Cataract

A cataract is a cloudy patch that forms in the eye's lens, leading to vision problems. The speed at which it progresses varies by type, and it can affect either one or both eyes.

Signs and symptoms

Common symptoms include colors that seem faded, blurry or double vision, seeing halos around lights, sensitivity to bright light, and trouble seeing at night. These issues can make driving difficult, reduce independence, and interfere with daily tasks. Poor vision from cataracts also raises the risk of falls and depression.

Causes

While aging is the most frequent cause, cataracts can also result from eye injuries, radiation exposure, conditions present at birth, or complications from other health problems. Risk factors include diabetes, long-term use of corticosteroid medications, obesity, other eye diseases, poor diet, smoking, prolonged sun exposure, and alcohol consumption. The clouding happens mainly due to oxidative stress and aging, as the eye's natural lens-clearing systems break down over time.

Diagnosis

Diagnosis involves an eye exam that tests vision at different distances, uses a slit lamp to examine the lens in detail, and checks the retina with an ophthalmoscope or special lenses. The eye may be dilated for a better view of the retina. Cataracts are classified by where the clouding occurs: nuclear (center of the lens), cortical (outer part), and posterior subcapsular (back of the lens) are the three most common types.

Prevention

As of 2025, no proven method exists to prevent or delay age-related cataracts, though risk factors like alcohol, smoking, and UV exposure can be managed. In early stages, glasses may improve symptoms. If that doesn't help, the only effective treatment is surgery to remove the cloudy lens and replace it with an artificial one. This surgery is not widely available in many countries and is only needed when cataracts cause problems; it generally improves quality of life.

As of 2020, about 12 to 15 million people worldwide are blind from cataracts, and over 200 million have some visual impairment due to the condition. Cataracts are the single most common cause of blindness.

Across all ages, the prevalence is 17.2%, with nuclear and cortical cataracts being the most frequent types. They become more common with age and are more common in women. Most people with cataracts live in lower-income countries, with South Asia having the highest rates of cataract-induced blindness.