What is a visual field assessment?
Visual field assessment (test) is a really important part of your eye health examination during your appointment.
A visual field assessment examines your area of vision and how well you see within that area. It checks your peripheral (side) and central vision and gives us information about the function of your eye.
This test helps to diagnose and monitor certain eye conditions that affect the retina
(the light-sensitive layer at the back of your eye), the optic nerve (the nerve that carries information from your eye to your brain) and the visual pathway through the brain.
Visual fields can be checked by many methods. We will choose the most suitable method for your suspected or diagnosed condition.
If you use reading glasses, please bring these with you.
The most common field test for glaucoma uses a computer that is called the Humphrey visual field analyser. The computer projects a series of lights that will flash on and off, one at a time. The test tries to find the dimmest light you can possibly see.
- You need to sit comfortably with your forehead and chin against the rests.
- Keep looking straight ahead at the central stationary orange dot throughout the test.
- Test lights will flash on and off at different times and positions within the machine.
- You will be asked to look forward and press a buzzer when you see a spot of light. The spot of light appears randomly from many different angles and is altered in size and brilliance to obtain a detailed map of your vision. This will then be repeated with your other eye.
- The test is not designed to assess whether or not your vision is good enough to drive. Some lights are bright and some are dim. Don’t be alarmed if there are periods of time when you do not see any lights. This is normal.
- Let the technician know if you cannot see any lights or if they are not in focus. Try to ignore any noises and respond only to the lights.
- Blink normally. The best time to blink is right after you have pushed the button.
- Alert the technician if you need help.
In some cases you may be asked to perform a Goldmann visual field assessment. This is not computer controlled. Instead of flashes of light, you will be shown a moving target of different sizes.
The Humphrey visual field test takes about 5 to 10 minutes for each eye.
The Goldmann visual field test may take up to 30 minutes per eye.
It is important that you are sitting comfortably and can concentrate on the instructions given – this will improve the accuracy and reliability of the test. Please tell the examiner if you are not comfortable or are finding the tests difficult.
The results are available immediately after performing your test and we will be able to explain them to you.
This depends on the results of the test. If the test shows an eye condition that needs to be monitored, you may be asked to have a visual field assessment at your next eye appointment.
A repeat test can improve the reliability of the results and help to monitor any changes to your vision. A visual field test helps the ophthalmologist to check on your progress. Visual fields are regularly monitored in some clinics such as glaucoma and neurology.