Human corneal endothelial permeability to fluorescein and fluorescein glucuronide

Abstract

The corneal endothelial permeability coefficient (P(ac)) for fluorescein and fluorescein glucuronide was determined in ten normal young volunteers. After oral administration of fluorescein, the apparent concentrations of both dyes in the corneal stroma and the anterior chamber were measured by differential fluorometry. The apparent dye levels calculated directly from the in vivo fluorometric measurements were converted to the true ones, based on the result of a normalization experiment performed in rabbit eyes. The value of P(ac) averaged 5.44 ± 1.77 x 10-4 cm/min for fluorescein and 3.77 ± 1.10 x 10-4 cm/min for fluorescein glucuronide (mean ± SD,N=20); the former was significantly greater than the latter (paired t-test, P<0.001). The aqueous-cornea distribution ratio was 0.50 ± 0.14 for fluorescein and 0.66 ± 0.16 for fluorescein glucuronide; the latter was significantly greater than the former (paired t-test, P<0.001). It was suggested that the previously reported values of P(ac) for fluorescein in the human eye were underestimates.