The rhodopsin content of human eyes

To measure the total amount of rhodopsin in human eyes across the life span and to test the hypothesis that the rhodopsin content of infants' and the elderly's eyes is lower than at other ages.

Rhodopsin was extracted from retinal and pigment epithelial fractions of 196 eyes of 102 donors, ages 27 weeks' gestation through 94 years, using quantitative procedures. To recover photopigment bleached by unavoidable light exposure, the fractions from 78 eyes were incubated with 9-cis retinal. The total photopigment (retinal plus pigment epithelial fractions) per eye was examined for significant changes with age, using the higher value from pairs of eyes.

The median rhodopsin content of the higher eye of adults is 6.45 nmoles (range, 3.33-10.84 nmoles) with 8 nmoles or more recovered from 28% of all adult eyes. The rhodopsin content of infants' eyes (< 12 months post-term) is significantly lower than that of older individuals and increases with age. After infancy, no change with age is found. For both infants and adults, 9-cis retinal significantly increases the amount of photopigment recovered without reducing the variance in the amount of photopigment recovered. The rhodopsin content is estimated to be 50% of the median adult amount early in infancy, approximately 5 weeks postterm (95% confidence interval, 0-10 weeks postterm).

A developmental increase in rhodopsin content occurs during infancy. Thereafter rhodopsin content remains constant. The amount of rhodopsin recovered from human eyes is quite variable. Bleaching alone cannot explain the variability.