Dichoptic and Monocular Visual Acuity in Amblyopia

Purpose: Standard-of-care assessment for children with amblyopia includes measuring amblyopic eye best-corrected visual acuity (AE BCVA) with the fellow eye occluded. By definition, this abolishes the interocular suppression fundamental to amblyopia. Thus, measured AE BCVA may not accurately represent that eye's contribution to natural binocular viewing. We compared dichoptic and monocular AE BCVA and examined whether any differences were associated with eye-hand coordination or reading speed.

Design: Cross-sectional study.

Methods: Dichoptic and monocular AE BCVA of children aged 6-12 years (42 with amblyopia, 24 with recovered normal AE BCVA, 30 control) were measured. Stereoacuity, suppression, eye-hand coordination, and reading speed were also assessed.

Results: Overall, 81% of amblyopic children had worse dichoptic than monocular AE BCVA (mean difference=0.15±0.11 logMAR; P < .0001), and 71% of children with recovered normal AE BCVA had worse dichoptic than monocular AE BCVA (mean difference = 0.20±0.17 logMAR, P < .0001). Controls had no significant difference. The difference between dichoptic and monocular AE BCVA was correlated with performance in standardized aiming/catching (r = -0.48, 95% CI -0.72, -0.14) and manual dexterity tasks (r = -0.37, 95% CI -0.62, -0.06), and with reading speed (r = -0.38, 95% CI -0.65, -0.03).

Conclusions: Dichoptic AE BCVA deficits were worse than monocular AE BCVA deficits and were associated with reduced stereoacuity and suppression, consistent with the hypothesis that binocular dysfunction plays a role. Further, impaired eye-hand coordination and slow reading were associated with dichoptic, but not monocular, AE BCVA. Some children with amblyopia may benefit from extra time for school tasks requiring eye-hand coordination or reading.