Imbalanced Sensory Eye Dominance of Surgically Aligned Late-onset Acute Acquired Concomitant Esotropes with normal stereopsis

Abstract Background: Adults with late-onset acute acquired concomitant esotropia (AACE) have chance to develop normal binocular functions including a balanced ocular dominance before the onset of esotropia. For most patients, strabismus surgery re-establishing the ocular alignment indeed effectively restore stereopsis and visual acuity to the normal level. However, it is unclear whether they have already acquired balanced two eyes.Methods: 11 surgically aligned patients with AACE (24.3 ± 1.5 years; mean ± SE) and 14 adults with normal vision (26.1±1.2 years) participated in our experiments. All patients had normal binocularity and stereopsis. Using binocular phase combination paradigm, sensory eye dominance was quantified as the interocular contrast ratio, termed balance point, at which the contribution of each eye to the perception of cyclopean grating were equal.Results: Normal controls had a mean balance point value close to unity (0.95±0.01), while AACE group exhibited evident binocular imbalance (0.76±0.05), which was significantly different from control group (t (10.45) = -3.485, p = 0.006) . The balance point value didn’t depend on the interval from AACE onset to strabismus surgery (r = -0.357, p = 0.281) or the interval from the surgery to examination of sensory eye dominance (r = -0.105, p = 0.759).Conclusions: Although strabismus surgery effectively straightened AACE patients’ ocular alignment and even conferred them normal stereopsis, late-onset AACE patients’ two eyes were still not balanced. These results indicated that binocular imbalance might be a risk factor for adult AACE.