Peripheral Visual Field Testing (Perimetry)
Peripheral Visual Field Testing (or a "Field Test" for short) is a very useful and accurate way of assessing someone's peripheral vision.
The test is performed by looking into a bowl-shaped curved screen. Small spots of light are projected onto the screen, and you will be asked to press a button every time you see one of these spots. The spots of light appear randomly in all directions, and are of varying brightness. Our orthoptists will guide you through the test and give you all the instructions. Performing the test well requires a good amount of concentration, and the test usually takes about 5 minutes to complete.
Visual field testing is mainly used in the diagnosis and management of glaucoma.
Glaucoma is a disease of the optic nerve that can result in vision loss. This peripheral vision is affected first, and so visual field testing is important as it can pick up subtle loss of vision in the periphery long before the person notices any change to their central vision.
Visual field testing is also used in the diagnosis of other conditions such as:
- Retinal diseases such as retinitis pigmentosa
- To screen for "Plaquenil maculopathy". Plaquenil is a drug used to treat autoimmune diseases such as lupus and rheumatoid arthritis. One potential side-effect of plaquenil is toxicity to the retina, and visual field testing can help to look for this.
- Diseases of the optic nerve, such as optic neuritis or ischaemic optic neuropathy.
- Neurological diseases can also cause loss of peripheral vision, such as stroke, multiple sclerosis and brain tumours.
Visual field testing is also an important part of assessing someone's safety to drive, which is compulsory for anyone over 75 years of age.
