Hyperopia is one of several eye conditions called refractive errors, which means that light entering the eye is not properly focused on the retina (the light-sensitive layer of tissue at the back of the eyeball). It is not a disease of the eye in the strict sense.
Hyperopia, or farsightedness, is a condition that develops when a person's eyeball is abnormally short from front to back, or when the cornea (the clear front portion of the eyeball) is abnormally flat. In a normal eye, light entering the eye through the cornea is focused by the lens of the eye on the retina. In hyperopia, the abnormal shortness of the eye or the flatness of the cornea causes the lens to focus images behind the retina. This incorrect focus means that objects at a distance can be seen more clearly than those that are close to the viewer. If the hyperopia is severe, the person may be able to see clearly only objects that are quite far away.
Hyperopia is a common refractive error in the general population, affecting about 25 percent of the general population. In addition, the condition tends to run in families. Hyperopia is often combined with astigmatism, another type of refractive error caused by irregularities in the curvature of the cornea or the lens of the eye.
Most babies are mildly hyperopic at birth. Hyperopia in children is usually less severe than hyperopia in adults, partly because the eyeball in many children lengthens as they grow older and allows the eye to focus
normally. It is thought that between 6 and 9 percent of children in the United States may have mild hyperopia. Boys and girls are equally affected. There are, however, racial and ethnic differences, with Native Americans, African Americans, and Pacific Islanders having higher than average rates of hyperopia.
There is a condition similar to hyperopia called presbyopia that appears in middle-aged adults. Presbyopia is a type of farsightedness that develops because the lens of the eye becomes less flexible with age and cannot change its shape as easily when the person is trying to focus on near objects (usually reading materials). Most people over forty will develop some degree of presbyopia. Hyperopia that went unnoticed during a person's younger years may become apparent in middle age, when the person begins to develop presbyopia as well.
In addition to a short eyeball or flatter cornea, hyperopia can be caused in some people by abnormal development of the eye or by trauma to the eye. In a very few cases, hyperopia may be related to disorders of the nervous system or to medications that affect the eye's ability to focus. In general, genetic factors are thought to play a more important role in hyperopia than environmental factors or personal history.
Hyperopia in younger children may not cause noticeable symptoms. Older children and adults, however, will often develop the following symptoms:
- Having to squint while reading.
- Frequent blinking and difficulty focusing on close objects.
- Red or teary eyes, or burning or aching in the eyes.
- Blurry vision.
- Headaches or general discomfort in the eye after a long period of reading, writing, or doing other close work.
Preventive Eye Care
Protection of one's vision is an important part of preventive health care. Eye doctors recommend the following schedule of eye examinations for children and adults:
- Children: should have their eyes tested by their pediatrician or an ophthalmolo-gist between birth and three months; between six months and one year; at three years; and at five years.
- Older children and adolescents: should be seen yearly if they wear corrective lenses, have other eye problems, or have diseases like diabetes that affect the eyes.
- Adults between twenty and thirty-nine: should have the eyes checked every three to five years.
- Adults over thirty-nine who do not wear glasses and are at low risk of eye disease: should be checked every two years between forty and sixty-four, and every year after age sixty-five.
- Adults over thirty-nine who do wear eyeglasses or contact lenses: should have an eye checkup every year.
People who notice blurriness, pain, or any other visual problem should make an appointment with their eye doctor as soon as possible even if they recently had an eye checkup.
People who have these symptoms should make an appointment with an optometrist (an eye care professional who is trained to diagnose refractive errors) or an ophthalmologist (a doctor who specializes in
diagnosing diseases of the eye) to find out whether they need corrective lenses.
Hyperopia and other refractive errors are evaluated by a series of vision tests. After the examiner takes a history of the patient's symptoms (including a family history of eye problems), the patient is usually asked to read the letters on an eye chart. The examiner may also shine lights into the eyes or administer eye drops that allow him or her to see all the structures inside the eye clearly.
To measure the strength of the lens needed to correct the patient's hyperopia, the examiner uses a device called a photopter (or refractor). The photopter is placed in front of the patient's eyes, and the examiner moves various lenses in and out of the device while the patient reads letters on an eye chart located 20 feet (6 meters) away.
Screening for and treatment of hyperopia in school-age children is important because significant hyperopia can lead to strabismus (inability of the eyes to work together) or amblyopia, a condition in which there is poor vision in one eye that is not caused by disease. In addition, uncorrected hyperopia can lead to problems in school, including learning disorders and loss of interest in reading.
Hyperopia can be treated nonsurgically by prescription eyeglasses or contact lenses, which are prescribed by the optometrist or ophthalmologist but made and fitted by an optician. There are also surgical options for people who dislike glasses or contact lenses. The two most common surgical procedures for hyperopia involve reshaping the cornea with a laser or implanting an artificial lens in the front of the eye. Reshaping the cornea works better if the refractive error is only low to moderate. Patients with a high degree of refractive error generally do better with lens implantation.
There are drawbacks to surgical correction for refractive errors, however. These include the risks of infection, development of haze in the cornea, or dry eyes. In some cases the surgeon may need to perform a second operation if the first one either overcorrected or undercorrected the shape of the patient's cornea.
It is important for a patient diagnosed with hyperopia to discuss all the treatment options with the optometrist or ophthalmologist, as no
two people will have exactly the same degree of farsightedness or the same lifestyle.
Most patients with hyperopia do well after being fitted with corrective lenses or having eye surgery. Hyperopia caused by the shape of the eyeball or the cornea does not get worse with age and is unlikely to lead to vision loss.
Hyperopia is largely a matter of heredity and cannot be prevented. People can, however, prevent strabismus or other complications of hyperopia by visual screening in childhood and regular eye checkups at all ages.
It is possible that laser treatment and other types of vision surgery will be further refined in the future and have fewer risks or side effects.
WORDS TO KNOW
Amblyopia: Dimness of sight in one eye without any change in the structure of the eye.
Astigmatism: A refractive error caused by irregularities in the shape of the cornea or the lens of the eye.
Cornea: The transparent front part of the eye where light enters the eye.
Ophthalmologist: A doctor who specializes in diagnosing and treating eye disorders and can perform eye surgery.
Optician: An eye care professional who fills prescriptions for eyeglasses and corrective lenses.
Optometrist: An eye care professional who diagnoses refractive errors and other eye problems and prescribes corrective lenses.
Photopter: A device positioned in front of a patient's eyes during an eye examination that allows the examiner to place various lenses in front of the eyes to determine the strength of corrective lenses required.
Presbyopia: Age-related farsightedness caused by loss of flexibility in the lens of the eye.
Refractive error: A general term for vision problems caused by the eye's inability to focus light correctly.
Strabismus: A condition in which the eyes are not properly aligned with each other.
SEE ALSO Astigmatism; Myopia; Strabismus
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Freudenheim, Milt. “To Read the Menu, Baby Boomers Turn to Eye Treatments.” New York Times, April 11, 2004. Available online at http://query.nytimes.com/gst/fullpage.html?res=9A0CE3DF1138F932A25757C0A9629C8B63&sec=&spon=&pagewanted=all (accessed April 29, 2008). This is an article about the application of radio waves to the cornea of the eye to treat hyperopia.
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