A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are found in persons over age 55, but they are also occasionally found in younger people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery.
The lens of the eye is made mostly of water and protein. Clouding of the lens occurs due to changes in the proteins and lens fibers. Age-related cataracts tend to form gradually.
Cataracts may be described in a number of ways including their location and their cause:
Cortical cataract. These opacities affect the cortex of the lens, and are identified by their unique wedge or spoke appearance. This type has been shown to be related to exposure to UltraViolet radiation.
Nuclear cataract. The nucleus is the center of the lens. As the lens ages, the nucleus tends to darken, changing from its initial clear appearance to yellow, then sometimes brown. When this darkening begins to affect vision, it is termed a nuclear cataract.
Posterior capsular cataract. This often-dense cataract is located on the posterior of the lens. Due to its location, it often affects near vision more than it affects distance. This type of cataract can result from long-term use of steroid medications.
Most cataracts are age-related. However, here are a few other causes of cataracts:
Secondary cataract. Cataracts can form after surgery for other eye problems, such as glaucoma. Cataracts also can develop in people who have other health problems, such as diabetes. Cataracts are sometimes linked to steroid use.
Traumatic cataract. Cataracts can develop after an eye injury, sometimes years later.
Congenital cataract. Some babies are born with cataracts or develop them in childhood, often in both eyes. These cataracts may be so small that they do not affect vision. If they do, the lenses may need to be removed.
Radiation cataract. Cataracts can develop after exposure to some types of radiation.
When vision is clear, the lens of the eye focuses light on the back of the eye, or the retina, which transmits the image through the optic nerve to the brain. When the lens is clouded by a cataract, light scatters so the lens can no longer focus properly, causing vision problems. Especially in age-related cataracts, vision disruption can be very gradual.
As cataracts worsen, visual symptoms tend to increase in severity. However, some patients may not recognize the change in symptoms because of a cataract’s slow progression.
Cataracts—especially nuclear cataracts—can also affect one’s ability to accurately differentiate color. As proteins in the eye age, they can develop a yellow or brown tint, causing vision to appear slightly tungsten.
While this tinting may not affect the sharpness of one’s vision, it can lead to trouble with reading or determining the difference between darker colors.
Cataracts form without pain or discomfort. However, there are several key factors that might signal the formation of a cataract:
Blurred or hazy vision
The appearance of spots in front of the eyes
Colors in vision seem faded or muted, or you may have difficulty distinguishing between dark colors like navy and black
Increased sensitivity to glare or the feeling of having a film over the eyes
Double vision or multiple images (this might clear as the cataract grows larger)
A temporary improvement in near vision
Age is the primary risk factor for developing cataracts. However, there are other factors that can affect cataract development:
Diabetes mellitus. Persons with diabetes mellitus are at higher risk for cataracts, and persons with diabetes who have cataracts have higher morbidity than those without cataracts.
Drugs. Certain medications have been found to be associated with the development of a cataract and vision loss. These drugs include:
Phenothiazine or other thiazines
Ultraviolet radiation. Studies have shown that there is an increased chance of cataract formation with unprotected exposure to ultraviolet (UV) radiation.
Smoking. An association between smoking and increased nuclear opacities has been reported.
Alcohol. Several studies have shown increased cataract formation in patients with higher alcohol consumption compared with patients who have lower or no alcohol consumption.
Nutrition. Although the results are inconclusive, studies have suggested an association between cataract formation and low levels of antioxidants (e.g., vitamin C, vitamin E, carotenoids). Further study may show that antioxidants have a significant effect on decreasing the incidence of cataracts.
The biological processes of cataract formation are becoming more clearly understood, but there is still no clinically established treatment to prevent or slow the progression of cataract.
Research on the prevention of cataract has centered on risk factors and the control of diseases, such as diabetes, which are associated with some types of cataracts.
Cataract is a multifactorial disease; different factors are associated with the development of different types of opacities.
Nevertheless, a simple, low-cost and low-risk preventive strategy is to reduce exposure to sunlight, decrease or discontinue smoking, and possibly increase antioxidant vitamin intake through consumption of leafy green vegetables and/or supplements.
Cataracts can be diagnosed through a comprehensive eye examination. This examination can include procedures including:
Refraction to determine a change in eyeglass prescription
Dilated eye evaluation that allows a better view of the lens, as well as the retina
Supplemental testing, like Visual Fields, Amsler Grid, Corneal Pachymetry/Endothelial Cell Count, B-Scan Ultrasonography, Color Vision Testing, Electrophysiology, Contrast Sensitivity and/or Glare Testing, and Potential Acuity Testing
The treatment of cataracts is based on the level of visual impairment they cause. Patients with little visual symptoms may be advised to monitor for increased visual disruption and follow a regular check-up schedule.
It is important to remember that cataracts develop slowly, and regular examinations are key
Changes in one’s eyeglass or contact lens prescription can improve many of the mild or moderate visual symptoms of cataracts. Other non-surgical treatments include:
Lens tints and coatings to decrease glare
However, patients with greater visual disruption or related ocular diseases or conditions may require further treatment, including cataract surgery.
Candidates for cataract surgery are typically those whose cataracts have decreased visual acuity to a point where there is a disruption to everyday tasks like driving.
The standard for cataract surgery today is the replacement of the clouded lens with a plastic intraocular lens (IOL). The artificial lens requires no care, and should dramatically improve vision for the patient.
New IOL options include those that simulate the natural focusing ability of a young healthy lens.
It is important to discuss the benefits and risks of cataract surgery with your eye care providers. Other ocular conditions may increase the need for cataract surgery or prevent one from being a cataract surgery candidate.
In some cases, alternatives to surgery may be available.
Cataract surgery is one of the safest and most effective types of surgery performed in the United States today. Approximately 90 percent of cataract surgery patients report better vision following the surgery.
The healing process for most cataract surgery patients is completed in 8 weeks.