A clinically convenient test to measure binocular balance across spatial frequency in amblyopia

Abstract

Summary Amblyopia is a visual disorder that originates from the brain. It exhibits no pathology in the eye. Studies have shown that measuring both visual acuity and binocular balance for assessing amblyopia could be more helpful. However, tests that measure binocular balance are time-consuming, often exceeding 30 min. Their long test durations prevent them from being used in the clinic. For this reason, we have developed a quick (i.e., about 7 min) and precise tool that quantitatively measures binocular balance of patients with amblyopia. The new test can capture binocular imbalance that is typically exhibited at high spatial frequency in amblyopes. In addition, it has an excellent test-retest reliability and repeatability between two experimental sessions. We hope that our newly developed test can pave the road for physicians and researchers to better assess and diagnose amblyopia and other visual disorders that disrupt binocular balance beyond the laboratory.

The shift in sensory eye dominance from short-term monocular deprivation exhibits no dependence on test spatial frequency

“…It is thus not surprising to find a stable binocular balance across spatial frequency in normal observers. In fact, a flat sensory eye dominance vs. spatial frequency curve in normal adults has also been found in previous studies measured with binocular combination [ 11 , 23 , 26 ] and binocular rivalry [ 22 ]. However, sensory eye dominance of different types of subjects could differ on the character of spatial frequency dependence, such as amblyopia [ 23 ] and myopic anisometropia [ 35 ], which is worthy of further study in the future.…”

“…The binocular orientation combination task has been shown to have a good reliability to be able to extend binocular combination measurements to higher spatial frequencies than previously measured. This new approach allows us to assess the deprivation effect at higher spatial frequencies [ 25 , 26 ]. However, as we show in Fig.…”

“…As was the case in our previous study [ 26 ], there was an alignment phase and a test phase in a typical trial of the binocular orientation combination task. During the alignment phase, subjects were asked to align the dichoptic presented crosses with fusion surrounding frame and diagonal bars in the two eyes.…”

“…To address this issue, we conducted a binocular orientation combination task [ 25 ] with a previously validated method of adjustment [ 26 ] where subjects were asked to adjust the contrast in the dominant eye to obtain a balanced binocular percept to measure the changes of binocular balance at different spatial frequencies after short-term monocular deprivation. This task using the method of adjustment only takes about 3 min for each spatial frequency, and has good test–retest reliability similar to the task with the method of constant stimuli [ 26 ]. Here, we chose spatial frequencies of 0.5, 4, and 6 c/d.…”

Modulation of mean luminance improves binocular balance across spatial frequencies in amblyopia

“…For instance, amblyopic observers who have been fully treated with the standard patching therapy and have achieved normal monocular visual acuity can have a binocular imbalance that peaks at high spatial frequencies ( Chen et al., 2021 ; Ding et al., 2013 ; Kwon et al., 2015 ; Mao et al., 2020 ). Psychophysical studies have examined binocular imbalance of amblyopes across spatial frequencies (0.5-4 c/deg) using a phase combination task ( Ding et al., 2013 ; Ding and Levi, 2014 ; Ding and Sperling, 2006 ), a dichoptic letter chart ( Kwon et al., 2015 ) and a binocular orientation task ( Mao et al., 2020 ; Min et al., 2022 ). Moreover, studies report no correlation between the improvement of visual acuity and the depth of interocular suppression during monocular patching treatment ( Chen et al., 2019 ; Kehrein et al., 2016 ).…”