THE EFFECT OF CORNEAL EDEMA UPON EXCIMER LASER ABLATION

Chris Fields

Abstract

Excimer laser photorefractive keratectomy (PRK) is a promising technique for altering myopic refractive error which is currently in FDA trials. PRK has been reasonably successful in other parts of the world where it is used more extensively than in the USA even though there have been some reports of corneal haze and regression of correction for deeper ablations. The mechanisms responsible for these unwanted side effects remain incompletely understood. This is a study of the effect of corneal hydration which could affect PRK ablation rate thereby potentially altering the accuracy and clarity of the result. Freshly slaughtered pig eyes and the eyes of Dutch Belted rabbits (in-vivo) were de-epithelialized with a knife. 3.0 - 4.5 mm central ablation zones were produced using a 193 nm ArF ophthalmic excimer laser. Ablation was performed either immediately or after a 15 minute incubation period in distilled water as a means of inducing corneal edema. The smoothness of the ablated surface was evaluated using specular reflection microscopy with photodocumentation. At shallow ablation depths (12.5 u) experimental and control surfaces appeared quite similar. At greater ablation depths (37.5 and 62.5 u) the edematous surface was increasingly less regular in comparison to the non-edematous samples. This result indicates the need to monitor the immediately pre-operative cornea for the development of edema between the time the epithelium is removed and the ablation performed, particularly if there is any delay in performing the ablation.

Details

Year: 1992

Program Number: Poster 29

Author Affiliation: n/a

Co-Authors: Stephen Taylor, Felix Barker

Co-Author Affiliation: n/a

Room: Great Hall