Abstract
Purpose :
Standard-of care assessment for children with amblyopia includes measuring best-corrected monocular visual acuity (BCVA), with the non-viewing eye occluded. Yet, when visual input from the fellow eye is occluded, the central suppression scotoma that is fundamental to amblyopia may have reduced impact on amblyopic eye (AE) BCVA. As a result, AE BCVA measured with occlusion may not accurately represent AE function during natural binocular viewing. We compared AE BCVA with monocular versus binocular (dichoptic) viewing, and determined whether any differences under the two viewing conditions were associated with performance on tests of fixation instability, reading, and motor skills with natural binocular viewing.
Methods :
AE BCVA of 50 children (6-12y) with amblyopia (monocular E-ETDRS AE BCVA: 0.2-0.5 logMAR) was tested under monocular and dichoptic viewing conditions with an Optec Vision Tester. In the monocular condition, 8 Sloan letters were presented to the amblyopic eye on each line. In the dichoptic condition, 4 letters were presented to the fellow eye, 4 letters to both eyes, and 4 letters to the amblyopic eye (8 letters to each eye). In both conditions, AE BCVA was defined as the smallest optotype size at which the child identified >75% of letters presented to the amblyopic eye. Fixation stability was calculated as the 68% bivariate contour ellipse for 20 sec binocular fixation, reading speed was determined with silent binocular reading of age appropriate passages using a Readalyzer, and motor skills were assessed with the Movement Assessment Battery for Children-2.
Results :
72% of children with amblyopia had better AE BCVA when tested in the monocular than dichoptic condition (mean difference+SE=0.12+0.02 logMAR), with 38% of children performing 2-4 lines better in the monocular condition. The difference between conditions was correlated with fixation instability of the amblyopic and fellow eyes (r=0.56 and 0.72, p<0.001), reading speed (r=-0.77, p<.0001), manual dexterity (r=-0.35, p=0.01), and aiming/catching skill (r=-0.41, p=0.01).
Conclusions :
AE BCVA measured with occlusion may not accurately represent its function during natural binocular viewing. The difference between dichoptic and monocular AE BCVA is potentially a useful index of suppression, with moderate to strong associations with fixation stability, reading speed, and motor skills.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.