Electroretinography in Dogs and Cats. Part II. Technique, Interpretation, and Indications

Electroretinography, a technique that objectively assesses the function of the retina, is used to evaluate the progression of retinal disorders. Part I of this two-part presentation discussed the morphologic and physiologic characteristics of the retina. The information presented in Part II can help practitioners determine when an electroretinogram (ERG) is recommended. In addition to the standard flash ERG, visual evoked potentials (VEPs) are useful for evaluating disorders that lead to blindness. The most common indications for electroretinography are presurgical evaluation of patients with cataracts, characterization of disorders that cause blindness, and identification of the extent of retinal damage caused by glaucoma. A flash ERG can only show changes that occur to the retina in advanced stages of glaucoma; whereas a pattern ERG (PERG) can record early, selective damage to ganglion cells in the retina.