title: Pattern-related visual stress, chromaticity, and accommodation.
abstract: OBJECTIVE
  To investigate the impact of colored overlays on the accommodative response of individuals, with and without pattern-related visual stress (PRVS), a condition in which individuals manifest symptoms of perceptual distortion and discomfort when viewing a 3-cyc/deg square-wave grating.
  
  
  METHODS
  Under double-masked conditions, 11 individuals who reported PRVS selected an overlay with a color individually chosen to reduce perceptual distortion of text and maximize comfort (PRVS group). Two groups of control subjects individually matched for age, sex, and refractive error were recruited. Control group 1 similarly chose an overlay to maximize comfort. Control group 2 used the same overlays as the paired PRVS participant. The overlay improved reading speed by 10% (P < 0.001), but only in the PRVS group. A remote eccentric photorefractor was used to record accommodative lag while participants viewed a cross on a background. The background was uniform or contained a grating and was either gray or had a chromaticity identical with that of the chosen overlay. There were therefore four backgrounds in all.
  
  
  RESULTS
  Overall, the accommodative lag was 0.44 D greater in the participants with PRVS. When the background had the chosen chromaticity, the accommodative lag was reduced by an average of 0.16 D (P = 0.03) in the PRVS group, but not in the symptom-free groups: in control group 2 the colored background slightly increased the accommodative lag.
  
  
  CONCLUSIONS
  Accommodative lag was greater in individuals susceptible to pattern-related visual stress and was reduced by a colored background.
authors.affiliation: Vision and Eye Research Unit, Postgraduate Medical Institute, Cambridge, United Kingdom; peter.allen@anglia.ac.uk
authors.forename: Peter M
authors.initials: PM
authors.lastname: Allen
authors.forename: Atif
authors.initials: A
authors.lastname: Hussain
authors.forename: Claire
authors.initials: C
authors.lastname: Usherwood
authors.forename: Arnold J
authors.initials: AJ
authors.lastname: Wilkins
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D055253:Color Vision / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D010468:Perceptual Disorders / Q000503:physiopathology*; D012029:Refraction, Ocular / Q000502:physiology; D013312:Stress, Physiological; D014787:Vision Tests; D055815:Young Adult