Pathological suppression of binocular vision in stroke.

PURPOSE: Two prior studies suggested a relationship between spatial neglect and reduced diplopia reporting. In spatial neglect with visual extinction phenomenon, the double image on the neglected side may be extinguished from perception, representing a pathological binocular suppression. We retrospectively reviewed the binocular vision testing battery routinely performed at one inpatient rehabilitation hospital vision clinic to better understand reduced diplopia reporting and look for evidence of pathological suppression. METHODS: One hundred fifty-five consecutive patient charts were retrospectively reviewed. Significant predictors of denial of double vision in patients with recent stroke and strabismus (N = 55) or prism induced strabismus (N = 98) were identified with logistic regression. Additionally, three clinicians rated the likelihood (1 to 10) of suppression in each case and predictors of the rating were identified with a cumulative logit model. Cases with likelihood rating >7/10 were flagged and examined individually. RESULTS: Only 15 of 155 patients passed all suppression tests administered (9.7%). Fifty-three percent of patients with strabismus actively denied diplopia. When controlling for significant effects of age, patients with spatial neglect had 3.9 greater odds of denying diplopia (OR (95% CI) 3.91 (1.70, 8.96)). Inter-ocular acuity difference and hemianopia were not significant predictors. A high likelihood of suppression was associated with parietal lobe injury, (3.40 (1.22-9.30)). The side of the brain was not significant (α = 0.05). Five patients had a likelihood rating greater than 7 out of 10 and so were likely exhibiting pathological suppression. CONCLUSIONS: Denial of diplopia is associated with spatial neglect and age. In some cases, this likely represents a pathological suppression of binocular vision.