Evaluation of retinal function and morphology in isoametropic amblyopia

Purpose: To observe the photoreceptor anomalies in cases of ametropic amblyopia. Methods: A prospective study with 25 isoametropic amblyopic children in the age group of 5-14 years and 25 age-matched controls was done. Examination included refraction, best-corrected visual acuity (BCVA), and color vision. Adaptive optics (AO) and multifocal electroretinogram (mf-ERG) were done to assess the anatomy and function of photoreceptors. The subgroup analysis of the improved and non-improved groups was done. Results: The mean cone density in cases and control in the superior, temporal, and nasal quadrants was respectively as follows (21640 +/- 5713, 24040 +/- 3386, P = 0.01) (19755 +/- 6282, 21832 +/- 2911, P = 0.03) (19897 +/- 5418, 22171 +/- 3660, P = 0.01) (20768 +/- 4799, 22819 +/- 3241, P = 0.01). The amplitude of N1 wave and P1 wave in cases was significantly low compared to the controls. Cases with subnormal color vision had reduced BCVA (0.55 +/- 0.018) in comparison to the children with normal response (0.350 +/- 0.014). Cone density was also significantly reduced in children with subnormal color vision. Sixteen out of 25 cases showed BCVA improvement with spectacles. Baseline cone density was found to be significantly higher in the improved group. There was no correlation between BCVA and AO parameters. Conclusion: Patients with ametropic amblyopia show subnormal photoreceptor properties than controls. Low cone density may be associated with defective color vision and poor prognosis in these cases.