Visual field is roughly the ‘canvas’ of visual perception (the extent all-around) seen by the eyes when it is fixating on a central object. Visual field of an eye is usually tested with the other eye closed, on a perimeter or visual field analyzer. A normal visual field (central and peripheral) usually signifies normal retina, optic nerve as well its neural connections with the brain related to that eye.

Field defect/loss is wiping out of a significant part the visual field, usually from the periphery and indicates serious pathology. The major causes of visual field loss are retinal diseases, glaucoma, optic nerve pathologies (usually field defect in the diseased eye) and certain brain-related conditions (usually produce patterned visual field defects of both eyes).

A scotoma is a smaller defect in the visual field, usually noticed in the centre of the visual field. Focal retinal lesions and early glaucoma are common causes of scotomas. Field defects/scotomas may be remain undetected by a patient due to normal function of the other eye. A small normal paracentral scotoma (the physiological blindspot) can be elicited on careful testing in most individuals but it does not interfere with normal vision.