The incidence and risk factors for developing dry eye after myopic LASIK

PURPOSE: To determine the incidence of dry eye and its risk factors after myopic laser-assisted in situ keratomileusis (LASIK). DESIGN: Single-center, prospective randomized clinical trial of 35 adult patients, aged 24 to 54 years, with myopia undergoing LASIK. METHODS: SETTING AND STUDY POPULATION: Participants were randomized to undergo LASIK with a superior or a nasal hinge flap. They were evaluated at 1 week and 1, 3, and 6 months after surgery. INTERVENTION: Bilateral LASIK with either a superior,hinge Hansatome microkeratome (n = 17) or a nasal-hinge Amadeus microkeratome (n = 18). MAIN OUTCOME MEASURES: The criterion for dry eye was a total corneal fluorescein staining score >= 3. Visual acuity, ocular surface parameters, and corneal sensitivity were also analyzed. Cox proportional-hazard regression was used to assess rate ratios (RRs) with 95% confidence intervals. RESULTS: The incidence of dry eye in the nasal, and superior-hinge group was eight (47-06%) of 17 and nine (52.94%) of 17 at 1 week, seven (38.89%) of 18 and seven (41-18%) of 17 at I month, four (25%) of 16 and three (17.65%) of 17 at 3 months, and two (12.50%) of 16 and six (35.29%) of 17 at 6 months, respectively. Dry eye was associated with level of preoperative myopia (RR 0.88/each diopter, P =.04), laser-calculated ablation depth (RR 1.01/lLm, P = 0.01), and combined ablation depth and flap thickness (RR 1.01/mu m, P = 0.01). CONCLUSIONS: Dry eye occurs commonly after LASIK surgery in patients with no history of dry eye. The risk of developing dry eye is correlated with the degree of preoperative myopia and the depth of laser treatment.