Peripheral Vision Loss
Peripheral Vision Loss
Peripheral vision loss is loss of the range of view or field that allows a person to see movement and objects out of the central line of sight. The effect is a constricted or tunnel-like range of vision. Sometimes peripheral vision loss is referred to as tunnel vision.
The normal human field of vision extends from side to front ahead to the other side to include about 160° when a person looks straight ahead. It also extends up about 60° (above the horizontal line of the eyes) and extends down about 75°. The macula at the center of the retina is mainly responsible for sharp infocus color vision at the center of the field of vision. The edges of the retina are populated mainly with rod cells that do not detect color but are excellent at detecting motion. Rod cells are mainly responsible for night vision and peripheral vision. Peripheral vision loss occurs when there is damage to the rod cells at the edge of the retina or when nerve impulses from these cells are not relayed or processed in the brain. Often people do not notice mild loss of peripheral vision; their central vision remains sharp and they compensate by turning the head more to see to the side. When peripheral vision is lost, the individual loses the ability to see motion and objects “out of the corner of the eye.”
Tunnel vision is a term used to describe the vision of people whose field of vision is 90° or less. The individual has sharp central vision but little side vision, giving the sensation of viewing the world through a narrow tunnel. In severe cases, the field of vision can be restricted to as little as 5°, and some of the diseases that cause tunnel vision can progress to complete blindness. (Occasionally, tunnel vision or other loss of part of the field of vision can be a temporary part of a migraine attack. Also, some forms of stroke can include loss of some section of the visual field. These types of losses are not discussed here.)
Congenital (present at birth) tunnel vision can develop in young children, but most people lose their peripheral vision gradually as they age. Glaucoma , which develops slowly in individuals older than age 50, is the number one cause of peripheral vision loss and the number two cause of blindness in the United States. About 1 to 2% of Americans develop glaucoma. Retinitis pigmentosa is the second most common cause of peripheral vision loss. With this group of inherited eye disorders people begin to lose their peripheral vision any time from their late teens to their early forties. Retinitis pigmentosa occurs in about 1 of every 4,000 Americans, although it is more than double that among the Navajo. Worldwide the rate is about 1 in 5,000.
Causes and symptoms
The most common causes of impaired peripheral vision are glaucoma and retinitis pigmentosa. Less common causes include:
- inadequate blood supply to the eye
- inadequate blood supply to the optic nerve
- choroideremia, an inherited eye disorder
- gyrate atrophy, a metabolic disorder related to defective creatine synthesis
- inflammation of the optic nerve (optic neuritis)
- pituitary tumor
Usually loss of peripheral vision occurs gradually in both eyes, and the loss is symmetric; that is, the field of vision narrows equally in all directions. Many people do not notice this loss until they either have a diagnostic field of vision test or the loss becomes severe. Abrupt, asymmetric loss of peripheral vision or loss in only one eye may be caused by diabetic retinopathy or partial retinal detachment . These conditions may indicate a medical emergency, and the individual should partial see an ophthalmologist immediately.
QUESTIONS TO ASK YOUR DOCTOR
- What is the cause of my peripheral vision loss?
- Can it be slowed or stopped?
- Is the loss so great that I should stop driving?
- Is it likely to progress to blindness?
- Are there any special aids that will help me make the most of the vision I have?
- Do I need a referral to a specialist?
The most common and complete way to measure the field of vision is by perimetry. The patient covers one eye and stares into the center of a half sphere (a perimeter). Points of lights appear at random around the sphere. Individuals being tested click a button every time they see a spot of light. This information is then used to map the field of vision. The procedure is repeated with the other eye. The process is painless and takes about five minutes.
If the field of vision is reduced, the eye care professional may need to do other tests to help determine the cause. These tests can include measuring intraocular pressure to diagnose glaucoma and dilating the eye and examining the internal structures with devices such as a slit lamp or ophthalmoscope. Depending on the findings, individuals may be referred to a neurologist (for nerve problems), vascular specialist (for blood vessel problems), or a retinal specialist (for diabetic retinopathy or retinal detachment).
Treatment depends on the cause of the vision loss. Most peripheral vision loss cannot be reversed, although in some cases it can be stopped or slowed. Individuals with severely restricted but symmetric field of vision in both eyes may benefit from special prismatic field-expanding glasses that help expand the field of vision. An extensive discussion of these visual aids and who can benefit from them can be found at the National Institute for Rehabilitation Engineering, which is listed in the references to this entry.
Diabetic retinopathy —A complication of diabetes in which the blood vessels of the retina leak and cause permanent vision loss.
Glaucoma —An eye disorder caused by damage to the optic nerve resulting in vision loss. Glaucoma is usually accompanied by inflammation and increased pressure in the eye (intraocular pressure). There are several types that may develop either suddenly or gradually.
Macula —The sensitive center of the retina that is responsible for detailed central vision.
Retina —Light-sensitive tissue on the back of the eye that receives images and converts them into nerve impulses to be sent to the brain by way of the optic nerve.
Retinitis pigmentosa —A group of inherited disorders that affect the rod cells of the retina. Retinitis pigmentosa begins with loss of night vision, followed by gradual loss of peripheral vision, the development of tunnel vision, and finally blindness.
Peripheral vision loss due to glaucoma can often be stopped by treatment once glaucoma is diagnosed. Because most people with glaucoma do not perceive that they have the disease until a serious amount of peripheral vision loss has occurred, it is important to have a complete eye examination every two years between the ages of 40 and 60 and every year after age 60. During a complete eye examination, the eye care professional measures the pressure in the eye. A high intraocular pressure reading can indicate glaucoma. Vision loss due to retinitis pigmentosa cannot be stopped, but with treatment it can be slowed. Other outcomes depend on the cause of the vision loss and the general health of the individual.
Loss of peripheral vision typically cannot be prevented, although in many cases it can be slowed.
Peripheral vision loss usually occurs gradually and may not be noticeable so long as central vision remains sharp. However, peripheral vision loss can affect driving safety. When the field of vision is reduced to 30° or less, even walking becomes unsafe. Caregivers should be alert to signs that the persons in their care are experiencing vision loss. Caregivers may notice their patients are walking into walls or furniture or are turning their heads more often to compensate for a smaller field of vision. Caregivers should be responsible for scheduling and providing transportation to regular vision examinations even when there are no symptoms of vision problems.
Kitchen, Clyde. Fact and Fiction of Healthy Vision: Eye Care for Adults and Children. Westport, CT: Praeger, 2007.
Haddrill, Marilyn. “Ten Warning Signs of Age-Related Eye Problems.” All About Vision. September 2007 [cited April 1, 2008]. http://www.allaboutvision.com/over60/warning-signs.htm.
Heiting, Gary. “How Your Vision Changes as You Age.” All About Vision. February 2008 [cited April 1, 2008]. http://www.allaboutvision.com/over60/vision-changes.htm.
AmericanOptometricAssociation, 243 N.LindberghBlvd., St. Louis, MO, 63141, (800) 365-2219, http://www.aao.org.
EyeCare America, The Foundation of the American Academy of Ophthalmology, PO Box 429098, San Francisco, CA, 94142-9098, (877) 887-6327, (800) 324 3937, (415) 561-8567, [email protected], http://www.eyecareamerica.org.
Tish Davidson A. M.