Glaucoma Associates of Texas

Glaucoma Eye Doctor, Specialty Ophthalmologists

Dallas214-360-0000 • Plano972-612-9522 • Fort Worth817-923-2000
Rockwall469-769-1606 • Sherman214-360-0000
Southlake 214-360-0000

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Visual Field Test

visual field definition
Visual Field Examination

In glaucoma testing a visual field test is performed to measure peripheral (side) vision or visual field to determine if there is damage from glaucoma. One may have glaucoma and not be aware of it. In most individuals, there is no sudden change, which signals either the onset or progression of glaucoma. As the nerve fibers in the optic nerve (the cable that transmits the visual message from the eye to the brain) are damaged in glaucoma, there is a gradual and painless loss of vision. Initially, glaucoma affects peripheral (side) vision (Figure 1). The loss often goes unnoticed. However, if untreated, glaucoma may eventually affect central vision, as well. Usually it is only with this more advanced stage of glaucoma that one can recognize loss of vision without special tests.

An example of a visual field examination, in an eye with glaucoma. This test is performed to measure peripheral (side) vision or visual field. With this test, the visual field looks like a map. Light areas are those which are seen best. Dark areas are seen poorly.

“Initially, glaucoma affects peripheral (side) vision… if untreated, glaucoma may eventually affect central vision.”

What Is A Visual Field?

The term visual field refers to the area of a scene you can see with your eyes fixed on one location. For example, while watching a stop light, you may notice a car pulling up beside you in the next lane. Your peripheral vision enables you to see the movement of the car. The visual field is quite extensive when both eyes are working properly (Figure 2), but with glaucoma, the field of view is reduced.

How Is The Visual Field Measured?

perimeter
Perimeter
Most ophthalmologists measure the visual field using an instrument called a perimeter. To take the visual field test, you are seated with your head in a chin rest to maintain a stable position. The person giving the test will then request that you look straight ahead at a small steady light and not move your eyes.

While looking at this steady light, small white lights are flashed on and off around it (above, below, or to the side). These flashes occur one at a time. The location of the test lights corresponds to locations on the retina. The retina is the light-sensitive film, which lines the inside of the eye. All fibers in the optic nerve, including the ones, which are damaged in glaucoma, originate from the retina.

With both eyes working properly, the visual field is extensive (top), but as glaucoma worsens, the field of view can be reduced (middle) until it appears as if you are looking through a tunnel (bottom).

bad vision from glaucoma
Glaucoma Tunnel Vision

When a light flash is seen, you press a button, which in turn, signals a computer. A computer keeps track of your responses and adjusts the flashes by making them brighter or dimmer at each location tested in the visual field.

The purpose of the visual field test is to determine how bright a flashing light must be at each particular location in order to be seen. In every test, there will always be some flashes, which are too dim for even normal eyes to see. Results obtained from the test are compared to what is known about visual field tests in normal eyes. In general, the ability to detect these flashing lights is reduced at characteristic locations in glaucoma. In other words, the lights need to be brighter before they can be seen.

“In every test, there will always be some flashes which are too dim for even normal eyes to see.”

Advice For Taking A Visual Field Test

There are several things you can do to be sure you are giving the most accurate responses to the test:

  1. You should be well rested. If you are tired or ill, you should ask your ophthalmologist if the test should be postponed.
  2. You should make sure you are seated at the perimeter as comfortably as possible. The tests often take 15 minutes to complete in each eye; so comfort is important. Let the person giving the test know if you feel hunched over or if the chin rest is too high.
  3. You should always look at the target light. The location of the test lights during the test corresponds to locations on your retina. If you do not look around, your ophthalmologist can more accurately determine from the visual field where damage has occurred.
  4. You should let the technician know if you need to take a break in order to scratch your nose, cough, or take a rest.
  5. Do not be concerned if you do not see all the lights. With every test, there will be lights that even someone with normal vision will not be able to see.

What Does The Visual Field Test Tell Your Ophthalmologist?

When your ophthalmologist looks at the map of your visual field, they are looking for areas that are less sensitive to light than what is found in a healthy eye (Figure 4). Certain areas of the visual field are more often affected in glaucoma (Figure 5). These can help your ophthalmologist to diagnose glaucoma and start early treatment.

 healthy eye,  visual-field-test
Visual Field in a Healthy Eye

If you have glaucoma, and some loss of visual field is present, you will be followed carefully with repeated testing to determine if the problem has been halted or if further loss is occurring. With further loss of visual field, you often will require additional treatment. The time interval between visual field tests depends on many different factors, and is best determined by your ophthalmologist.

This ongoing and repeated testing is very important for the proper management of your glaucoma.

In a healthy eye, the central portion of the visual field corresponds to the area of best vision. On the left, the numbers tell how bright the test lights had to be in order to be detected. Higher numbers indicate better vision. On the right, the visual field map shows the lightest areas (best vision) are in the center, with some reduction in sensitivity in the periphery, even in the normal field. The darkest area corresponds to the normal blind spot.

The glaucoma eye shown here required more light than normal in all areas of the field. The numbers on the top are lower, indicating poorer vision. The visual field map (bottom) is much darker than normal, especially in the peripheral areas.


For more information on the Visual Field, please contact the Glaucoma Assocaites of Texas at 214-360-0000.

visual field map (bottom) is much darke
Glaucoma Visual Field

Sherman Office Now Open

Glaucoma Associates of Texas (GAT) would like to welcome you to our new GAT Sherman Office located in Sherman, Texas. We are excited to announce that this is our fifth office in the Dallas-Fort Worth metropolitan area. Our goal is to bring glaucoma specialists closer to your area.

Our Mission

Glaucoma Associates of Texas, Dallas, Plano, Fort Worth and Rockwall

The doctors at Glaucoma Associates of Texas (GAT) are ophthalmologists specializing in the medical, laser, and surgical treatment of glaucoma and cataracts. Each of our physicians has completed a clinical glaucoma fellowship, gaining extensive … Glaucoma Specialists

Our Video Gallery

GATT (Gonioscopy Assisted Transluminal Trabeculectomy)

Welcome to the Glaucoma Photo Gallery and Video Gallery for Glaucoma Associates of Texas! Glaucoma Video Gallery In our first video, Dr. Davinder Grover is interviewed by Cheryl Guttman Krader of Ophthalmology Times. The article about GATT … Video Gallery

Our Charity – Cure Glaucoma

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Glaucoma Associates of Texas   Cure Glaucoma, a charitable foundation, was established in 2014 by ophthalmologists at Glaucoma Associates of … Cure Glaucoma

Archives

Latest GAT News

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December 10, 2017 By Matthew Emanuel, MD

Click Here to watch Dr. Davinder Grover discuss how glaucoma-trained … [Read More...]

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December 2, 2017 By Matthew Emanuel, MD

Click Here to see Dr. Tosin Smith's recent interview on 7 Ways to Make the … [Read More...]

Living With Glaucoma

  • Living with and Managing Glaucoma
  • Low Vision Due to Glaucoma
  • Light Sensitivity and Glare with Glaucoma
  • Nutrition, Lifestyle, and Glaucoma
  • Exercise and Glaucoma
  • Cure Glaucoma Charity

GAT Dallas Office

GAT Plano Office

GAT Fort Worth Office

GAT Rockwall Office

GAT Sherman Office

GAT Southlake Office

5 Office Locations

Dallas Office 214-360-0000
10740 N Central Expressway, Suite 300
Dallas, Texas 75231

Plano Office 972-612-9522
6000 W.Spring Creek Pkwy, Suite 110
Plano, TX 75024

Fort Worth Office 817-923-2000
417 W Magnolia Avenue
Fort Worth, Texas 76104

Rockwall Office 469-769-1606
810 Rockwall Pkwy, #1010
Rockwall, Texas 75032

Sherman Office 214-360-0000
715 E. Taylor Street
Taylor Plaza, Suite 100
Sherman, TX 75090

Southlake Office 214-360-0000
305 Morrison Park Drive
Southlake, Texas 76092

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