What is a visual field test?
Visual field testing is most frequently used to detect signs of glaucoma damage to the optic nerve. In addition, visual field tests are useful for the detection of central or peripheral retinal diseases of the retina, eyelid conditions such as drooping (ptosis), optic nerve damage and disease, and conditions affecting the visual pathways from the optic nerve to the area of the brain (occipital cortex) where this information is processed into vision.
The following are uses of visual field testing:
- Screening for glaucoma: Peripheral vision loss is often an early and subtle sign of glaucoma. Visual field tests are helpful in detecting vision loss and making the diagnosis of glaucoma, and repeat testing is used to monitor treatment.
- Screening and testing for lid droop (ptosis)
- Testing for toxicity from certain medications (for example, screening for toxicity from hydroxychloroquine [Plaquenil], which can affect the central retina)
- Measuring the extent of retinal diseases, such as retinitis pigmentosa
- Detecting conditions affecting the optic nerve, such as tumors, injury, poor circulation or stroke, optic neuropathy, swelling of the optic nerve (optic neuritis), compression from swelling in the eye socket or orbit, and severe nutrient deficiencies
- Detecting conditions that affect the visual pathways from the optic nerves to the occipital lobe of the brain, including tumors, inflammatory disease, increased intracranial pressure, injury, poor circulation, or stroke
- Testing for malingering behavior or factitious disorders
How is a visual field testing procedure performed?
There are a variety of methods to measure the visual fields. During an eye exam, visual field testing is performed one eye at a time, with the opposite eye completely covered to avoid errors. In all testing, the patient must look straight ahead at all times in order accurately map the peripheral visual field. Most modern visual field testing devices also continuously monitor fixation, or the ability of the patient to maintain a consistent straight ahead gaze.