Humphrey Visual Fields
This is a special procedure to do perimetry, i.e., measure visual fields. It is specifically indicated in Glaucoma.
It is an automated perimetry, wherein repeated light stimulus of varying intensities appears in different parts of the field. Fields are charted on the basis of patient’s perception of these lights, while his/her eye is focused on a central spot. The results obtained from the patient are then compared with those of the age matched normal population and the amount of damage is quantified.
It is a simple, painless out patient procedure and takes only about 15-20 minutes. This test is invaluable in diagnosing, and monitoring the treatment in patients with glaucoma. A patient typically requires multiple sittings of this investigation over a period of time to monitor the progression of the disease.
It is also useful in certain neurological conditions and in some conditions affecting the optic nerve of the eye.
The visual field test is mainly used to monitor damage to the nerve fiber at the back of the eye caused by glaucoma, though other ocular conditions may also be investigated. There are different types of visual field test – your consultant will request an appropriate test for your condition. the visual field test is designed to assess the sensitivity of the eye as well as the extent of the peripheral vision.
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 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.