title: The effect of LASIK on best-corrected high-and low-contrast visual acuity.
abstract: OBJECTIVE
  To evaluate the effects of laser in situ keratomileusis (LASIK) and LASIK with concurrent astigmatic keratectomy (LASIK/AK) on high- and low-contrast visual acuity.
  
  
  METHODS
  The setting was a university refractive surgery practice. Patients were recruited from those undergoing LASIK or LASIK/AK for myopia (>1.00 D spherical equivalent) between May 1996 and August 1997. All subjects were at least 21 years of age. Testing occurred preoperatively and 3 and 6 months after LASIK. Main outcome measures were best spectacle-corrected, high- and low-contrast visual acuity.
  
  
  RESULTS
  For all subjects, there was a significant effect of surgery on nondilated low-contrast visual acuity (repeated measures two-way analysis of variance, p < 0.0001). Tukey's posthoc analysis showed that preoperative low-contrast visual acuity scores were significantly different from 3-month [0.08 logarithm of the minimum angle of resolution (logMAR)] and 6-month (0.11 logMAR) scores for patients undergoing LASIK and LASIK/AK. Under dilated conditions, there was a significant effect of surgery for high- and low-contrast visual acuity (analysis of variance, p < 0.0001 for both). Only changes in low-contrast visual acuity were clinically meaningful [LASIK, visual acuity reduction of 0.1 logMAR (1 line); LASIK/AK, visual acuity reduction of 0.15 logMAR (1.5 lines)]. When considering high and low myopes separately (LASIK only), the level of myopia had a significant effect on the visual acuity after surgery (analysis of variance, p = 0.01). Preoperative, dilated, low-contrast visual acuity scores for high myopes were significantly different from 3-month (0.14 logMAR) and 6-month (0.13 logMAR) scores. No differences were noted for low myopes.
  
  
  CONCLUSIONS
  Clinically meaningful postoperative changes in low-contrast visual acuity were noted in patients undergoing LASIK and LASIK/AK under natural and dilated conditions. Postoperative, dilated, low-contrast visual acuity scores were significantly worse than preoperative scores for high myopes, but remained unchanged for low myopes.
authors.affiliation: The Ohio State University, College of Optometry, Columbus, Ohio 43210, USA.
authors.forename: Melissa D
authors.initials: MD
authors.lastname: Bailey
authors.forename: Michael D
authors.initials: MD
authors.lastname: Olson
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bullimore
authors.forename: Lisa
authors.initials: L
authors.lastname: Jones
authors.forename: Robert K
authors.initials: RK
authors.lastname: Maloney
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D015350:Contrast Sensitivity / Q000502:physiology; D003315:Cornea / Q000601:surgery; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D009799:Ocular Physiological Phenomena; D011446:Prospective Studies; D014792:Visual Acuity / Q000502:physiology*