Changes in corneal autofluorescence and corneal epithelial barrier function with aging.

Corneal epithelial permeability studies using fluorophotometers were performed on 90 eyes of 51 normal subjects. After recording the autofluorescence of the cornea (AFC) and of the lens (AFL), we applied 20 microliters of 2% sodium fluorescein to the conjunctival sac. The corneal fluorescence 45 min later (F45), which paralleled the corneal epithelial permeability to fluorescein, was measured by fluorophotometer and analyzed. All parameters of the two eyes of each subject correlated well with each other. There was positive correlation between AFL and patient age and between AFC and patient age (r = 0.78, p < 0.001, and r = 0.74, p < 0.001, respectively). The F45 increased exponentially with advancing age (r = 0.67, p < 0.001). The strong correlation between AFC and AFL in each eye (r = 0.79, p < 0.001) indicated corresponding aging processes in both the cornea and the lens. The increase in epithelial permeability with age possibly represents a subclinical breakdown of barrier function, rendering the corneas more vulnerable to insults.