Organic visual loss measured by kinetic perimetry and retinal electrophysiology in children with functional amblyopia

To demonstrate an organic (retinal) amblyogenic defect in functional amblyopes not responding to treatment.

Twenty-four children (Mean age: 5.9 ± 1.8 years; range: 4-10 years) with functional amblyopia were recruited for this study. All these children underwent complete ophthalmic and orthoptic evaluation. In addition, Kinetic Goldman Visual Fields (KGVF), Spectral Domain Optical Coherence Tomography (SD-OCT), full field flash electroretinograms (ffERG) and multifocal electroretinograms (mfERG) were also performed. Ratios were subsequently derived by comparing the amplitudes obtained from the amblyopic eye (AE) to the good eye (GE) for the a- and b-waves of the ffERG, as well as for the ring analysis of the mfERG.

KGVF showed a central scotoma of varying size (3°-7°) and density (absolute to relative), with increasing target size in 14/24 patients whose best post-treatment vision in the AE ranged from 20/100 to 20/40. The scotoma decreased in size and density with improving vision until a plateau of recovery was reached. The remaining 10/24 patients with a vision ≥ 20/30 showed no scotoma. SD-OCT showed no significant difference between the AE and GE. ffERG and mfERG were obtained in 18/24 patients. The ffERG AE/GE ratio was abnormal in 7 patients, 5 of which had large scotomas on KGVF. The mfERG ring 1 AE/GE ratio was significantly (p < .05) attenuated in 9/18 patients out of which 3 were no longer amblyopic. However, there was no significant difference (p > .05) in ring 1 AE/GE amplitude ratio between those who achieved 20/50-20/40 (.81 ± .26) and those with ≥ 20/25(.86 ± .25).

The combined findings of central scotoma on KGVF and mfERG anomalies in patients who did not achieve optimal vision with treatment suggest an underlying organic defect impairing macular function.