Visual Testing

Visual Field Test

A formal visual field test is performed using a computer. With this type of testing, we can document how well each eye sees both in the center and in the periphery. The test can also determine how sensitive vision is in different parts of the visual field. It also documents areas of weakness or blind spots. The results obtained during this test can be compared to other "normal" people as well as to prior visual tests performed on the same patient. During the test, you'll be asked to look straight ahead at a particular point and signal when you see an object or light appear. During this test, nothing will touch your eye and no electrodes need to be placed on your body. This test can usually be completed in less than 20 minutes.

Optical Coherence Tomography Test

The optical coherence tomography (OCT) test is used to view and measure the back of the eye region (known as the retina). This test can be used to precisely determine the thickness of the retina in various regions. A loss of thickness may signify prior damage to the nerve layer of the retina. During this test, the patient will place his or her chin on a chinrest and look into a machine. The test does not require any electrodes to be attached to the eye or scalp. The device does not touch the eye. This test can usually be completed in less than 15 minutes.

Evoked Potentials Test

Visual evoked potentials or evoked potential (EP) tests measure the speed of messages going through pathways of the nervous system. These tests may be performed to help determine if and where nerve messages are being blocked in the visual pathway. During these tests, electrodes are placed at various points on the head. To ensure a good connection of these electrodes to your scalp, we ask that your hair be clean and dry. Wash your hair the night before the test. Do not use any hairspray, gels, or other hair products before the test. Do not wear braids, hair weaves, wigs, or other hair accessories to the test. Take your normal medications on the day of the test. You do not need to fast and should eat normally the day of the test. A technician will first measure your head and apply electrodes (small metal disks) to your scalp using an adhesive gel or paste. Each eye is then stimulated by focusing on a target in the middle of a checkerboard pattern. The computer alternates this pattern and measures the speed at which this message reaches the visual center of the brain. After the recording is done, the technician will remove the electrodes and clean off the adhesive. Due to the placement of the electrodes, your hair may be somewhat disheveled. When the testing is completed you may resume your normal activity.

Visual Acuity Test

A visual acuity test detects how well you see at various distances. Looking at an eye chart about 20 feet away, you will read aloud the smallest letters you can see. First, you will attempt to read with one eye covered, and then switch to the other. The results can help assess disease progression or response to treatment, and may reveal a need for low-vision aids.

Further testing may be needed. In this case, the eyes can be dilated by placing drops in each eye to widen the pupil. Thus, allowing more light to enter the eye. A magnifying lens is then used to examine the back of the eye, including the retina (light-sensitive tissue), the macula (the central region of the retina required for straight-ahead vision), and the optic nerve. Damage to these areas may be a sign of diabetic retinopathy, glaucoma, or age-related macular degeneration.


Tonometry measures the eye's interior pressure by sending a quick puff of air onto its surface. High intra ocular pressure is a risk factor for the optic nerve damage associated with glaucoma.