Electroretinography (ERG)- Diagnosing Problems of the Retina
Electroretinography or ERG is a type of eye test used to determine if the retina is functioning properly. During this test the various cells in the retina (rods and cones) are examined. Specifically they are tested to determine their ability to react to light.
What is the Retina?
The retina captures light and images and sends these images to the brain in the form of a nerve signal. The retina creates images using light sensitive cells that are known as rods and cones. Rods are very sensitive to light and help us to see when there isnít much light available. Cones provide sharp, clear vision and the ability to see color. They require a lot of light to function properly. Both rods and cones are found in the retina.
Sometimes the retina will encounter problems. This is where the ERG test is needed. This test helps eye doctors to find and diagnose problems in the retina so that the patient can receive the treatment that they need.
Types of ERG
There are two basic types of ERG testing. One is called a simple ERG and the other a multifocal ERG. Both tests follow a similar procedure, although the multifocal ERG is looking for specific and localized abnormalities. This test takes much longer than a simple ERG.
What to Expect
If you are preparing for an ERG, knowing what to expect can make the procedure much more enjoyable and comfortable. When you schedule an ERG it is typically because your doctor thinks that you might be having problems with your retina. There are many different conditions that might be expected. Donít worry about what conditions that you might have before the test. Getting this test is important and can help you to get the treatment that you need.
Preparing for an ERG
Typically an ERG will take about an hour. This will be longer if you are having a multifocal ERG. You donít have to do anything to prepare. Everything will be taken care of once you arrive at the doctorís office.
Before the Procedure
The ERG will work best when the pupil is open, so your doctor will typically dilate, or open, your pupils before the test. To reduce pain and discomfort numbing eye drops will be used before the procedure begins. The eyes are then propped open using a simple tool known as a speculum. Then an electrode is place into each eye. The electrode is typically placed on the cornea using a device that will look and feel much like a contact lens.
During the Test
Once the eyes have been prepared, the ERG can begin. The eyes will be exposed to a variety of different lights. The electrode placed in the eye will monitor the electrical activity of the rods and cones in the eye as they respond to the light. By using these readings a doctor can determine if you have various retinal conditions. During the test you will see various flashes of light. In some ERG tests patterns are also displayed.
You wonít experience any pain during the testing. Some people find the electrode to be a little uncomfortable. Some even say that it feels like something is in the eye. You may experience slight irritation during and after the procedure, but this should fade within a few hours.
After an ERG
Once the test is completed, make sure that you avoid rubbing your eyes for at least an hour. Since the cornea has been numbed, rubbing can cause damage. There is relatively little risk associated with this procedure. Occasionally the cornea can be scratched by an ERG, but this can be easily remedied by talking with your eye doctor. Once the test results have been received and analyzed your doctor can explain the results of the test to you.
What Conditions Can an ERG Diagnose?
An ERG can be a useful tool in diagnosing a host of different eye diseases. A few of the diseases that it is looking for include retinitis pigmentosa, Usher syndrome, congenital stationary night blindness, achromatopsia, retinal degeneration and Goldman-Farve Syndrome. A vitamin A deficiency can also cause an abnormal ERG.
How Much Will My ERG Cost?
The cost of an ERG is typically covered by your insurance. If you have insurance your doctorís office should submit a claim to your insurance company for payment. Pricing can vary, but typically it costs about $150 for a Medicare patient to receive an ERG.
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