Evaluation of Fusion and Stereopsis in Anisometropic Patients

Abstract Background Binocular vision has many important advantages on monocular vision as it helps in determination of the distance of an object, gives much greater depth of perception, and the ability to have stereopsis and view the world in three dimension (3D). There is an evidence that binocular vision is present in many patients with anisometropia even who have amblyopia but with grades lower than normal. Purpose This study evaluates the effect of anisometropia on BSV functions. Method sixty-four patients above 6 years with anisometropia equal to or more than 2.5D never had their vision corrected either by glasses or refractive surgeries or went on patching treatment, Anisometropic patients were devided into two groups amblyopic group (AA) and non-amblyopic group (NA) were examined for assessing their fusion by Worth four dot test and their stereopsis by fly test (Titmus stereo acuity test) by their best corrective glasses based on their cycloplegic refraction. Results Anisomyopes shows better stereopsis 62% of them and better fusion 65% of them than anisohypropes which had only 8% with good stereopsis and 32% with good fusion. However, antimetropes showed bad fusion and stereopsis as all of the five cases have amblyopia. Only 29.5% of anisomyopes have amblyopia but 68% of anisohypropes have amblyopia. As regard worth four dot test (P < 0.001), as 90.6% of cases with amblyopia had suppressed eye but only 9.4 % of this amblyopic cases had normal fusion. However, in patients without amblyopia 15.6% had suppressed eyes but 84.4% had normal fusion. As regard Titmus test there was statistically significant difference between both groups (P < 0.001), as 100 % of cases with amblyopia had bad stereo acuity but 28.1% of patients without amblyopia had defect in their stereo acuity. Conclusion Fusion and stereopsis as binocular single vision functions were significantly affected in AA patients with best-corrected anisometropic glasses than in NA patients.