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Related to electroretinograph: electroretinography
ERG; an instrument for measuring the electrical response of the retina to light stimulation. The basic component of the ERG is a contact lens containing an electrode, which is placed on the surface of the eye. Electrical activity of the retina is magnified and recorded as waves similar to those seen on an electrocardiograph. Signals from a diseased retina are reduced in size and slower than normal. ERG is especially useful in confirming a diagnosis of retinitis pigmentosa before visible signs can be detected with an ophthalmoscope.