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What are cataracts?

A cataract is defined as clouding or loss of transparency in the lens of the eye that interferes with vision. Cataracts usually develop as a result of normal aging and are most prevalent in people over 40, with half of all people in the U.S. developing cataracts by the age of 80 (Source: NEI).

The lens is formed of water and special proteins that are initially clear. Cataracts develop when proteins of the lens begin to cluster and become denser. The formation of these protein bundles makes it difficult for light to pass through the eye to the retina and creates a discolored or opaque area in the lens.

Less commonly, cataracts may occur at any age as a result of injury to the lens. In some cases, cataracts are congenital, which means they are present at birth. Cataracts may also develop as a result of diabetes or extended use of certain medications, including corticosteroids. Cataracts due to aging, disease, or drugs tend to occur in both eyes, although the degree of severity may be different in the two eyes. A cataract caused by trauma will affect only the injured eye.

Cataracts generally develop over time and may get progressively worse as you age. In most cases, you most likely will not experience any symptoms until the cataract is advanced. Symptoms include gradually increasing haziness of vision and glare or halos from lights. Cataracts are not treated until they cause visual symptoms. Fortunately, cataract surgery is highly successful in restoring clear sight.

Cataracts generally do not indicate a medical condition that needs immediate attention. However, they can be a sign of chronic serious conditions such as diabetes. Seek prompt medical care if you have symptoms of cataracts that become bothersome or are associated with other symptoms.

What are the symptoms of cataracts?

Cataracts are painless, and they produce only visual symptoms. If you have symptoms in any other part of your body along with cataracts, they are not caused by the cataracts. But they may be related to underlying diseases such as diabetes that can also play a role in the development of cataracts.

Visual symptoms associated with cataracts

Visual symptoms associated with cataracts tend to gradually increase in severity. Common symptoms of cataracts include:

  • Blurred or double vision
  • Dulling of colors
  • Frequent need for changes in eyeglass or contact lens prescription
  • Glare or halos appearing around lights
  • Hazy vision
  • Poor nighttime vision

Symptoms that might indicate a serious condition

Cataracts themselves are not a serious condition related to your overall health. However, cataract formation may be induced or accelerated by serious underlying conditions or diseases that should be promptly identified and treated. Seek prompt medical care if you have symptoms of cataracts that become bothersome or are associated with other symptoms.

What causes cataracts?

Cataracts develop when proteins in the lens, which are normally clear, begin to clump or aggregate. This process causes discoloration and loss of transparency in the lens. Eventually, the loss of transparency interferes with the passage of light rays through the lens to the retina, and vision becomes cloudy.

In most cases, cataract formation occurs as a result of aging. However, it may also be triggered by injury to the eye, eye surgery, exposure to radiation, or excess sun exposure. Cataract may also be a congenital defect.

What are the risk factors for cataracts?

A number of factors increase the risk of developing cataracts. Not all people with risk factors will get cataracts. Risk factors for cataracts include:

  • Alcoholism or heavy alcohol ingestion

  • Diabetes (chronic disease that affects your body’s ability to use sugar for energy)

  • Exposure to radiation

  • Increasing age (over 40 years)

  • Injury to the eye

  • Overexposure to ultraviolet (UV) light from sunlight

  • Prolonged use of corticosteroids

  • Smoking

Reducing your risk of cataracts

Although you cannot change the major risk factor for cataracts, which is advancing age, you can modify some of your lifestyle habits linked to cataract. You may be able to lower your risk of developing cataracts by:

  • Decreasing your alcohol consumption

  • Keeping your blood sugar levels under control if you have diabetes

  • Quitting smoking

  • Wearing sunglasses with UV protection when outside

How are cataracts treated?

Cataracts are generally not treated until they begin to affect your vision noticeably. Some minor symptoms of cataracts, including dulling of vision or small changes in visual acuity, may be improved by nonsurgical approaches such as improved lighting or changes in eyewear prescriptions.

Once your cataracts begin to interfere with your ability to drive at night, read, or watch TV, they may be removed in a surgical procedure. Your eye surgeon will completely remove the lens of your eye and replace it with a plastic lens, called an intraocular lens, which will restore the clarity of your vision. Contact your health care provider if you feel that your cataracts are impairing your vision or quality of life.

What are the potential complications of cataracts?

Cataracts affect only your eyes and are not life threatening. However, cataracts may form as a result of an underlying chronic disease, such as diabetes, that may have serious complications. You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of untreated cataracts or underlying diseases include loss of vision and blindness.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 19
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Facts about cataract. National Eye Institute.
  2. Cataracts. JAMA Patient Page.
  3. Tierney LM Jr., Saint S, Whooley MA (Eds.) Current Essentials of Medicine (4th ed.). New York: McGraw-Hill, 2011.