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Aixa Alarcon, Len Zheleznyak, Martin Banks, Geunyoung Yoon; Binocular combination of optically-induced asymmetric interocular blur. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2660.
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© ARVO (1962-2015); The Authors (2016-present)
It has been reported that interocular mirror symmetry in the aberrations (or optical blur) is present in the normal population. The goal of this study was to investigate the effects of interocular differences of monocular blur orientation on binocular blur perception.
Eight cyclopleged subjects were asked to binocularly view a stimulus under 3 aberration conditions and to match the subjective blur by inducing defocus to an unaberrated stimulus in 0.05D increments. A binocular adaptive optics vision simulator was used to correct subjects’ native aberrations, induce the 3 aberration conditions and to induce defocus for the blur matching task for a 6mm pupil. A monochromatic (550nm) binary noise image with random edge orientation served as the stimulus. The aberration conditions consisted of 0.5 and 1D astigmatism and 1μm coma. The aberration orientation of the right eye was rotated 0 and 90 degrees (i.e. equivalent and orthogonal, respectively) in the case of astigmatism and 0, 90 and 180 degrees in the case of coma while the left eye’s aberration was held fixed at 0 degrees for all conditions. In the coma condition, right eye orientations of 0 and 180 degrees correspond to a binocular mirror asymmetry and symmetry of blur orientation, respectively. Two subjects participated in the blur matching experiment in the 0.5D astigmatism condition, and 8 subjects participated in the remaining conditions.
Bilateral equivalent and orthogonal astigmatism of 0.5D resulted in significantly different blur matches of 0.53±0.05 and 0.36±0.09D, respectively (p<0.01, Student’s t-test). However, the blur matches for equivalent and orthogonal astigmatism of 1.0D did not differ significantly (0.81±0.24 and 0.79±0.21D, respectively). In the case of coma, as the right eye aberration rotated 0, 90 and 180 degrees with respect to the left eye with 0 degree, the blur match decreased (0.93±0.42, 0.80±0.29 and 0.83±0.37D, respectively). The perceived blur of coma with bilateral mirror symmetry (180-0 degree) was significantly less than the case of mirror asymmetry (0-0 degree) (p<0.01, Student’s t-test).
Binocular blur perception is reduced when interocular blur orientations differ. This finding suggests a compensatory mechanism of the binocular visual system to cope with different interocular blur orientation, however its capacity likely depends on the magnitude and relative orientation of blur between the eyes.
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