Thermal consequences of photorefractive keratectomy.
OBJECTIVE
Photorefractive keratectomy (PRK) is still a widely used method for the correction of refractive error despite the advent of laser in situ keratomileusis (LASIK). However, both procedures are associated with significant 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 changes occurring during PRK when performed at different ablation depths.


METHODS
Noncontact, color-coded ocular thermography was performed with an infrared detector apparatus during PRK ablation on 19 ovine corneas. Five different refractive corrections were carried out ranging from -2.00 diopters (D) (ablation depth, 31.2 microm) to -10.00 D (ablation depth, 137.9 microm).


RESULTS
A temperature rise at the corneal surface was demonstrated in all 19 corneas. The mean rise in temperature was 7.35 +/- 1.13 degrees C with a maximum rise in temperature of 8.97 degrees C. A positive correlation was found between the refractive correction and the peak rise in temperature (r2 = 0.57, p< 0.0001). The rate of temperature change was greater for smaller treatments than for larger treatments (r2 = 0.79, p < 0.0001). Corneas undergoing larger treatments were subject to greater rises in temperature for longer periods of time.


CONCLUSIONS
This study suggests that the cornea undergoes a significant rise in temperature as a result of the PRK process. Further investigation is required to determine what effect this thermal loading has on the corneal wound healing response after PRK.
Maldonado-Codina
C
C
Eurolens Research, Department of Optometry and Neuroscience, Manchester, United Kingdom. c.m-codina@umist.ac.uk
Morgan
P B
PB
Efron
N
N
D000818:Animals; D001831:Body Temperature; D003315:Cornea / Q000601:surgery*; D003318:Corneal Opacity / Q000209:etiology; D006358:Hot Temperature / Q000009:adverse effects*; D054018:Lasers, Excimer; D018903:Photorefractive Keratectomy / Q000009:adverse effects*; D054140:Refractive Surgical Procedures; D012756:Sheep; D013817:Thermography; D014945:Wound Healing