Usher syndrome: correlation between visual field size and maximal ERG response b-wave amplitude.

Abstract

The evaluation of a patient affected with hereditary retinal degenerations is based on the combination of psychophysical (e.g., visual acuity, visual field) and objective measurements [(e.g., the electroretinogram (ERG)]. The ERG provides essential information on the amount and quality of functioning retina left. The a-wave of the full-field flash maximal ERG response reflects the combined activity of rod and cone photoreceptors, whereas the b-wave reflects the activity of both the rod-and the cone-driven postreceptoral pathways. Vision begins at the level of photoreceptors but is subsequently fine-tuned via a series of gain and filtering steps taking place both inside the retina and, of course, at the brain level. Therefore, among the ERG parameters, the b-wave of the full-field flash maximal ERG response offers, however imperfect it may be, the best approximation of the full visual potential of any given retina, as it already encompasses the gain of the visual response performed intraretinally by the bipolar cells. In addition, since both the rod-and cone-driven pathways can contribute to the detection of the test targets used conventionally to delimit visual fields with the Goldmann kinetic technique, the maximal ERG response b-wave is well suited also for correlation analysis between ERG and visual fields obtained under these conditions.KeywordsVisual FieldRetinitis PigmentosaRetinal DegenerationUsher SyndromeUsher Syndrome TypeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.