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Electroretinography

Electroretinography is a non-invasive means to test the function of the retina. The retina is the light sensitive layer at the back of the eye which absorbs photons of light and converts them into electrical impulses which are transmitted along the optic nerve to the brain to enable vision to occur.

The electroretinogram (ERG) is to the retina what the electrocardiogram (EKG) is to the heart. Both record electrical activity and result in a waveform which can be examined and measured.

The ERG is usually recorded through three electrodes attached to the patient. One is a gold electrode embedded in a small contact lens which is applied to the cornea after using a local anesthetic drop to prevent discomfort. To prevent discomfort. The other 2 electrodes are very fine needles inserted into the skin on the head and neck.

The ERG is stimulated by flashing lights of varying color, intensity and frequency at the eye. The animal is often placed in a darkened room for 20 minutes prior to the test to allow the retina to become more sensitive in the dark. The test itself takes about 15 minutes and the results are immediately available

We use the ERG in animals with cataracts to make sure the retina in functioning normally prior to cataract surgery. Other indications for ERG testing are animals with sudden blindness and to help diagnose inherited retinal degenerations and drug induced retinal damage.