Peripheral Vision Problems - Blind Spots, Hemianopia and Tunnel Vision
Although some people have good central vision, there are certain eye conditions which may cause them to develop problems with their peripheral or side vision, which is ‘around the edges’.
Some types of reduction in vision are sometimes called tunnel vision, which aptly describes the problem. It appears as if the person is looking at the world through a tunnel, or tube. The image is clear in the center of the visual field, but the edges of the range of vision are blurred or indistinct.
Such problems can also be caused by an eye condition called hemianopia. This is a reduction in sight or even total blindness in one half of the visual field, caused by damage to the optic pathways in the brain. With hemianopia, half the field of vision is blacked out in both the eyes. Right homonymous hemianopia is the most common type, affecting the right field of vision, but it can also affect the left field, or the upper or lower areas of vision. Those with high blood pressure or with an increased risk of a stroke are most at risk of developing this condition.
There is no treatment, either medical or surgical, for improving this condition, but sometimes it improves on its own with time. Field-expanding prism lens glasses and magnifiers may help. Vision rehabilitation specialists can help sufferers of hemianopia to maximize their existing sight with increased lighting and other devices.
A blind spot or scotoma is an area of the visual field which is obscure. It is caused by an absence of photoreceptor cells on the retina, so part of the vision is missing or ‘blind’.
Causes of Peripheral Vision Loss
All of these eye conditions may be caused by:
- Brain injury
- Detached retina
- Brain tumor
- High pressure inside the eye
- Neurological damage such as optic neuritis
- Papilledema (compressed optic nerve head)
Such a loss of vision in the outer or peripheral visual field is often linked to damage of the optic nerve, caused by glaucoma. Occlusions are ‘eye strokes’ which may damage the part of the brain where images are processed, leading to associated blind spots.
Loss of peripheral vision, whether it arrives suddenly or gradually, should be taken very seriously and treated as a medical emergency. You should see an an eye doctor for a diagnosis immediately. You may need to undergo some visual field testing to test your side vision, discover the exact blind spots, or scotomas, and find out the actual cause. Rapid treatment in the case of a detached retina may prevent any further loss of vision, but the window for intervention may be only hours.
Treatment for Blind Spots, Hemianopia and Tunnel Vision
Tunnel vision can cause problems with mobility and can make driving hazardous. If your vision has become impaired, you may need to seek advice about how to meet the legal requirements for having a valid driver’s license in your particular state.
Unfortunately, in most cases there is no simple solution to improve the eyesight, as glasses and contact lenses cannot overcome optic nerve or brain damage. If glaucoma is diagnosed, then eye drops and medication should begin immediately to prevent further permanent loss of sight, but any vision already lost is likely permanent. For those whose blind spots are caused by brain damage, there are vision therapy techniques can sometimes be used to help sufferers regain some of their lost sight, but research is still being done in this area.
An eye doctor who specializes in low vision may be able to advise on the range of special eyewear and devices which are currently available for those with tunnel vision. For example, a prism can be added to the lens of eyeglasses to expand the field of view for those with a loss of side vision.
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