The visual field is the total area in which objects can be seen in the peripheral vision while the eye is focused on a central point.

Confrontation visual field exam: A quick and basic evaluation of the visual field done by an examiner sitting directly in front of you. With one eye covered, you are asked to look at the examiner's eye and tell when you can see the examiners hand.

Tangent screen or Goldmann field exam: You will be asked to sit about 3 feet from a screen with a target in the center. You will be asked to stare at the central target and let the examiner know when you can see an object brought into your peripheral vision. The extent of your peripheral vision is mapped.

Automated perimetry: You sit in front of a concave dome and stare at a central target within the dome. A computer-driven program flashes small lights at different locations within the dome's surface, and you press a button when you see the small lights in your peripheral vision. Your responses are compared to age-matched controls to determine the presence of defects within the visual field.

No special preparation is necessary for these tests.

There is no discomfort with this test. Some visual field tests take a long time and may be tiring.

The test will detect any loss of peripheral vision and provide a map of that loss which will be helpful in diagnosing the cause.

The peripheral vision is normal in extent.

Abnormal results may indicate diseases or central nervous system problems such as tumors that damage or compress the parts of the brain that deal with vision. Other diseases that may affect the visual field of the eye include diabetes, hyperthyroidism (a condition where the thyroid produces an excess of hormones), hypertension, diseases of the pituitary gland, and multiple sclerosis.

Additional conditions under which the test may be performed:

• Glaucoma
• Optic glioma
• Stroke
• Stroke secondary to cardiogenic embolism
• Stroke secondary to carotid dissection
• Stroke secondary to cocaine

The test has no risks.

The type of visual field testing to be done will be discussed with you by your doctor.