Table of Contents
Definition of Visual Field
Visual Field is the total area or scope of vision. eye care specialists map the visual field by measuring the boundaries of peripheral vision in degrees from the point of central vision. A normal field of vision is 135 degrees vertically (60 degrees up and 75 degrees down) and 160 degrees horizontally (100 degrees outward and 60 degrees inward).
Everyone has a blind spot of about 10 degrees in the direct center of vision, the point at which the optic nerve enters the retina (the optic disk). The optic disk contains no rods or cones. Binocular vision (the ability to see with both eyes) compensates for each eye’s blind spot with overlapping visual fields for each eye.
People who have monocular vision (the ability to see only through one eye) learn to accommodate for the blind spot by frequently moving the eye to scan the field of vision.
Visual Fields Test
There are several methods for measuring visual field. The simplest though least precise is for the eye care specialist to sit across from the person and, with the person looking at a fixed point the eye care specialist slowly moves a hand or an object such as a pen. The person tells the point at which he or she can see the object.
The eye care specialist may repeat this procedure several times for each eye, measuring peripheral vision from each side, above, and below. Other methods may use computerized flashing lights with the person looking at a fixed point (target) within a contained dome. The person presses a button for each light he or she sees, and the eye care specialist creates a map of each eye’s visual field that allows calculation of visual field percentages.
Conditions that can affect the visual field
|CONDITIONS THAT CAN AFFECT THE VISUAL FIELD|
|age-related macular degeneration (armd)||diabetes|
|retinitis pigmentosa||retinal detachment|
|trauma to the eye||stroke|
|tumors of the eye or brain|
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