n. a method of recording changes in the electrical potential of the retina when it is stimulated by light; the recording itself is called an electroretinogram (ERG). One electrode is placed on the eye in a contact lens and the other is usually attached to the back of the head. In retinal disease the pattern of electrical change is altered. The technique is useful in diagnosing retinal diseases when opacities, such as cataract, make it difficult to view the retina or when the disease produces little visible change in the retina.
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