title: How best to assess suppression in patients with high anisometropia.
abstract: OBJECTIVE
  We have recently described a rapid technique for measuring suppression using a dichoptic signal/noise task. Here, we report a modification of this technique that allows for accurate measurements to be made in amblyopic patients with high levels of anisometropia. This was necessary because aniseikonic image size differences between the two eyes can provide a cue for signal/noise segregation and, therefore, influence suppression measurement in these patients.
  
  
  METHODS
  Suppression was measured using our original technique and with a modified technique whereby the size of the signal and noise elements was randomized across the stimulus to eliminate size differences as a cue for task performance. Eleven patients with anisometropic amblyopia, five with more than 5 diopters (D) spherical equivalent difference (SED), six with less than 5 D SED between the eyes, and 10 control observers completed suppression measurements using both techniques.
  
  
  RESULTS
  Suppression measurements in controls and patients with less than 5 D SED were constant across the two techniques; however, patients with more than 5 D SED showed significantly stronger suppression on the modified technique with randomized element size. Measurements made with the modified technique correlated with the loss of visual acuity in the amblyopic eye and were in good agreement with previous reports using detailed psychophysical measurements.
  
  
  CONCLUSIONS
  The signal/noise technique for measuring suppression can be applied to patients with high levels of anisometropia and aniseikonia if element size is randomized. In addition, deeper suppression is associated with a greater loss of visual acuity in patients with anisometropic amblyopia.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Jinrong
authors.initials: J
authors.lastname: Li
authors.forename: Robert F
authors.initials: RF
authors.lastname: Hess
authors.forename: Lily Y L
authors.initials: LY
authors.lastname: Chan
authors.forename: Daming
authors.initials: D
authors.lastname: Deng
authors.forename: Xiang
authors.initials: X
authors.lastname: Chen
authors.forename: Minbin
authors.initials: M
authors.lastname: Yu
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Thompson
mesh_terms: D000293:Adolescent; D000328:Adult; D015858:Anisometropia / Q000503:physiopathology / Q000628:therapy*; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008297:Male; D012029:Refraction, Ocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult