The effect of optical treatment on refractive amblyopia: comparison of treatment responders and non-responders

Abstract

Purpose : We previously found that four months of optical treatment in children with newly diagnosed refractive amblyopia were associated with improvement in visual acuity (VA), psychophysical grating acuity (GA) and pattern-onset visual evoked potentials (POVEP), albeit still significantly poorer compared to non-amblyopic children. The purpose of the present study was to characterize the POVEPs (morphology, component amplitudes/latencies and meridional anisotropies) of the amblyopic children divided into subgroups of responders and non-responders to optical treatment.

Methods : Newly diagnosed refractive (non-strabismic) amblyopes were recruited. Baseline POVEPs and GAs in response to 4 cycle per degree achromatic sinewave gratings were assessed when spectacles were dispensed (Visit 1) and after 4 months of optical treatment (Visit 2). Gratings were oriented at the principal astigmatic meridians (Meridians 1 & 2) monocularly and 45, 90, 135 and 180 degrees binocularly. Amblyopes who improved VA by >10 letters (i.e. <0.20 logMAR) were classified “responders” and the rest “non-responders”. The effects of orientation (Meridians 1 & 2), visit (Visit 1 & 2) and treatment outcome (Responder / Non-responder). Binocular data was analysed using repeated measures ANCOVA.

Results : Eleven responders and 11 non-responders (aged 3.8 - 7.1 years) completed 4.9 ±1.2 months of treatment. VA improved by 12 and 0.5 letters respectively. There was significant improvement in monocular C3 amplitude (5.73 ±2.47 μV, p = 0.048) and GA (0.51 octaves, equivalent to approximately 2 lines in logMAR VA, p < 0.0001) in responders but not non-responders. Monocular C3 latency was 8.7 ±3.6 ms faster in responders at both visits as compared to non-responders (p = 0.028), but there was no significant difference between visits for both groups. Binocular results had no significant inter-group differences in all outcome measures. There were no significant inter-group differences in meridional anisotropies for both monocular and binocular results.

Conclusions : Treatment responders had significantly better monocular POVEP and GA compared to non-responders. Amblyopes with shorter monocular C3 latencies at the point of diagnosis were more likely to respond to optical treatment. Further studies may explore baseline C3 latency as a predictor of treatment response.

This is a 2020 ARVO Annual Meeting abstract.