Thermal consequences of photorefractive keratectomy

Purpose. Photorefractive keratectomy (PRK) is still a widely used method fo r the correction of refractive error despite the advent of laser in situ ke ratomileusis (LASIK). However, both procedures are associated with signific ant side effects such as corneal haze and regression. Several factors have been implicated in the etiology of haze, one of which is thermal loading of the cornea. The purpose of this study was to investigate the temperature c hanges occurring during PRK when performed at different ablation depths. Me thods. Noncontact, color-coded ocular thermography was performed with an in frared detector apparatus during PRK ablation on 19 ovine corneas. Five dif ferent refractive corrections were carried out ranging from -2.00 diopters (D) (ablation depth, 31.2 mum) to -10.00 D (ablation depth, 137.9 mum) Resu lts. A temperature rise at the corneal surface was demonstrated in all 19 c orneas. The mean rise in temperature was 7.35 +/- 1.13 degreesC with a maxi mum rise in temperature of 8.97 degreesC. A positive correlation was found between the refractive correction and the peak rise in temperature (r(2) = 0.57, p < 0.0001). The rate of temperature change was greater for smaller t reatments than for larger treatments (r(2) = 0.79, P < 0.0001). Corneas und ergoing larger treatments were subject to greater rises in temperature for longer periods of time. Conclusions. This study suggests that the cornea un dergoes a significant rise in temperature as a result of the PRK process. F urther investigation is required to determine what effect this thermal load ing has on the corneal wound healing response after PRK.