Visual Field - definition and tests

Visual Field - definition and tests

Visual Field - 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
AGE-RELATED MACULAR DEGENERATION (ARMD) DIABETES
GRAVES’S OPHTHALMOPATHY GLAUCOMA
MULTIPLE SCLEROSIS HYPERTENSION
RETINITIS PIGMENTOSA RETINAL DETACHMENT
SCLERITIS RETINOPATHY
TRAUMA TO THE EYE STROKE
tumors of the eye or BRAIN  

See also AMSLER GRID; REFRACTION TEST; SCOTOMA; SNELLEN CHART; VISUAL ACUITY.

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