Nine-Year Results of Excimer Laser Photorefractive Keratectomy for Myopia

Roh, Young Jung; Kim, Man Soo; Kim, Jae Ho

Abstract

PURPOSE: To evaluate the long term stability, complications, and causative factors in eyes that had photorefractive keratectomy (PRK) for myopia.
METHODS
We investigated the results of photorefractive keratectomy (PRK) on 72 consecutive myopic eyes (45 patients) with follow-up of 9 years by using Eximed UV 200LA laser (Summit technology, USA). The patients were divided into two groups according to preoperative myopia : group 1 with diopters between -3.25 D and -6.50 D, group 2 with diopters above -6.50 D. During the follow-up period, 1, 2, 3, 5, 7 and 9 years, refractive error, uncorrected and best corrected visual acuity and corneal opacity were examined. Preoperative myopia ranged from -3.25 D to -9.12 diopters (D), with astigmatism of less than 1.50 D. The excimer laser was set to a maximum correction of -6.50 D at a 5.0mm diameter ablation zone. Patients with more than -6.50 Dmm of myopia had double-pass PRK with two different ablation zone sizes (5.0 and 4.5 mm). The data were analyzed using paird T-test and Regression analysis.
RESULTS
Mean refractive error 9 years after PRK was -2.10+/-0.99 D. It was -1.67+/-0.71 D in moderately myopic eyes (less than 6.50 D) and -2.60+/-1.04 D in highly myopic eyes (more than 7.0 D). The Myopic regression rate markedly decreased after 2years in moderate myopic group but after 3 years in highly myopic group (P<0.01). The most possible causative factor for myopic regression were pre-PRK refraction (P<0.01) and its relative risk was 4.21: At 9 years, 92.3% eyes achieved uncorrected visual acuity of 0.5 or better group1, and 78.7% in group2. Moderate corneal haze was present in 2eyes in group 2.
CONCLUSION
According to these results, we thought that eximer PRK was effective for myopia under -9.62 D. Myopic regression was stabilized after 3 years of PRK.