Centripetal movement of fluorescein dextrans in the cornea: relevance to arcus

The centripetal movement of fluorescein and fluorescein-labelled dextrans (4 to 150 kD) from sclera or cut edge of the cornea was determined in isolated rabbit corneas at 4 and 24 h. Corneas were divided into 5.5 mm diameter central core, inner 5.5 to 8 mm donut, 8 to 12 mm peripheral donut and, where applicable, scleral rim. For all molecules greater than sodium fluorescein (376 D) tracer concentrations in the 5.5 mm core and the 5.5 to 8 mm donut were equal. Without sclera rim, the more central portions of the cornea (5.5 mm core and 5.5 to 8 mm donut) had tracer concentrations equal to those of corneas-with-sclera for all tracers greater than 10 kD. The tracer concentrations in the central cornea were the same in the presence or absence of sclera. The data indicate a physiological barrier to the lateral diffusion of molecules greater than 10 kD between the peripheral and more central cornea.