Measuring suppression size and its implications for amblyopia management

CLINICAL RELEVANCE: Amblyopia is a neurodevelopmental binocular disorder, managed mostly by patching and increasingly by dichoptic binocular therapy. The criteria to cease therapy is usually determined by monocular (amblyopic eye) visual acuity improvement. Grades of binocular vision may also provide additional clinical information for amblyopia management. BACKGROUND: Absence of simultaneous macular perception (SMP, Grade 1 of binocular vision) is indicative of suppression. In amblyopia, all grades of binocular vision are reduced or absent. With therapy, improvements in these grades of binocular vision may occur sequentially or simultaneously. The present study investigated these patterns. METHODS: A retrospective study was conducted. Patients who had undergone anti-suppression vision therapy for amblyopia were included. Visual acuity, stereoacuity, and suppression size were measured before and after therapy. Suppression size was measured using a commercially available device (VTS4) that presents dissimilar dichoptic targets. RESULTS: < 0.001) was also observed. A greater proportion of patients (71%) showed a reduction in suppression size compared with those showing improvement in stereoacuity (21%), particularly among patients with larger baseline suppression size. In those starting with suppression size < 1°, the potential for improving the stereoacuity was higher (100%). CONCLUSION: Greater improvement in Grade 1 binocular vision compared with Grade 3 (stereoacuity) suggests a hierarchical recovery of binocular function in amblyopia. Additional therapy sessions may be considered to improve stereoacuity once suppression size is reduced to ≤1°. Measurement of SMP, alongside visual acuity and stereoacuity, may provide additional insights for amblyopia management.