Noninvasive measurement of corneal epithelial permeability

The Fluorotron Master fluorophotometer was used to measure the corneal epithelial permeability to carboxyfluorescein in the normal unanesthetized rabbit. This was related to the epithelial fluorescein staining grade as assessed with a slit lamp. The carboxyfluorescein concentration in the cornea was measured at 3, 60 and 120 min after bathing the cornea in 2.7 x 10(-3) M carboxyfluorescein for 5 min. The epithelial cell layer permeability was calculated from the corneal carboxyfluorescein concentration immediately after a balanced salt solution rinse (initial technique) and from the time zero intercept value extrapolated from the 60 and 120 min data (intercept technique). The slit lamp demonstrated 69% of the nonpaired rabbit eyes were free of epithelial defects, whereas, 46% of the paired rabbit eyes were free of defects. Epithelial permeability values determined from the initial or intercept technique 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 between 0.015 and 0.144 nm/s with a mean of 0.0646 +/- 0.0070 nm/s. The larger values correlated with the naturally occurring epithelial defects observed with the slit lamp. The epithelial permeability values were independent of the contralateral eye or subsequent day measurements.