Abstract: PURPOSE: It appears that short-term monocular deprivation enhances the binocular contribution of the deprived eye in human adults, i.e., adult ocular dominance plasticity. And the ocular dominance plasticity induced by short-term deprivation is not dependent on test spatial frequency. Current research is limited to luminance-modulated (first-order) stimuli. However, little is known regarding whether there is ocular dominance plasticity in human adults for stimuli defined by modulations in contrast (second-order stimuli). To address this issue, we conducted a study to investigate ocular dominance plasticity in second-order binocular combination and its relationship with spatial frequency.
METHODS: Sixteen healthy young adults (mean age ± SD: 24.56 ± 1.03 years) with normal vision participated in the study. The experiment consisted of three consecutive stages: a measurement of BP (balance point) before patching, a patching stage (patch the dominant eye 2 hours determined by the hole-in-the-card test) and measurement of BP after patching (six sessions at 0, 3, 6, 12, 24, 48 minutes after the removal of the patch). We use a translucent patch for short-term monocular deprivation. In this study, we utilized a binocular orientation combination task with stimuli of first and second order at 0.5, 2, and 4 cycles/degree (c/d). Each measurement included seven contrast ratios. By fitting a logistic function, we fitted a psychometric function and then estimated the main outcome called BP. BP was defined as the dBContrastRatio (i.e., 20 * log10 contrast ratio) with perceived orientation of 0°. Changes in BP values were utilized to quantify the impact of patching on ocular dominance.
RESULTS: Short-term monocular deprivation can cause a shift in the ocular dominance for second-order stimuli. AUC (the area under the curve) means the summation of ΔBP from 0 to 48 minutes after monocular deprivation. The more negative the AUC, the stronger the patching effect for the patched eye. There was no significant difference in AUC for spatial frequencies of 0.5, 2, and 4 in the second-order.
CONCLUSIONS:These results indicate that there exists ocular dominance plasticity for second-order stimuli and are associated with spatial frequency-independent.

Key words: Ocular dominance plasticity, Second-order, Spatial frequency, Binocular combination.