Visual Field Test (Perimetry)

A Visual Field Test, also known as perimetry, is a crucial diagnostic exam used to measure your entire scope of vision—both central and peripheral (side). This non-invasive test helps our ophthalmologists at Pristine Eye Hospitals create a detailed map of your visual field to detect any blind spots (scotomas) you may not be aware of. It plays a vital role in the early detection and management of glaucoma.

What is a Visual Field Test (Perimetry)?

Perimetry is a functional test that assesses the sensitivity of your vision across your entire visual field. During the test, you will look into a bowl-shaped instrument called a perimeter. A computer program flashes lights of varying intensity at different locations, and you simply press a button each time you see a flash. This process systematically maps your peripheral vision and identifies any areas of vision loss, which are often the first signs of glaucoma damage to the optic nerve.

Why is this test performed?

This test is essential for several key diagnostic purposes, including:

Early Glaucoma Detection: To identify peripheral vision loss, which is a hallmark sign of glaucoma, often before a patient notices any symptoms.

Monitoring Glaucoma Progression: To track changes in your visual field over time, allowing our specialists to determine if your glaucoma is stable or worsening and to adjust treatment accordingly.

Evaluating Optic Nerve Health: To assess damage to the optic nerve and visual pathways caused by glaucoma or other neurological conditions like strokes, brain tumors, or multiple sclerosis.

Screening for Other Eye Conditions: To check for vision problems associated with retinal diseases, pituitary gland tumors, or side effects from certain medications.

How to Prepare for Your Visual Field Test (Perimetry)

There is no special preparation required for a perimetry test. However, to ensure the most accurate results, we recommend you follow a few simple guidelines.

Bring your current prescription glasses or contact lenses to the appointment.

Ensure you are well-rested, as the test requires your full concentration.

Let our technician know if you are feeling tired, anxious, or uncomfortable at any point so they can assist you or offer a short break.

The Procedure: What to Expect Step-by-Step

1. You will be seated comfortably in a quiet, dimly lit room, with your chin and forehead resting against the perimetry machine to keep your head stable.

2. One eye will be covered with a patch, and you will be given a handheld button. You will be instructed to focus on a central target light inside the machine’s dome.

3. As you stare at the central light, small, dim lights will flash one at a time in your peripheral vision. You must press the button every time you see a light appear. It is normal not to see all the lights, as some are used as controls.

4. The test typically takes 5 to 10 minutes per eye. Once the first eye is complete, the patch will be switched, and the procedure will be repeated for your other eye.

Understanding Your Results

The perimetry machine generates a detailed map of your visual field for each eye. This map will be carefully interpreted by your ophthalmologist at Pristine Eye Hospitals. A healthy visual field will appear clear, while areas where you did not see the lights will show up as dark spots or patterns. These “scotomas” indicate areas of reduced sensitivity or vision loss.

The specific pattern, size, and location of these blind spots help your doctor diagnose conditions like glaucoma and determine their severity. For patients with glaucoma, we compare current results with previous tests to monitor for any changes, which is critical for managing your condition and preserving your sight.

Frequently Asked Questions