Reliability of Fixation Preference for Detecting Amblyopia in Strabismic Patients

PURPOSE: To evaluate the association between fixation preference (FP) and amblyopia in strabismic patients. METHODS: This study includes 50 patients with horizontal, vertical or mixed strabismus of at least 10 prism diopters. Best-corrected monocular visual acuity (VA) was measured using Snellen E-chart and the presence of amblyopia was determined accordingly; FP was evaluated and graded from 0 to 3. RESULTS: Of 50 patients, including 27 female and 23 male subjects, 29 (58%) patients had FP but 18 (36%) subjects were truly amblyopic. Overall, the sensitivity and specificity of FP for detection of amblyopia was 88.9% and 59.4% respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 55.2% and 90.5% respectively. Sensitivity, PPV and NPV were significantly higher in esotropic as compared to exotropic patients. Strong monocular FP was correlated with more than 3 lines of interocular difference (IOD) in visual acuity (P=0.001). CONCLUSION: Although FP is not an ideal method for diagnosis of strabismic amblyopia, it has high sensitivity, PPV and NPV in esotropic patients and in subjects with more than 3 lines of IOD in VA.