Peripheral visual field is defined as the extent to which an individual can see up, down, and side-to-side while looking straight ahead. A peripheral visual field test measures the visual range (horizontal and vertical) as well as the sensitivity of vision. The test indicates how much one can see around them while the eyes are fixed at one point.
A peripheral visual field test is helpful when trying to distinguish between peripheral vision issues and central vision issues. Visual field tests assess whether the vision is being affected by eye and brain function rather than eye focus.
An eye specialist may perform the procedure to detect blind spots within the patient’s field of view (known as scotoma) as well as other eye defects such as dim vision.
Also Known As
- Automated perimetry exam
- Visual field test
- Goldmann visual field exam
- Tangent screen exam
There are several techniques through which a peripheral visual field test can be conducted. However, they fall under either:
Static Perimetry- This is the most commonly used of the two, as it is an automated process. Tests that fall under this category use a blinking light signal. This light signal is introduced into various points of the patient’s visual field and the patient records when they see the light stimuli.
Kinetic Perimetry- As the name suggests, the tests that fall under this category involve a moving stimulus as opposed to blinking lights. When the patient sees the stimulus, a mark is made by the eye specialist.
The test is conducted as part of a routine eye examination at the eye clinic or the eye doctor's office by:
- An optometrist
- A neurologist
- An ophthalmologist
The most common reason for testing visual fields is for patients with diagnosed or suspected glaucoma. The test is also used to determine if someone has near-sightedness (myopia), far-sightedness (hypermetropia), drooping (ptosis), optic nerve damage and diseases, retinal detachment, and eye injuries.
Other reasons for conducting a peripheral visual field test include to test:
- Toxicity from medications which have been proven to affect the central retina.
- The course of visual field loss over time.
- Retinal diseases, such as retinitis pigmentosa.
- Conditions such as concussions, tumours, injury, poor circulation and stroke.
Preparation & Expectation
It is a simple, painless, and straight-forward exam. However, the young, ill, elderly, and mentally challenged may find it challenging to keep their gaze on just one spot or follow crucial instructions.
The test doesn't take long except in exceptional cases. Tests take anywhere between 20 and 30 minutes.
No prior preparation is required. However, if you wear glasses, take them with you to the eye specialist’s office.
Below are four common tests an eye specialist may use. S/he may decide to perform one or a combination of these. They include:
1. Confrontation visual field exam
This is a quick, preliminary way of checking the visual field without the use of a machine. The patient and eye specialist will sit directly in front of each other, about an arm's length away and at eye level. In this test, each eye is tested separately. The patient will remove any contact lenses or glasses, cover one eye with a hand and then look straight into one of the specialist's eyes.
Various targets (stationary or moving) will be presented at different points of the visual field. The specialist will then ask how well the patient can see them. This type of test falls under kinetic perimetry.
2. Tangent screen
This exam is used to develop a map of a person's visual field. The patient will sit in front of a flat, black screen with a target on it. They will stare at the target ahead and say when they can see an object (which the examiner will introduce) coming into their side vision. This exam is usually used to detect brain or nerve issues. This type of test also falls under kinetic perimetry.
3. Static automated perimetry
For this test to be conducted, the patient sits and rests their chin and forehead on a concave machine while staring at a target ahead. The patient will have a button to push when they see a small flicker of light appear. They are systematically introduced into the periphery by the machine. This test can track the progression of an already diagnosed condition. As the name suggests, this test falls under static perimetry.
4. Amsler grid
Used since 1945, this type of test uses horizontal and vertical lines which join to form a grid of equally sized squares. The patient will be required to focus at a dot at the center of the grid and say what spots appear blurry, distorted or blank. The eye specialist will then take note of these spots. Patients with age-related macular degeneration (AMD) often use the Amsler grid at home to monitor vision changes. This type of test falls under kinetic perimetry.
If the patient was able to clearly see the introduced light signals/stimuli, then this shows a positive outcome. However, if the patient noted difficulty clearly seeing introduced light signals/stimuli, this indicates that there is the possibility of a blind spot in that area or an undiagnosed health problem.
The eye specialist may opt to schedule a repeat test, even if the results are positive. This is usually to confirm the received results.
In cases where an abnormal result is presented, a repeat test may be scheduled to evaluate your vision loss. This repeat test is normally conducted between six to 12 months, depending on the severity.
When the follow-up test reveals that the disease has progressed further, change in treatment is required.
Risks & Complications
Since peripheral visual field tests are not abrasive, there are no complications associated with the test. You may resume your normal activities immediately.