Abstract
Purpose: :
The acute corneal reponse to solar UV rays, photokeratitis, is caused by UVB rays. The damage of the cornea disturbs the normal corneal deturgescence mechanisms by which the cornea maintains normal hydration and transparency; the hydration, transparency and light absorption of the cornea are changed. The purpose of this study was to examine whether UVB doses (corresponding to 2.5 or 5 hours UVB exposure of the human cornea to UVB rays from sunlight) applied on the rabbit cornea evoke changes in corneal optics as evaluated by changes in corneal hydration and light absorption.
Methods: :
Rabbit corneas were irradiated with a daily UVB dose of 0.25 J/cm2 or 0.5 J/cm2 for four days. One day after finishing the irradiations the rabbits were sacrificed and corneal light absorption measured using our spectrophotometrical method described previously. Corneal hydration was examined using an ultrasonic Pachymeter every day before the irradiation procedures and the last day before the sacrificing the animals.
Results: :
Changes in corneal optics appeared after the repeated exposure of the cornea to a UVB dose of 0.25 J/cm2 and massively increased after the repeated exposure of the cornea to a UVB dose of 0.5 J/cm2. The first significant changes in corneal hydration appeared already after a single exposure of the cornea to a UVB dose of 0.25 J/cm2.
Conclusions: :
Changes in corneal hydration appeared after the exposure of the rabbit cornea to a single UVB dose equivalent to 2.5 hours of solar UVB radiation reaching the human cornea from sunlight. Repeated exposure of the rabbit cornea to same UVB dose evoked profound changes in the corneal optics. The results point to the danger for the human eye from even a short stay in sunlight.
Keywords: cornea: stroma and keratocytes • inflammation • radiation damage: light/UV