Humphrey visual field analyser

The Humphrey visual field analyser is arguably the world’s gold standard in visual field equipment and is used in most hospital eye departments including Addenbrooke’s.

A visual field test measures your peripheral vision. It is a painless test that doesn’t involve the use of eye drops. With your head in a static position lights are flashed on and off and you are required to react by pressing a button whenever you see a light. The lights are a mixture of bright and dim at different stages of the test. Some of the flashes are just to check you are concentrating. Each eye is tested separately, and you should allow about 15 minutes to have the whole test. The recommendation for a test is advised at your standard eye exam. It is one of the most important tests for glaucoma as it determines whether you have lost any of your peripheral vision.

The central part of the retina has the sharpest vision, whereas the peripheral areas of the retina see less clearly and are less sensitive to light. These central and peripheral areas of our vision together are known as our visual field. The ganglion cells which make up the optic nerve are receptive to a particular part of the visual field and responsible for transmitting information to the brain. Damage to any of these ganglion cells will result in that part of the visual field being less sensitive to light.

 

Glaucoma is a process by which the optic nerve cells can become damaged and die, at least partially due to the pressure within the eye. Although there are millions of these cells, one can lose up to 40% of them before being aware of any visual loss.

The visual field test is only part of a glaucoma evaluation. If only the visual field were used to diagnose glaucoma, optometrists would miss most early stage glaucoma. The visual field is used to help diagnose and categorise glaucoma, to help plan treatment, and to establish a baseline for future comparison. If an optometrist suspects a person may have glaucoma, a visual field test may help confirm or rule out glaucoma as the cause. In the later stages of glaucoma changes in the optic nerve become hard to detect, the visual field provides key information about whether the glaucoma is stable or progressing.