Sometimes your eye condition requires visual function testing that goes beyond a general eye exam. At the University of Maryland’s Electrophysiology Laboratory, we will provide you with detailed results and offer you the latest approaches to treat your eye condition.

Our team of specialists, led by Dr. Mary A. Johnson, a vision specialist who has more than 40 years of clinical electrophysiology experience, will meet with you to learn more about your eye problems. Our team has extensive experience diagnosing rare eye diseases, using pain-free testing to make an accurate diagnosis.

Learn more about our testing location, the UM Electrophysiology Laboratory, located at UM Eye Associates at Redwood.

Visual Function Tests

Electroretinogram (ERG)

The electroretinogram, or ERG, shows abnormal function of the retina and is like an electrocardiography (EKG) for the eye.

During this test, we record responses from the nerves in the eye, which gives us very sensitive information about how the eye is working.

While the actual test only takes a few minutes, we will need time before the test to dilate your pupils and let your eyes adjust to the dark.

We will put some numbing drops in your eyes then place contacts on your eyes. We will flash several different types of lights for a few minutes, usually recording results from both eyes at the same time.

This total time for this process is about one hour.

Visual Evoked Potential (VEP)

The visual evoked potential, or VEP, measures how information from the eye gets to the brain. For this test, we paste wires on the front and back of your head. You will look at a television screen that shows black and white checks. If you wear glasses, please be sure to bring them with you. This test takes approximately one hour to complete.

Electro-Oculogram (EOG)

The electro-oculogram, or EOG, measures how well a layer of cells supporting the retina is working. In this test, we paste wires on either side of each eye and have you look at two lights that are alternating back and forth. You will look at these lights for the first 15 seconds of every minute for 35 minutes. This test takes about one hour to complete.

Color Vision Tests

We do a variety of color vision tests. All involve sorting caps with different colored tops. The Farnsworth-Munsell 100-hue color vision test takes between 30 minutes and an hour for most people.

The desaturated Lanthony D-15 test and Roth-28 test are much shorter, each taking 15 to 30 minutes.