Cataracts

Although there are several different types of cataracts, they are all caused by a loss of transparency in the crystalline lens of the eye. This loss of transparency causes a disruption in the transmission of light to the retina.

Cataracts most commonly occur among people who are over age 55, although it can affect younger people and, rarely, newborns. On a global basis, cataracts account for over one-half of all cases of impaired vision and affect over 20 million people.

Cataract Myths:

Cataracts do not "spread" from one eye to the other.
Cataracts are not caused from over-using eyes.
Cataracts are neither contagious nor related to cancer.
There is no known means to reverse the clouding once it occurs.
Cataracts are not a film or coating on the eye.

What causes the development of cataracts?

Chemical changes within the protein material of the lens are responsible for clouding and yellowish or brown discoloration. These chemical changes seem to be part of the natural aging process, although they may also be caused by injury, inherited tendencies, certain diseases or birth defects.

Other contributing factors include exposure of the eye to ultraviolet light (sunlight), poor nutrition, cigarette smoking and certain drugs.

How do cataracts affect sight?

The lens is normally clear so light can readily pass through it, producing a sharp image on the retina. When the lens becomes opaque, light can't pass through as easily. Having a cataract is like trying to look through a foggy window. Cataracts may affect a small portion of the lens or the entire lens, causing little or no visual problem for some people, especially in the early stages of the condition. Severe cataracts may cause a complete loss of functional vision.

The degree to which a person's vision is affected by cataract formation depends on the location and degree of clouding. For instance, if the area of clouding initially starts on the side of the lens, a person's vision may not be drastically affected because peripheral vision is not used as much as the central area. Cataracts typically develop in both eyes, although the rate of progression varies with each eye. The onset of a cataract may be gradual or rapid. Cataracts usually develop around age 50, but may not significantly interfere with sight until much later — age 65 to 75.

Can cataracts be prevented?

There is no known prevention for cataracts that occur as a natural process of aging. However, there is growing evidence that exposure to ultraviolet light (sunlight) and cigarette smoking may speed their development. Avoidance of excessive sun exposure and smoking is a sound preventive measure.

Diagnosis and Treatment

A comprehensive eye health examination is needed to detect cataract formation. After diagnosis, regular follow-up care is needed to assure the best possible correction for the level of impairment.

Prescription glasses can help. At some point, however, cataracts may become so dense that good vision can no longer be maintained with just prescription eyewear. At that time, surgery may be the best option to restore vision.

The decision regarding surgery is one that is made jointly by the patient and the eye care professional. The decision of when to have a cataract removed depends on a number of factors, such as the extent of clouding, the location of the cataract, and the extent to which normal daily activities are impaired. For instance, if reading or driving abilities are impaired, surgery may be a more realistic consideration than if such impairments have not yet been noticed.

What does cataract surgery involve?

Cataract surgery has improved dramatically in the last decade, with a very high success rate (95% or better). Over one million cataract surgeries are performed annually. The surgery has few complications and an increasingly short recovery time. Most of the time, the procedure is done on an outpatient basis.

Because only one eye is operated on at a time, the more impaired eye is usually done first. Surgery is often timed such that the other eye still has adequate vision for one to function until the surgical eye has healed.

Cataract surgery involves the removal of the clouded lens. When the affected lens is removed, focusing power of the lens must be replaced. Often, an artificial lens implant, known as an intraocular lens implant or IOL, will be inserted into the eye immediately after the impaired lens is removed. Eyeglasses and contact lenses are other forms of lens "replacement." However, since these replacements are not within the eye itself, vision is not as natural.

Sometimes cataract removal does not result in complete improvement in vision because sight is dependent on many other factors, such as the "health" of the retina, which may also be impaired. In such cases, proper eyewear can usually further enhance vision to an acceptable range.

Although no substitute is as good as the real thing — nature's own lens — the availability of replacements certainly is an improvement over earlier days when the development of cataracts simply meant a gradual, progressive loss of vision.