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An EOG, which stands for electrooculogram, is a test that measures the electrical signals in your eye. It helps doctors check the health of a cell layer at the back of the eye called the retinal pigment epithelium (RPE). The test records the difference in electrical charge between the front and back of your eye as you move it.
read more about EOG test ...An EOG test is not a routine eye exam. A specialist will order it to help diagnose specific, often inherited, diseases of the retina. It is particularly useful for confirming a diagnosis of Best's disease, a genetic condition that can cause vision loss. The test shows a doctor how well the important RPE layer of the retina is working.
The test is simple and painless. First, small sensors called electrodes are placed on the skin next to your eyes. You will then sit in a dark room for about 15 minutes to let your eyes adjust. A small light will appear, and you will be asked to follow it back and forth with your eyes. This is repeated with the lights on. The electrodes record your eye's electrical activity during these movements.
An EOG is often performed along with an ERG (electroretinogram), but they measure different things. The EOG measures the health of the RPE cell layer by tracking the electrical potential during eye movement.
The ERG, on the other hand, measures how the light-sensing cells (rods and cones) respond directly to flashes of light. Together, they give a more complete picture of retinal health.
The primary result doctors look for in an EOG is the "Arden Ratio." The test measures the resting electrical potential of the eye in the dark versus the light. In a healthy eye, the electrical charge increases significantly when the lights are turned on (the light peak). The doctor divides the light peak by the dark trough to get a number. An Arden Ratio of 1.8 or higher is normal; anything below 1.65 suggests a malfunction in the Retinal Pigment Epithelium.
The EOG is the "gold standard" test for diagnosing Best's Vitelliform Macular Dystrophy. In the early stages of this genetic condition, the retina may look fairly normal during a standard exam, or the vision may be unaffected. However, the EOG will almost always be abnormal. This allows doctors to identify the disease years before significant vision loss occurs, helping families understand the genetic risk.
No, the test is not painful. You may feel a slight sensation from the electrodes sticking to your skin, but the test itself does not cause any discomfort. You just have to sit still and follow a light.
The entire process usually takes about 45 to 60 minutes. This includes the time needed to set up the electrodes and for your eyes to adapt to both dark and light conditions.
Your doctor will provide instructions. Generally, you should not wear any makeup or lotion on your face. Your eyes might be dilated for the test, so you will likely need someone to drive you home afterward.
You would typically talk to your doctor about an EOG test if they recommend it. A retinal specialist may order this test if you have symptoms or a family history that suggests a rare genetic retinal disease. If you are experiencing unexplained changes to your central vision, discuss it with your eye doctor, who can determine if this type of specialized testing is needed.
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