Thursday, December 20, 2012
Visual Field Testing
During a routine eye exam, some eye doctors may want to determine through visual field testing the full horizontal and vertical range of what you are able to see peripherally. This range is commonly referred to as "side vision."
Visual field tests assess the potential presence of blind spots (scotomas), which could indicate eye diseases. A blind spot in the field of vision can be linked to a variety of specific eye diseases, depending on the size and shape of the scotoma.
Many eye and brain disorders can cause peripheral vision loss and visual field abnormalities.
For example, optic nerve damage caused by glaucoma creates a very specific visual field defect. Other eye problems associated with blind spots and other visual field defects include optic nerve damage (optic neuropathy) from disease or damage to the light-sensitive inner lining of the eye (retina).
Brain abnormalities such as those caused by strokes or tumors can affect the visual field. In fact, the location of the stroke or tumor in the brain can frequently be determined by the size, shape and site of the visual field defect.
Types of Visual Field Tests
Confrontation visual field testing typically is used as a screening visual field test. One eye is covered, while the other eye fixates on a target object, such as the doctor's open eye, while the doctor stands or sits directly in front of you. You then are asked to describe what you see on the far edges or periphery of your field of view.
If an eye disease is suspected, you may need to undergo more comprehensive, formal types of visual field testing to evaluate the quality of your central and peripheral vision.
The picture to the right shows a patient who doing visual field testing with a Humphrey Field Analyzer (HFA), which uses automated perimetry to measure responses to visual stimuli appearing in central and side vision. (image by Zeiss) By Marilyn Haddrill; contributions and review by Charles Slonim, MD