An Electroretinogram (ERG) is an eye test that evaluates the function of the film (retina) that lines the inside of the eye.
The processes that start vision take place in the retina. The retina converts light to small electrical signals that can be sent to the brain. The retina is the most metabolically active tissue in the body. The ERG test helps diagnose diseases limited to the retina, and also diseases that affect parts of the body other than the eye.
How the test works
The idea of the ERG test is that when flashes of light come to the eye, the rods and the cones and the other cells in the retina make tiny amounts of electricity. If we know exactly how much light comes to the eye, and how much electricity comes out, we can figure out how the cells, including the rods and the cones, are working. To pick up the electricity that the retina makes, contact lens like electrodes are placed on the surface of the eye.
What happens during the test
It may not be possible for a child to hold still for the contact lenses and flashes of light. For these children, the ERG may be best done under anesthesia. The anesthesia doctors determine the appropriate anesthesia. Depending on your child's medical condition, it may be important to have a pre-anesthesia consultation with the anesthesia doctors.
To prepare for the ERG test, drops will be placed on your child's eye to dilate the pupils (enlarge the black spot in the middle of the eye). These drops are the same drops that eye doctors routinely use for examination of the eyes. Another important preparation is to have the eyes well adjusted to darkness. This is accomplished by covering the eyes with eye patches.
As with the use of any contact lens, there is a risk of scraping the surface of the eye; this is called a corneal abrasion. We take a number of precautions to minimize the risk of abrasion and it is unlikely that an abrasion will occur. In the event that an abrasion occurs it will be treated promptly. In the recovery room, it is important that your child not rub his/her eyes as this too will help minimize the risk of abrasion.
How long it takes
The time in the operating room is approximately one hour. This includes time to establish the anesthesia, the ERG test, the examination of the eyes and reversing the anesthesia. The actual ERG test time is 20-30 minutes.
Immediately after the test, some information about the results is available. We will convey this to you. However, the final report depends on measurement and analysis of the ERG records. We will send a copy of the ERG report to you and also to any physicians designated by you.
For more information
We are happy to discuss the reports with you and your child's other physicians. We are glad to discuss the ERG test with you and answer questions. Please contact us at (617) 355-5685, if you have any questions prior to the visit.