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Zidong Chen, Jinrong LI, Benjamin Thompson, Robert Hess, Daming Deng, Minbin Yu; The effect of Bangerter filters on binocular summation in anisometropic amblyopia. Invest. Ophthalmol. Vis. Sci. 2014;55(13):798.
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Binocular summation has been demonstrated in patients with amblyopia when suppression of the amblyopic eye is minimized. The aim of this study was to investigate whether penalization of the fellow eye with Bangerter filters would facilitate binocular contrast summation in patients with anisometropic amblyopia.
Contrast sensitivity (CS) was assessed psychophysically using Gabor patches combined with a two alternative forced choice orientation discrimination task and a 3 down 1 up staircase procedure. 22 controls and 26 patients with anisometropic amblyopic participated in the study. CS was measured for five spatial frequencies (0.5, 1, 3, 9 and 16 cycles per degree; cpd) under binocular and monocular viewing conditions with no penalization and for 3cpd and 9cpd with 0.2 and 0.4 strength Bangerter filters placed over the fellow (or dominant) eye. Testing order was randomized. Binocular summation ratios (BSRs) were calculated for each spatial frequency by dividing binocular sensitivity by the monocular sensitivity of the most sensitive eye.
In the absence of Bangerter filters, control observers showed binocular summation at all spatial frequencies whereas amblyopes showed binocular summation at 0.5 and 1 cpd only. For the majority of amblyopes, contrast sensitivity for medium spatial frequencies (3 and 9 cpd) could be equated between the two eyes by placing a 0.4 strength Bangerter filter over the fellow eye. This resulted in measurable binocular summation for the 3 cpd stimulus. The 0.2 strength filter tended to result in poorer contrast sensitivity for fellow eyes than amblyopic eyes.
Under certain conditions Bangerter filters may promote binocular contrast summation in patients with anisometropicamblyopia.
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