Pattern ERG in amblyopia.

The authors have recorded pattern ERGs in 62 amblyopic children. In 12 who were occluded up until the morning of the test, the occluded eye response was reduced, and the ratio ([response amplitude of amblyopic eye]/[response amplitude of fellow eye]) was greater than unity. In the remainder, the ratio was considerably less than unity. Ratios of less than 1.0 were found for anisometropic, esotropic, exotropic, and microtropic amblyopes. The ratio was not related to visual acuity or to squint but was higher in those children whose vision was improved by orthoptic treatment. In a group of older children recalled to the clinic, the ratio was 1.0 in those who had maintained equal visual acuity and was less than unity in those children whose acuity had regressed after treatment, or had not improved during treatment. The reduction of the pattern ERG in amblyopes occurs without a corresponding reduction in the focal ERG. In adult amblyopes, the relationship between loss of acuity, loss of grating contrast sensitivity, and the reduction in the PERG is complex and may differ according to the type of amblyopia.