Effect of Primary Occlusion Therapy in Asymmetric, Bilateral Amblyopia

Many bilateral amblyopia patients have asymmetric visual acuity (VA). There is no standard treatment for these patients, and outcomes have not been well described. Our goal is to compare VA outcomes in this group based on timing of occlusion therapy.

Retrospective interventional comparative case series.

Setting: Institutional practice. PatientPopulation: Patients diagnosed with amblyopia at Boston Children's Hospital between 2010 and 2014. InclusionCriteria: VA ≥ 0.3 logMAR bilaterally by objective optotype-based measures, interocular difference (IOD) ≥ 0.18 logMAR, age 2-12 years. ExclusionCriteria: Loss to follow-up, managed surgically, deprivation amblyopia. Patients had either primary or secondary occlusion (primary = initiated when VA ≥ 0.3 logMAR bilaterally; secondary = initiated to correct residual IOD once VA improved to ≤0.18 logMAR in the stronger eye). ObservationProcedure: Patient demographics, VA, IOD, and stereopsis were compared between groups. OutcomeMeasures: VA improvement at 12-18 months and at last visits.

Of 2,200 patients reviewed, 167 (7.6%) had asymmetric, bilateral amblyopia; 98 met inclusion and exclusion criteria. Patients were equally divided between primary (n = 50) and secondary (n = 48) occlusion groups. There were no differences in demographics, baseline VA, or IOD between groups (P ≥ .22), although the primary occlusion group had a higher proportion of strabismic amblyopia (P = .007). VA in both eyes, IOD, and stereopsis improved similarly between groups, even after stratifying by amblyopia subtype (P ≥ .48). The secondary occlusion group was more likely to achieve 20/30 bilaterally and IOD ≤ 1 line at 12-18 months (P ≤ .4), although this equalized by the last visit.

In patients with asymmetric, bilateral amblyopia, VA improved by 4 lines in the weaker eye and 2 lines in the stronger eye, while IOD improved by 2 lines, irrespective of occlusion status. Primary occlusion thus provided no further benefit over spectacle correction alone.