Your visual field consists of 2 parts: the very centre area, which gives you, crisp vision and the side or peripheral vision which is responsible for your awareness of movement. You can still retain very good central vision but have large areas of your peripheral vision that has been lost.

Why bother with visual field tests?

Since you probably use both your eyes at all times, you may not notice any changes in one eye's visual field unless you close the other eye. The visual field examination is important to detect many diseases that affect the eye, optic nerve or brain. It provides information, which no other test can, often detecting problems at their early stages. Eye diseases such as glaucoma or optic nerve damage may affect only one eye, and initially only very small areas of the visual field. You may not know that there is a problem unless each eye's visual field is tested separately and in detail.

How is a visual field tested?

The test we use is a fixed target test. This test uses small target lights that appear bright or dim but do not move (computerised static perimetry).

You sit in a chair facing a bowl-shaped instrument. One eye is temporarily patched. You are then asked to look straight ahead at a fixed light and to watch for the target lights to appear in your field of vision. It is very important that you keep looking straight ahead as we are testing your side vision as well as your straight-ahead vision. The target lights will appear briefly in different positions all around the bowl.

If we find that part of your visual field is not as good or as sensitive as it should be, this can be indicative of a disease or problem with the visual system. This will then require further investigation, usually by an ophthalmologist.