Quantitative evaluation of the electroretinogram.

The assessment of an electroretinogram (ERG) as normal, abnormal or absent is too imprecise an estimation to inform ophthalmic surgeons about the prospective visual functions. For example, an abnormal or subnormal ERG includes an almost normal as well as an almost absent ERG. Furthermore, whether an ERG is labelled as absent depends on the amplitude of the electrical background activity. A much better information can be provided by expressing the ERG in percentages of the normal value.