Impaired fixation stability in amblyopia cannot be explained by the visual acuity impairment

Abstract

Amblyopia is associated with reduced fixation stability of the amblyopic eye and poorer visual acuity (VA) which is correlated with poorer fixation stability. We investigated whether impaired VA can cause reduced fixation stability. Fixational eye movements were measured in 5 controls and 8 patients with amblyopia (2 strabismics & 6 anisometropes) while fixating a suprathreshold cross (1.2? visual angle at 40cm, 10 × 15 sec blocks per condition). Monocular VA of controls was varied from 20/20 to 20/100 using plus lenses. The amblyopia group completed three monocular conditions; a) amblyopic eye fixating, b) fellow eye fixating and c) fellow eye fixating with VA matched to the amblyopic eye using plus lenses. Fixation stability (quantified using bivariate contour ellipse area) was unaffected by reduced VA in the control group. Amblyopic eyes had significantly poorer fixation stability than fellow eyes as noted in previous studies (1,2). However, such differences did not vary even when VA was matched between the two eyes. Therefore, impaired fixation stability in amblyopic eyes is not simply a result of poor visual acuity.

Meeting abstract presented at the 2016 OSA Fall Vision Meeting

Footnotes

 This work was supported by NSERC to WRB and BT, COETF to RNR.