Cooling effect on excimer laser photorefractive keratectomy

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Purpose To evaluate the effect of cooling on pain, corneal haze, and refractive outcome after excimer laser photorefractive keratectomy (PRK). Setting Tokyo Medical and Dental University Hospital, Tokyo, Japan. Methods The corneal surface was cooled before, during, and after laser ablation using a method called cooling PRK. Thirty-eight highly myopic eyes of 38 patients whose spherical errors ranged from −8.00 to −18.75 diopters (D) were randomized into 2 groups: 16 eyes with conventional PRK and 22 eyes with cooling PRK. Postoperative pain was measured using the Visual Analogue Scale (VAS). Refraction, visual acuity, and complications were followed for up to 2 years. All data were analyzed and compared between groups to evaluate the cooling effect on PRK. Results One day postoperatively, patients in the cooling PRK group had significantly less pain ( P < .01). At 3 months, the haze score in the cooling PRK group was significantly less than in the conventional PRK group ( P < .01). The residual refractive error was not significantly different between the 2 groups until 2 years, when it was greater in the conventional PRK (mean −5.09 D ± 2.11 [SD]) than the cooling PRK group (−4.64 ± 2.27 D). Ten eyes (62.5%) in the conventional PRK group and 15 eyes (68.2%) in the cooling PRK group were within ±1.00 D of the intended refraction. There were no serious complications in the cooling PRK group. Two eyes in the conventional PRK group had severe corneal haze and lost 2 Snellen lines of best corrected visual acuity. Conclusion Corneal cooling on PRK effectively reduced postoperative pain, corneal haze, and myopic regression.