Flash Electroretinogram (ERG)
What does it do?
A Flash ERG (FERG) is a test which measures the electrical response of the eye’s light-sensitive cells (rods and cones). It also checks other cell layers in the retina.
Why did my doctor order this test?
A FERG will give your doctor information about the cells in your retina which give you color vision, detailed contrast detection, night vision and peripheral vision.
How is the test done?
Patients are seated comfortably in a recliner (if they choose), their pupils are dilated with eye drops, and they remain in a darkened room for about 45 minutes. After the 45 minutes, the patient’s eyes are numbed with an anesthetic eye drop and then a contact lens electrode is placed on the eye. Another wire is placed on the top of the head. The patient will look at a series of different colored flashes of light as the electrode picks up the retinal response. No response is required from the patient.
How should I prepare for the test?
If you wear contact lenses, be sure to bring your lens case and solution. You cannot wear contacts during the test. You should not wear any eye makeup to your test. Your hair should be clean and dry at the time of the test with no hairspray, gel or oil in your hair that may interfere with our ability to get a good recording from the scalp electrode. If you have difficulty driving when dilated, you will need to arrange for a driver. You may wish to bring your sunglasses to the appointment to wear after the test.