The area within which objects can be seen by the eye without moving the head or the eye. Each eye has its own visual field. Human vision is normally best at the center of the visual field, because images from that region fall on the fovea, an area of the retina that has the highest concentration of light receptors and the highest resolution. We generally also have some degree of peripheral vision, although objects in the periphery are seen in much less detail.

Stroke, head injury, and diseases of the eye can change the visual field. For example, brain injury caused by stroke or trauma can result in hemianopsia (blindness in half the visual field). (Changes to the visual field resulting from brain injury don't reflect damage to the eye, but rather are due to changes in the brian's ability to process visual information.) Glaucoma and retinitis pigmentosa are eye diseases that can cause loss of part of the visual field. In extreme cases, all peripheral vision can be lost, resulting in tunnel vision.

Ophthalmologists will perform a rough test of the visual field by asking you to focus on something directly ahead while they move their hand in from the sides, top, and bottom, and ask you to say when you first see their hand. Fancier tests can be performed using special equipment. In the automated perimetry exam, you sit facing a white hemispherical screen while a computer flashes small points of light on the screen, and push a button anytime you see one. This test results in a map of the visual field, showing any holes or loss at the edges.

Log in or register to write something here or to contact authors.