An acute light and electron microscopic study of ultraviolet 193-nm excimer laser corneal incisions

The 193-nm ultraviolet beam from an argon fluoride excimer laser was focused on the corneas of rabbits to produce incisions of the type necessary for radial keratotomy. The energy densities used were in two ranges, 1.0 to 2.1 J/cm2 per pulse and 200 to 700 mJ/cm2 per pulse. The eyes were enucleated and fixed for histologic and electron microscopic examination immediately after exposure. Structural analysis of the higher energy density exposures showed ridging on the surface of the cornea, micro-pitting on the stromal surface inside the cut, and denudation of the endothelium under the ablation zone. The lower energy density incisions did not exhibit significant surface ridging or endothelial cell loss but did exhibit significant stromal swelling during the laser exposure thus making it difficult to produce incisions of a precisely controlled depth. Beam profile measurements and infrared thermal measurements of the cornea surface during laser exposure were made.