Understanding Your Visual Field Test

Reasons for Abnormal Test Results

A visual field test
Visual field.

A visual field test is a way to measure your visual field. Your visual field is an indicator of how much you can see to each side while focusing your eyes on a central point (peripheral vision). Conducting a visual field test is called perimetry. A visual field test helps distinguish problems with peripheral vision from problems with central vision. Your eye doctor might order a visual field test as part of an annual comprehensive eye examination.

What About Results?

In many cases, your visual results will be normal. If your test results are normal, your peripheral vision is in good working order. However, if you have abnormal results, there may be a problem with your central nervous system or an undiagnosed health problem. Also, a visual field test may detect central or peripheral retinal disease, some eyelid conditions including ptosis (drooping eyelid), optic nerve disease, and diseases affecting the visual pathways within the brain. Visual pathways carry information from the eye to the visual part of the brain, where information is processed into vision. An abnormal visual field test result is a reason for concern and normally will result in more testing to uncover a possible problem.

Potential causes of an abnormal visual field test result include the following:

  • Pituitary gland disorders
  • Central nervous system problems, such as a tumor that is compressing one of the visual parts of your brain
  • Stroke

How Much Does It Cost?

Visual field testing is generally covered by health care insurance plans, although testing may be limited to one time per year for glaucoma suspects.

A glaucoma suspect is a patient with symptoms and signs that are likely to develop into glaucoma in the future. For people already diagnosed with glaucoma, insurance plans usually allow two visual field tests per year. 

How Long Does It Take?

Several methods are used by doctors to test visual field. Most visual field tests requires only a few minutes in healthy patients. More time may be needed when testing ill or elderly patients. Visual field testing can also be more difficult and time consuming in young children. 

A simple, basic visual field test is performed by having the patient look straight ahead and count the fingers shown by the doctor from each side. However, visual fields are typically measured by a computer in an optometrist's or ophthalmologist's office. For a computerized test, one eye is covered and the chin is placed upon a chin rest. The patient holds a button and when a flash of light is seen, he or she pushes the button. The process produces a computerized map of the patient's visual field.

 

Don't be alarmed if your doctor repeats your visual field test several times to ensure its validity, as there is some subjectivity in performing the test. The first time a doctor performs a visual field test, they may not know what to expect, thus invalidating the results. Repeat testing often yields normal results.

Source:

Choplin, Neil T and Russel P. Edwards. Humphrey Field Analyzer. SLACK Incorporated, 1995.

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