Rigid Gas Permeable Contact Lens Induced Corneal Hypoxia In Rabbit

ABSTRACT

We evaluated the hypoxic effects of the gas permeable contact lens of varying oxygen transmissibilities on the normal rabbit and photorefractive excimer keratectomized cornea. Fifty rabbits were divided into two groups accordig to corneal condition. The first group was thirty normal rabbit group, the other was twenty photorefractive excimer keratectomized group. A month following PRK(photorefractive keratectomy), gas permeable contact lenses were put on both group with three different Dk values (less 60, 60-90,over 120) for 1, 3, 5and 7 days for extended wear. Corneal pathological findings such as abrasion, ulcer were found in proportion to the duration of contact lens wearing in the two groups. Over 4 days continous wearing, the RGP lens was no more tolerable in excimer treated group in consideration of corneal thickness. Gas permeable lens caused an increase in tear LDH activity from 1,190 U/L to 17,000 U/L from the first day in excimer treated group and low DK contact lens group. Light and electron microscopy showed in both group that the longer the wearing time, the more the desqumation of epithelia; these changes were more severe in case of the lens caused the corneal hypoxia and complications and were not tolerable in compromised cornea with excimer laser even in high Dk/L gas permeable contact lens.