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  • Title: Photorefractive keratectomy versus laser in situ keratomileusis: comparison of optical side effects. Summit PRK-LASIK Study Group.
    Author: Hersh PS, Steinert RF, Brint SF.
    Journal: Ophthalmology; 2000 May; 107(5):925-33. PubMed ID: 10811085.
    Abstract:
    OBJECTIVE: This report presents patient-reported optical symptoms after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Preoperative and postoperative patient surveys in a prospective, multicenter, randomized clinical trial. PARTICIPANTS: Two hundred twenty eyes of 220 patients entered the study; 105 were randomized to PRK and 115 were randomized to LASIK. INTERVENTION: All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure. Attempted corrections ranged from 6.00 to 15.00 diopters (D). MAIN OUTCOME MEASURES: Glare, halo, and monocular diplopia symptoms as reported by patients on questionnaires before surgery and at the 6-month follow-up. Comparison was made between symptoms when using optical correction before surgery and symptoms without correction after surgery. RESULTS: For both the PRK and LASIK groups analyzed individually, the difference in average glare index before surgery and after surgery was not statistically significant (P = 0.54 for PRK; P = 0.15 for LASIK; t test). Twenty-four PRK patients (41.4%) reported worsening of glare symptoms from baseline compared with 11 LASIK patients (21.6%); however, the difference between the two groups was not statistically significant (P = 0.086, chi-square test). Within the PRK group, the difference in average halo index before and after surgery was statistically significant (P = 0.0003, t test); in the LASIK group, it was not statistically significant (P = 0.1 1, t test). Thirty-four PRK patients (58.6%) reported worsening of halo symptoms from baseline compared with 26 LASIK patients (50.0%); this difference was not statistically significant (P = 0.086, chi-square test). For both the PRK and LASIK groups, the difference in average diplopia index before and after surgery was statistically significant (P < 0.0001 for PRK; 0.047 for LASIK; t test). Twenty-six PRK patients (44.8%) reported a worsening of monocular diplopia symptoms from baseline compared with 19 LASIK patients (35.8%); this difference was not statistically significant (P = 0.39, chi-square test). When changes in glare and halo from before surgery to after surgery were pooled as a glare-halo index, however, the PRK group did show a significantly greater likelihood of demonstrating an increase in symptoms compared with the LASIK group (P = 0.048, chi-square test). CONCLUSIONS: Optical sequelae of glare, halo, and monocular diplopia may occur in some patients after either both PRK or LASIK for moderate to high myopia; in contradistinction, many other patients' preoperative symptoms improve after surgery. On average, PRK patients show an increase in halo and diplopia symptoms, but not glare, after surgery, and LASIK patients show an increase in diplopia, but not glare and halo symptoms. There is a suggestion of a somewhat lesser tendency toward postoperative optical symptoms in LASIK compared with PRK treated eyes.
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