title: Efficacy of measuring visual performance of LASIK patients under photopic and mesopic conditions.
abstract: BACKGROUND
  The aim of the study was to compare the visual performance of LASIK eyes measured using high-contrast logMAR letter charts under bright (photopic) and dim (mesopic) conditions.
  
  
  METHODS
  A total of 46 subjects (35 +/- 8 years of age) undergoing LASIK procedures were recruited for the study. The best spectacle-corrected visual acuity (BSCVA) of each subject was measured using the high-contrast ETDRS logMAR chart under photopic and mesopic conditions at 3 visits: preoperative (Pre), 1 month postoperative (Post1) and 3 months postoperative (Post3). The differences in logMAR scores for the right eyes only were analysed for the Pre-Post1 (n = 46), Pre-Post3 (n = 18) and Post1-Post3 (n = 16) comparisons.
  
  
  RESULTS
  The logMAR scores of subjects were worse at the 1-month postoperative visit than preoperatively, and improvement in visual performance was seen at the 3-month postoperative visit. These changes in visual performance became more evident under mesopic conditions. The means and standard errors of the differences in logMAR scores for the Pre-Post3 (0.097 +/- 0.020) were slightly larger than those of the Pre-Post1 (-0.067 +/- 0.019) and Post1-Post3 (0.031 +/- 0.012) comparisons. Under mesopic conditions, the visual performance of the subjects was statistically significant for the 3 comparisons, but not under photopic conditions.
  
  
  CONCLUSIONS
  High-contrast logMAR chart performed under mesopic conditions has the potential to replace visual acuity measured under photopic conditions in providing more reliable representation of postoperative visual outcomes of LASIK eyes. Eye doctors should consider performing this vision test routinely to gauge the success of LASIK surgery.
authors.affiliation: Singapore Polytechnic Optometry Centre. Wilfred_Tang@sp.edu.sg
authors.forename: Wilfred
authors.initials: W
authors.lastname: Tang
authors.forename: Wee-Jin
authors.initials: WJ
authors.lastname: Heng
authors.forename: Hung-Ming
authors.initials: HM
authors.lastname: Lee
authors.forename: Han-Bor
authors.initials: HB
authors.lastname: Fam
authors.forename: Nai-Shin
authors.initials: NS
authors.lastname: Lai
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects; D008029:Lighting; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology; D014787:Vision Tests / Q000379:methods*; D014792:Visual Acuity