title: Mesopic contrast sensitivity function after laser in situ keratomileusis.
abstract: OBJECTIVE
  To evaluate contrast sensitivity under mesopic conditions in patients who have undergone uncomplicated bilateral laser in situ keratomileusis (LASIK) for myopia.
  
  
  METHODS
  Best-corrected monocular contrast sensitivity was measured with the Stereo Optical F.A.C.T. chart at 1.5, 3, 6, 12, and 18 c/deg in 20 patients (20 left eyes) before and after bilateral LASIK (with the Nidek EC-5000 excimer laser and the Automated Corneal Shaper). Mean preoperative refractive error was -6.40 +/- 1.28 D (range -4.00 to -8.00 D) and postoperative mean refractive error was -0.41 +/- 0.45 D (range -0.75 to +0.50 D). Contrast sensitivity function was measured before and 6 months after surgery using four different chart luminances: 85, 5, 2.5, and 0.1 cd/m2, the first being a photopic level and the rest mesopic. Log contrast sensitivity values at each spatial frequency were used for statistical analysis and normalized values for graphical representation.
  
  
  RESULTS
  Contrast sensitivity of postoperative LASIK eyes did not differ from preoperative values at a photopic level (85 cd/m2). However, under mesopic conditions (5 cd/m2 or less) a statistically significant reduction (P<.01) in contrast sensitivity was found at high spatial frequencies (12 and 18 c/deg), although no significant contrast sensitivity differences were observed at low and middle spatial frequencies (P>.01 for 1.5, 3 and 6 c/deg).
  
  
  CONCLUSIONS
  LASIK induced significant reductions in contrast sensitivity under mesopic conditions only at high spatial frequencies, even though the photopic contrast sensitivity function was normal.
authors.affiliation: Unitat d'Optometria i Ciències de la Visió, Universitat de Valencia, Spain. roberto.montes@uv.es
authors.forename: Robert
authors.initials: R
authors.lastname: Montés-Micó
authors.forename: Enrique
authors.initials: E
authors.lastname: España
authors.forename: Jose L
authors.initials: JL
authors.lastname: Menezo
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008027:Light; D008297:Male; D009216:Myopia / Q000503:physiopathology* / Q000601:surgery*