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A cataract is a cloudy or opaque area (an area you cannot see through) in the lens of the eye.

Alternative Names

Lens opacity


The lens of the eye is normally clear. If the lens becomes cloudy, the condition is known as a cataract. Rarely, cataracts may be present at or shortly after birth. These are called congenital cataracts.

Adult cataracts usually develop with advancing age and may run in families. Cataracts develop more quickly in the presence of some environmental factors, such as smoking or exposure to other toxic substances. They may develop at any time after an eye injury. Metabolic diseases such as diabetes also greatly increase the risk for cataracts. Certain medications, such as cortisone, can also accelerate cataract formation.

Congenital cataracts may be inherited. The gene for such cataracts is dominant (autosomal dominant inheritance), which means that the defective gene will cause the condition even if only one parent passes it along. I families where one parent carries the gene, there is a 50% chance in every pregnancy that the child will be affected.

Congenital cataracts can also be caused by infections affecting the mother during pregnancy, such as rubella. They are also associated with metabolic disorders such as galactosemia. Risk factors include inherited metabolic diseases, a family history of cataracts, and maternal viral infection during pregnancy.

Adult cataracts are generally associated with aging. They develop slowly and painlessly, and vision in the affected eye or eyes slowly gets worse.

Visual problems may include the following changes:

  • Difficulty seeing at night
  • Seeing halos around lights
  • Being sensitive to glare

Vision problems associated with cataracts generally move towards decreased vision, even in daylight.

Adult cataracts are classified as immature, mature, and hypermature. A lens that has some remaining clear areas is referred to as an immature cataract. A mature cataract is completely opaque. A hypermature cataract has a liquefied surface that leaks through the capsule, and may cause swelling and irritation of other structures in the eye.

Most people develop some clouding of the lens after the age of 60. About 50% of people aged 65-74, and about 70% of those 75 and older, have cataracts that affect their vision.

Most people with cataracts have similar changes in both eyes, although one eye may be worse than the other. Many people with this condition have only slight visual changes, and are not aware of their cataracts.

Factors that may contribute to cataract development are low serum calcium levels, diabetes, long-term use of corticosteroids, and various inflammatory and metabolic disorders. Environmental causes include trauma, radiation exposure, and too much exposure to ultraviolet light (sunlight).

In many cases, the cause of cataract is unknown.


  • Cloudy, fuzzy, foggy, or filmy vision
  • Loss of color intensity
  • Frequent changes in eyeglass prescription
  • The glare from bright lights causes vision problems at night, especially while driving
  • Sensitivity to glare from lamps or the sun
  • Halos around lights
  • Double vision in one eye
  • Decreased contrast sensitivity (the ability to see shades, or shapes against a background)

Exams and Tests

  • Standard ophthalmic exam, including slit lamp examination
  • Ultrasonography of the eye in preparation for cataract surgery

Other tests that may be done (rarely) include:

  • Glare test
  • Contrast sensitivity test
  • Potential vision test
  • Specular microscopy of the cornea in preparation for cataract surgery


The only treatment for cataract is surgery to remove it. This is done when a person cannot perform normal activities, even with glasses. For some people, changing glasses, getting stronger bifocals, or using a magnifying lens is helpful enough. Others choose to have cataract surgery.

If a cataract is not bothersome, then surgery is usually not necessary. Sometimes there is an additional eye problem that cannot be treated without first having cataract surgery.

Cataract surgery consists of removing the lens of the eye and replacing it with an artificial lens. A cataract surgeon will discuss the options with the patient, and together they will decide which type of removal and lens replacement is best.


There are 2 types of surgery that can be used to remove lenses that have a cataract.

Extracapsular surgery consists of surgically removing the lens, but leaving the back half of the capsule (the outer covering of the lens) whole. High-frequency sound waves (phacoemulsification) may be used to soften the lens to help removing it through a smaller cut.

Intracapsular surgery involves surgically removing the entire lens, including the capsule. Today this procedure is done very rarely.


People who have cataract surgery are usually fitted with an artificial lens at the same time. The artificial lens is a synthetic (manufactured) disc called an intraocular lens. It is usually placed in the lens capsule inside the eye.

Other options include contact lenses and cataract glasses.

Surgery can be done in an outpatient center or hospital. Most people do not need to stay overnight in a hospital. The patient will need a friend or family member to assist with travel and home care after outpatient surgery. Follow-up care by the surgeon is important.

Outlook (Prognosis)

For most people, cataract surgery has a low risk of complications. With implanted artificial lenses, most people no longer need corrective lenses for distance vision. Glasses are usually necessary for reading.

Possible Complications

Vision may not improve to 20/20 after cataract surgery if other eye diseases, such as macular degeneration, are present. Ophthalmologists can usually, but not always, determine this in advance.

In infants, amblyopia and decreased visual development may occur as a result of cataracts. Early diagnosis and treatment are essential.

When to Contact a Medical Professional

Call for an appointment with your health care provider if you have symptoms such as progressive worsening of vision, decreased night vision, or problems with glare.

Also call if you have a family history of congenital cataracts, or if your child has symptoms or signs suggesting a cataract.


The best prevention involves controlling diseases that increase the risk of a cataract, and avoiding exposure to factors known to promote cataract formation.

Wearing sunglasses when you are outside during the day can reduce the amount of UV light your eyes are exposed to. Some sunglasses do not filter out the harmful UV. An optician should be able to tell you which sunglasses filter out the most UV. For patients who smoke cigarettes, quitting will decrease the risk of cataracts.

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