Effect of preoperative tear function on early functional visual acuity after laser in situ keratomileusis

Purpose: To assess the effect of preoperative tear function on early changes in functional visual acuity (FVA) after laser in situ keratomileusis (LASIK). Setting: Minamiaoyama Eye Clinic, Tokyo, Japan. Methods: This prospective single-center study assessed the effect of preoperative and postoperative tear functions on FVA in 30 eyes of 15 patients who had LASIK. Functional visual acuity was defined as the binocular recognition acuity measured by the FVA tester (Wellsystem) during a 10-second, blink-free period. All patients had a Schirmer test with anesthesia and tear-film breakup time (BUT) measurements preoperatively and 1 day and 1 week after LASIK. Corneal topography and Landolt visual acuity and FVA measurements were performed before surgery and 1 day and 1 week after LASIK. Eyes with a Schirmer test reading less than 5.0 mm and a BUT less than 5 seconds were grouped as definite dry eye (DDE). Eyes with a normal Schirmer test score but a shortened BUT were grouped as probable dry eye (PDE). Results: In all patients, the best uncorrected Landolt visual acuity was 20/20 or better at the postoperative examination times. In the DDE group, the mean preoperative FVA declined from 1.2 to 0.75 ± 0.16 (SD) at 1 day and increased to 1.2 at 1 week. No change in FVA was observed postoperatively in the PDE group. Conclusion: Laser in situ keratomileusis patients with low basal tearing and full uncorrected distance Landolt acuity may experience a transient decrease in FVA that returns to baseline within 1 week.