Dichoptic Spatial Contrast Sensitivity Reflects Binocular Balance in Normal and Stereoanomalous Subjects

Abstract

To study binocular balance by comparing dichoptic and standard monocular contrast sensitivity function (CSF) in stereonormal and stereoanomalous/stereoblind amblyopic subjects. METHODS. Sixteen amblyopes and 17 controls participated. Using the capability of the passive three-dimensional display, we measured their CSF both monocularly and dichoptically at spatial frequencies 0.5, 1, 2, 4, and 8 cpds using achromatic Gabor patches on a luminance noise background. During monocular stimulation, the untested eye was covered, while for the dichoptic stimulation the untested eye viewed background noise. Dichoptic CSF of both eyes was acquired within one block. RESULTS. In patients with central fixation, dichoptic viewing had a large negative impact on the CSF of the amblyopic eye, although it hardly affected that of the dominant eye. In contrast, dichoptic viewing had a small but significant effect on both eyes for controls. In addition, all participants lay along a continuum in terms of how much their two eyes were affected by dichoptic stimulation: by using two predefined contrast sensitivity ratios, namely, amblyopic sensitivity decrement and dichoptic sensitivity decrement, not only did we find a significant correlation between these variables among all participants, but also the two groups were identified with minimum error using a cluster analysis. CONCLUSIONS. Dichoptic CSF may be considered to measure visual performance in patients with altered binocular vision, because it better reflects the visual capacity of the amblyopic eye than the standard monocular examinations. It may also be a more reliable parameter to assess the efficacy of modern approaches to treat amblyopia.

Fixation instability, astigmatism, and lack of stereopsis as factors impeding recovery of binocular balance in amblyopia following binocular therapy

“…Visual acuity is still the standard clinical parameter for characterizing amblyopic status and for the management of several diseases affecting the visual system, even though it has been extensively reported that luminance contrast sensitivity (CS) is highly related to the quality of vision 86 . Moreover, CS provides a more complete picture of spatial vision compared to visual acuity, besides its potential to measure binocular balance in amblyopic patients 3 , 64 , 87 . In line with our results, significant contrast sensitivity improvements have been reported in adult amblyopic eyes following dichoptic training 44 and perceptual learning 45 , 46 .…”

“…Contrast sensitivity was the inverse of the contrast at the last correctly identified patch. For characterizing changes in contrast sensitivity, a broad contrast sensitivity metric, the area under the log contrast sensitivity function (AULCSF) was used 63 , 64 . This was calculated by fitting a third-order polynomial to the log contrast sensitivity versus log spatial frequency data of each subject and integrating between the lowest and highest spatial frequencies 65 .…”

The effect of spatial structure on binocular contrast perception

“…In the research literature, several methods have been proposed to measure sensory eye dominance ( Ooi & He, 2020 ). One method involves assessing eye balance by adjusting the interocular contrast difference between the two eyes to null the effects of an interocular phase difference ( Ding & Sperling, 2006 ), orientation difference ( Yehezkel, Ding, Sterkin, Polat, & Levi, 2016 ), or masking ( Barboni et al, 2020 ). In amblyopic vision, the binocular imbalance depends on both spatial frequency and stimulus contrast, with more imbalance at higher frequencies and higher contrast ( Ding et al, 2013a ; Ding & Levi, 2014 ).…”

Fixation stability after surgical treatment of strabismus and biofeedback fixation training in amblyopic eyes

“…Here we reported that strabismic amblyopic eyes may benefit from BFT after surgical alignment of strabismus. Further studies with a large population may investigate the relations between clinical parameters, such as binocular balance [ 56 ], and visual improvements provided by BFT. In addition, to establish the proper criteria for selecting those patients who would more likely benefit from BFT for enhancing visual performance in amblyopic eyes.…”