Ultraviolet-B damages corneal endothelium

Direct in vivo observation of acute ultraviolet (UV)-induced corneal endothelial damage is not possible due to the more severe damage produced in the epithelium. In order to quantify damage and evaluate endothelial recovery an indirect method was used. Eyes of pigmented rabbits were irradiated with UV-B (290 to 320 nm) isolated from the output of a high-pressure 1000 W reflectorized Xenon arc lamp by a grating monochromator and appropriate filters. The peak wavelength of the radiation used was 305 nm, with a 18 nm bandwidth at half-maximum. Corneal thickness variations measured with a modified Zeiss (Oberkochen) pachometer were used to follow alterations in epithelial and endothelial function. Epithelial damage alone resulted in a maximum thickness increase of 13.5% within 24 hr with recovery within a further 24 hr. Greater increases in corneal thickness, in the absence of anterior uveal involvement, were taken to indicate endothelial damage, and reached maximum at 2 days, with recovery occurring in 7 days. The threshold for endothelial damage sufficient to disturb corneal deturgescence was 0.12 J X cm-2.