NONINVASIVE MEASUREMENT OF CORNEAL EPITHELIAL PERMEABILITY

The Fluorotron Master fluorophotometer was used to measure the corneal epithelial permeability to carboxyfluorescein in the normal unanesthe tized rabbit. This was related to the epithelial fluorescein staining grade as assessed with a slit lamp. The carboxyfluorescein concentrati on in the cornea was measured at 3, 60 and 120 min after bathing the c ornea in 2.7X10(-3) M carboxyfluorescein for 5 min. The epithelial cel l layer permeability was calculated from the corneal carboxyfluorescei n concentration immediately after a balanced salt solution rinse (init ial technique) and from the time zero intercept value extrapolated fro m the 60 and 120 min data (intercept technique). The slit lamp demonst rated 69% of the nonpaired rabbit eyes were free of epithelial defects , whereas, 46% of the paired rabbit eyes were free of defects. Epithel ial permeability values determined from the initial or intercept techn ique were similar (p = 0.77, unpaired 2 tailed t-test for data < 0.165 nm/s). The initial analysis permeability values ranged from 0.0154 to 4.309 nm/s., n = 29. There was a Gaussian distribution of data betwee n 0.015 and 0.144 nm/s with a mean of 0.0646 +/- 0.0070 nm/s. The larg er values correlated with the naturally occurring epithelial defects o bserved with the slit lamp. The epithelial permeability values were in dependent of the contralateral eye or subsequent day measurements.