ON-Pathway Visual Acuity Deficits in 8-12 Years Old Children with Unilateral Amblyopia

Abstract

"Purpose: Conventional recognition visual acuity (VA) tests, using black optotypes on white background, do not detect ON-pathway amblyopia deficits. This pilot study tests the hypothesis that VA testing with white optotypes on black background is more sensitive in detecting amblyopia than with black optotypes on white background. Methods: Two groups of children aged 8-12 were enrolled. The amblyopic group (N=13) had a best-corrected VA of 20/32 or worse in the amblyopic eye and an interocular VA difference of ≥0.2 logMAR. The control group (N=16) had best-corrected VA equal to or better than 20/25 and had an interocular VA difference of ≤0.1 logMAR. Participants’ VA were tested monocularly with an ETDRS program using the Amblyopia Treatment Study protocol and reported as a Score. Two optotype polarities were randomized, and tests were repeated after 30 minutes. VA in Scores were compared between amblyopic, fellow, and control eyes for both polarities. Results: For amblyopic eyes, the mean VA Score was significantly lower for white than for black optotypes (57.85±10.72 vs 61.46±10.10, p<0.001), indicating that amblyopic eyes had more difficulty seeing white than black optotypes. For fellow eyes, the mean Score was marginally significantly lower for white than for black optotypes (85.77±3.23 vs 87.73±4.61, p=0.03). No significant differences were found in control eyes (87.70±3.38 vs 88.02±4.03, p=0.63). Conclusions: VA in amblyopic eyes is 3.6 letters (~0.07 logMAR) worse when measured with white optotypes than black optotypes, indicating that white optotypes have higher sensitivity in detecting amblyopia ON-pathway deficit."