were found between different age groups or between different retinal regions. (2) The number of endothelial cells and intramural pericytes per high-power field decreased with age, with the decrement most marked between 8 and 12 months. (3) Two types of acellular strands were noted: thin, threadlike strands and thick, acellular capillary strands. The number of thin strands per high-power field averaged 4.86, with no obvious increase with aging. The number of thick strands increased markedly between 12 and 24 months: Up to the age of 12 months an average of only 0.02 thick strands were found per high-power field, whereas in rats 24 months or older an average of 0.38 thick strands were found per high-power field. (4) In all age groups the capillary cells appeared more ragged and their nuclei more weakly stained in the periphery than in the other retinal regions; this was more marked in older rats. © 1979.