What do the results of the visual field test mean?

The visual field test is a way to evaluate the peripheral vision sensitivity of an eye. It uses a very small test light that can vary in brightness. This determines how well and how far out to the side this small intensity of light can be seen. A healthy eye can see tiny, low intensity lights way out in the periphery while a diseased eye may need a very bright, larger light before it can be seen even centrally. There are normal eye results to which each tested eye is compared. 

Glaucoma, strokes or retinal disease can be some of the causes for abnormal visual field tests.