Comparison of photorefractive keratectomy, astigmatic PRK, laser in situ keratomileusis, and astigmatic LASIK in the treatment of myopia.
PURPOSE: To determine factors affecting refractive and visual outcomes in patients treated with astigmatic and spherical photorefractive keratectomy (A-PRK and PRK) and laser in situ keratomileusis (A-LASIK and LASIK). SETTING: University referral refractive surgery clinic. METHODS: Refractive and visual acuity results in 619 eyes of 388 consecutive patients having refractive surgery over a 2-year period by a single surgeon were retrospectively analyzed. Patients were divided into mild-to-moderate myopia (spherical equivalent [SE] less than -6.12 diopters [D]) and high myopia (SE -6.12 D or higher). Multivariate and logistic regression analyses were performed. RESULTS: Refractive results in flap-based and PRK-based procedures were comparable in mild-to-moderate myopia patients but were significantly better in high-myopia patients having flap-based procedures. Refractive stability was greater in flap-based procedures than in PRK-based procedures. Elliptical ablations yielded a marked reduction in the astigmatic cylinder in patients having A-LASIK and A-PRK, while spherical PRK induced small amounts of with-the-rule astigmatism. Complications were uncommon in both groups, consisting primarily of epithelial ingrowth in flap-based procedures and haze in PRK-based procedures. Multivariate regression identified the preoperative SE as a significant determinant of PRK outcomes (with higher success for lower myopia) and intraocular pressure as a minor determinant of outcomes in PRK-based and flap-based procedures. Logistic regression suggested that only the preoperative SE was a significant factor in predicting the likelihood of poor outcomes in PRK patients. CONCLUSIONS: Refractive outcomes were almost identical in patients having elliptical or spherical ablations with flap-based or PRK-based procedures. In eyes with mild-to-moderate myopia, there was little difference in refractive or visual outcomes between flap-based and PRK-based procedures; in eyes with high myopia, flap-based procedures offered more predictable refractive outcomes and better visual outcomes.