Summary
In a total of 400 untreated rats which had achieved ages of up to three years, the age-related morphological changes in the eye, and more particularly in the retina, resulting from three years of artificial lighting were studied. In addition to this, from ten 1067-day old and five 90-day old rats, a total of 9427 measurements of nuclear size were made and the number of nuclei per unit area at the 1st and 2nd retinal neurones were determined.
The most marked morphological changes in the senile rat eye are those shown in the retina: namely a rarefication of the nuclei of the outer nuclear layer of 35.7%±6.1 and of the inner nuclear layer of 26.9%±4.4 with a simultaneous highly significant (p<0.005) age-dependent increase in area of the nuclei of the inner nuclear layer. In one third of the aging animals the retinal capillaris were characterized both by an increase in calibre and in PAS staining, sharper contouring, and thickend walls. There were few signs of age in the choroid. The anterior sections of the bulbus showed a thickening of Descemet's membrane in the cornea by approximately a factor of three in all aging animals, and a sclerosis of the ciliary body and the iris root.
The retinal damage resulting from up to three years of exposure to light intensities of 30, 62 and 223 lux was to a large extent uniform. It was characterized by a general atrophy of the 1st neurone, a partial degeneration of the 2nd neurone and destruction of the retinal structure as well as vascularization of the in part multi-layered pigment epithelium. The influence of the light intensity on the number of damaged retinae was highly significant (p<0.01).
Knowledge of such findings in the rat would appear to be an important factor in long term toxicity studies for differentiating between changes in the eye dependent on age and environment, and those occasioned by the compound being tested.
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Weiße, I., Stötzer, H. & Seitz, R. Age- and light-dependent changes in the rat eye. Virchows Arch. A Path. Anat. and Histol. 362, 145–156 (1974). https://doi.org/10.1007/BF00432392
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DOI: https://doi.org/10.1007/BF00432392