Most cataracts are an age-related degenerative change in the crystalline lens of the eye. New technology has improved outcomes of surgical treatment.
Cataracts are the most common cause of blindness worldwide. In the United States, cataracts lead to visual impairment more frequently than any other cause, but—since most of them are treatable—cataracts do not typically lead to permanent blindness in this country. (Congdon N, et al., for the Eye Diseases Prevalence Research Group. Causes and prevalence of visual impairment among adults in the United States. Arch Ophthalmol. 2004;122(4):477-85)
What is a Cataract?
- The lens—the primary focusing apparatus of the eye—is a transparent, elliptical, lamellar structure (similar to a tightly-packed onion) that is enclosed within a thin, clear capsule at the front of the eye.
- Aging, disease, and environmental factors reduce the circulation, plasticity, and clarity of the lens. Opacities form within the layers of the lens and, over several years, coalesce to form cataracts.
- Depending on the location of a cataract within the lens, various degrees of visual impairment may result. Cataracts that form beneath the posterior lens capsule, for example, disproportionately impair vision because the opacity is situated at a point where incoming light rays cross before proceeding to the retina.
What are the Signs and Symptoms of a Cataract?
- Gradual, painless visual blurring
- Decreased visual acuity (particularly in bright light or when reading)
- Impaired color perception
- Decreased contrast sensitivity
- Glare (especially from bright lights, such as oncoming headlights)
- Temporarily enhanced near vision (as a lens opacifies, it causes increased near-sightedness; far-sighted individuals who need eyeglasses to see close objects may experience a period of “second sight”)
- Rarely, a cataract will swell and block the drainage of fluid from the anterior chamber of the eye, causing closed-angle glaucoma and pain
What are the Risk Factors for Cataracts?
- Age (85% are age-related)
- Gender (women are affected more frequently than men)
- Corticosteroid use
- Alcohol
- Systemic disease (diabetes, autoimmune illness, etc.)
- Ultraviolet radiation (particularly UV-B)
- Smoking
- Eye trauma
(From Rosenberg E, Sperazza L. The visually impaired patient. Am Fam Phys. 2008;77(10):1431-36)
How is a Cataract Diagnosed?
- Cataracts can be detected during clinical examination in a doctor’s office. Routine examination with a hand-held ophthalmoscope will reveal most cataracts (even those that don’t cause noticeable visual impairment).
- Slit-lamp examination—usually performed by an ophthalmologist or optometrist—can provide more details about a cataract’s size and location within the lens.
How are Cataracts Treated?
- As cataracts develop, patients often require new glasses or frequent changes in old prescriptions.
- Polarized lenses reduce glare caused by cataracts that don’t yet require surgery.
- Indirect lighting during reading or other close-up work reduces pupillary constriction and maximizes vision.
- Cataracts that cause significant visual impairment (best corrected vision is <20/40 or vision is insufficient for accomplishing necessary or desired activities) are candidates for surgery.
- Modern cataract surgery involves the removal of the entire lens and usually the placement of a silicone or plastic lens to replace the optical power lost by removal of the original lens.
- Recent developments in intraocular lens technology (e.g., Rezoom or ReSTOR lenses) allow patients to see at all distances, thus reducing dependence on accessory reading glasses.
- Cataract surgery is typically performed under local anesthesia and IV sedation; patients often remain awake during the procedure, which may last 15 – 20 minutes.
- Topical herbal preparations, DMSO, and other alternative therapies have not yet shown benefit in the treatment of symptomatic cataracts.
Prevention of Cataracts
- Cumulative ultraviolet light exposure (i.e., long-term sunlight exposure) is linked to the development of cataracts. People who spend time in the sun should routinely wear UV-blocking sunglasses.
- Smoking should be avoided, as it has been associated with cataracts (in addition to a multitude of other health problems).
- Reduce alcohol consumption.
- Limit the use of corticosteroids whenever possible.
- Treatment and control of chronic disease, such as diabetes, slows the development of many eye problems, including cataracts.
- Although the Age-Related Eye Disease Study (AREDS) showed a benefit from antioxidant supplements plus zinc for patients with pre-existing age-related macular degeneration, there is not yet any compelling evidence that such supplements prevent or slow the development of cataracts. (Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled clinical trial of high dose supplementation with vitamins C and E, beta-carotene and zinc for age-related macular degeneration and vision loss. Arch Ophthalmol. 2001;119(10):1417-1436 [corrected version 2008;126(9):1251])
Cataracts are a common, treatable cause of visual impairment in the US. Smoking cessation and avoidance of exposure to ultraviolet light are the major modifiable risk factors.
The copyright of the article Cataracts in Patient Health Education is owned by Stephen Allen Christensen. Permission to republish Cataracts in print or online must be granted by the author in writing.
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