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jing liu, Jinrong Li, Zidong Chen, Xiaoxiao Cai, Junpeng Yuan, Daming Deng, Minbin Yu; Interocular differences in size perception of black-white figure ground asymmetries in anisometropic amblyopia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3090.
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© ARVO (1962-2015); The Authors (2016-present)
Interocular difference of size perception (aniseikonia) is common in anisometropia. For those with normal vision, the perceived size of targets can also be influenced by various factors. It has previously been shown that a target on a black background can appear larger than one on a white background (Kremkow, PNAS, 2014). Here, we describe a novel computer-based aniseikonia test using variable contrast polarities at different interocular contrast levels. A comprehensive evaluation of aniseikonia in anisometropic amblyopia was compared to normal individuals.
Fifteen normal participants [Spherical Equivalent Refraction (SER):-0.16±0.46D)] and 15 anisometropic amblyopes (SER:+5.34±1.68D) were recruited. All participants performed a dichoptic direct size comparison test using the method of adjustment while wearing their full spectacle corrections. Participants were asked to adjust the size of a dichoptically dissociated paired-square target. Two configurations: 1) a white square on black background (WoB), and 2) a black square on white background (BoW) were adopted. For all presentations, one square was always presented at full contrast with a fixed size through a stereo shutter goggle in the amblyopic eye (non-dominant eye) (for both BoW and WoB), while its counter-half was presented in the fellow eye under various interocular contrast levels with adjustable size. An average of five measurements was adopted as the threshold.
The matching size in the dominant /fellow eye increased monotonically with the decrease in interocular contrast ratio for both normal and amblyopes under both BoW and WoB conditions (ANOVA, P<0.05). Surprisingly, the matching size in the fellow eye of amblyopes differed drastically between the WoB and BoW condtions (P<0.05), while normal controls exhibited similar outcomes (P>0.05). This asymmetry could not be repeated in normal controls with one eye blurred with Bangerter filters.
Interocular difference in contrast is related to the measurement of aniseikonia in both normal and amblyopic participants. Moreover, the discrepancy of aniseikonia under different backgrounds observed in amblyopes revealed a unique visual deficit. Any attempt to eliminate aniseikonia in amblyopes should consider their asymmetric responses under black and white backgrounds.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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