Visual Field Test (HFA)

What is Visual Field /HFA?

Visual field test, also known as perimetry, is a diagnostic procedure that can find out problems in central and peripheral vision. It measures the field of vision seen by the eye. This helps evaluate how well the retina detects light stimuli at different positions. This is measured when the patient is looking at a single point in front of them.

HFA or Humphrey Field analyzer is a medical device used to map the visual field. It will project light of different intensities onto a bowl and measure the patient’s ability to see it.

What is the test used for?

A visual field test is used to detect and monitor different eye diseases and neurological conditions. These include conditions such as glaucoma, which is a condition that affects the optic nerve and leads to peripheral vision loss, which can be detected through a visual field test.

Some other conditions that can possibly be diagnosed include pituitary disease, that impacts vision, brain tumors, macular degeneration, which is characterized through blind spots in the central vision, or other neurological deficits.

It can help track the progression of conditions such asmultiple sclerosis, Brain Tumours, strokes and other neurological conditions causing visual field loss .

What is the procedure for doing HFA?

Seat the patient in front of the HFA machine with their chin on the chin rest and forehead against the forehead rest.
One eye at a time is tested; the other eye is covered with an eye patch.
The patient is asked to fixate on a central target.
The HFA machine presents visual stimuli (light of varying intensities) at different areas of the visual field.
Patients press a trigger button whenever they see the light.
Based on the patient's responses, the test will automatically adjust the light intensity and location of the light stimuli to increase the duration and accuracy of the test
The test typically takes 15 to 20 minutes per eye, depending on the type of test and the patient’s learning curve.

What is a normal visual field?

With a normal visual field, the eyes can see a wide area of space in front of them. This is the central vision. Without moving their eyes, patients should be able to see not only in front of them, but up, down, and to the side. This is called peripheral vision.

When should a visual field test be performed?

A visual field test is prescribed when the treating doctor suspects a condition like Glaucoma or a neurological disease which could affect the field of vision. This can help the patient’s eye care provider find early signs of any diseases or conditions that may present.

How many times should a visual field test be performed?

Sometimes a visual field test may need to be repeated to check if the results are accurate. Sometimes the results may be unreliable if different factors are impacting the vision, such as being tired. Otherwise, visual field tests will be performed annually at every eye exam to make sure that there are no new problems. With certain eye conditions, the test may be performed more frequently to track its progression.

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