|
|
Visual Field Testing Can Reveal Many Eye Problems
What is visual field testing?
Visual field testing checks the whole scope of your vision for blind spots. Many times, patients with blind spots do not notice them, especially if they are in the peripheral (side) vision and not the central field of vision. Such blind spots can be caused by a number of different conditions, some of which can be very serious if left untreated. The location of the blind spot(s) can often help the doctor determine which disease is causing the problem.
What conditions can it detect?
Visual field testing is frequently used for patients with glaucoma, to test for damage to the optic nerve from the disease. The test can also reveal diseases of the retina (the light-sensitive membrane that lines the back of the eye), such as macular degeneration, retinal detachment, and retinitis pigmentosa. Problems caused by tumors in the eye or optic nerve, drooping of the eyelid (ptosis), and damage caused by an eye injury can also be detected.
Blind spots in the visual field are not only caused by eye disorders; sometimes the origin of the problem is in the brain, such as a tumor or damage from a stroke, or the cause is a systemic disease such as diabetes, hyperthyroidism, hypertension, multiple sclerosis, or a disease of the pituitary gland.
How is it done?
There are several different ways to do visual field testing. One very common, but crude, method is called the confrontation visual field exam. During this test, the doctor will sit or stand directly in front of you, and one of your eyes will be covered. You will be asked to fixate on the doctor with your uncovered eye, while he or she holds up different numbers of fingers off to the side. You will be asked when you can see the doctor's hand, and how many fingers you can see with your peripheral vision. The doctor will do this a few times, holding his or her hand in different places to test different areas of your visual field, and will then repeat the process for the other eye.
There is also the Goldmann field exam. During this test, you will sit approximately 3 feet from a screen which has a target in the center. You will be asked to stare at this target and let the examiner know when you can see an object that is brought into your peripheral field of vision.
The Amsler Grid, shown here smaller than actual size, is one method of testing your visual field.
Another low-tech method of visual field testing is the Amsler grid. Unlike the two methods discussed above, this exam tests your central vision, not your peripheral vision, for defects. You will be given a black and white grid of squares with a black dot in the center, and will be asked to hold it the same distance from your face as you would any reading material. One eye will be covered, and you will stare at the dot in the center of the grid, taking note of part of the grid which appears distorted in any way. This may include wavy or blurry lines, blank areas, dark areas, or areas where the squares do not appear to be the same size.
More sophisticated methods of visual field testing include:
Automated static perimetry - This test is computer-controlled to get more detailed and accurate results. For this exam, your head will be held still in a chin rest, usually in front of a device that looks like a white bowl. You will stare ahead at a small light in the center of the bowl, directly in front of you, while the device flashes lights in different areas of your peripheral vision, with varying intensities. You will be asked to indicate when you see these lights, usually by pressing a button.
Frequency doubling analysis - During this test, you will sit in front of a screen, where vertical bars of contrasting colors are quickly flashed. This test relies on an optical illusion: if the bars are flashed fast enough, they will appear to double in number. If you are unable to see the vertical bars or are otherwise unable to experience the illusion, that could indicate certain eye problems, such as glaucoma.
Testing relies on patient cooperation
One of the problems with visual field testing is that the results are only as accurate as the patient allows, unlike something like a blood test, which is not subjective. If you will be undergoing visual field testing, try to schedule your appointment for a time you will not be tired. Fatigue can cause you to be distracted and miss things you otherwise would have seen. Also be sure that you listen carefully to all instructions given by the examiner, so that you will respond appropriately during the test.
If you believe you are experiencing blind spots or other problems with your vision, see your eye doctor as soon as possible for a complete exam. Many eye diseases worsen over time and can cause permanent vision loss if not properly treated immediately.
Related Articles:
Learn more about visual field testing and blind spots on our forums!
Bookmark This Page
|
|
