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An electroretinography (ERG) test, also known as an electroretinogram, measures the electrical response of the light-sensitive cells in your eyes.
These cells are known as rods and cones. They form part of the back of the eye known as the retina. There are around 120 million rods in the human eye and 6 to 7 million cones. The cones are responsible for the eye’s color sensitivity. They reside mostly in your eye’s macula. The rods are more sensitive to light than the cones, but they’re not more sensitive to color.
Your doctor may perform an ERG to determine if you have an inherited or acquired disorder of the retina, such as:
An ERG may also help your doctor assess your need for retinal surgery or other types of eye surgery, such as the removal of cataracts.
The following occurs during an ERG:
If your results are normal, they’ll show the wave patterns of a normal eye in response to each flash of light.
Abnormal results may indicate any of the following conditions:
There are no risks linked to the ERG. You may feel a slight discomfort during the procedure. The placement of the electrode feels something like having an eyelash lodged in your eye. Your eyes may feel slightly sore for a short time after the test.
In very rare cases, some people suffer from a corneal abrasion from the test. If this happens, your doctor can detect it early and treat it easily.
Monitor your condition after the procedure and follow all aftercare instructions your doctor gives you. If you have continued discomfort following an ERG, you should contact the doctor who performed the test.
Your eyes will likely feel sensitive after the test. You should avoid rubbing your eyes for up to an hour after the test. This may cause corneal damage because they’ll still be numb from the anesthetic.
Your doctor will discuss your results with you. They may order further tests to assess your eye. You may need surgery if you have a disorder such as retinal separation or trauma.
Your doctor may prescribe you medication to treat other retinal conditions.
Written by: Corinna Underwood
Medically reviewed on: Jan 26, 2016: Mark R. Laflamme, MD
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