The retina is the part of the eye that detects light and images, much like the film in a camera. After detecting an image, the retina transmits electrical signals to the brain, where the final picture is registered. Electroretinography assesses the electrical activity of the retina, thus giving an accurate assessment of retinal function.
Electroretinography takes approximately 30 minutes to perform. The pet is dark-adapted prior to the procedure; this involves sitting in a dark room for 15 minutes to allow the retina to become maximally sensitive to light. Once the pet is dark-adapted we place a contact lens on the cornea and shine lights in the eye. Small electrical probes on the skin detect electrical activity, giving an assessment of retinal function. The procedure is not painful, and most animals do not require a sedative for electroretinography.
The purpose of electroretinography is to determine whether the retina is functioning properly. There are several conditions in which the retina does not function normally, resulting in vision loss. One of these is progressive retinal atrophy, a genetic condition that causes slow, gradual but non-painful vision loss. Older dogs can develop sudden acquired retinal degeneration, in which they can lose vision overnight. Electroretinography can detect these conditions and therefore determine if a pet is blind from disease of the retina.
If a pet has cataracts and the owner is interested in cataract surgery, we will generally recommend an electroretinogram to make sure that the retina is functioning normally. A cataract, which is an opacity in the lens, can prevent the ophthalmologist from visualizing the retina during the ophthalmic examination. The electroretinogram can provide valuable information about the health of the retina, and whether or not the pet will be able to see following cataract surgery.