What is the most common cause of blindness in the world?

Cataracts are the most common cause of blindness worldwide. A cataract is a cloudy area in the eye’s normally transparent lens, the structure that focuses light onto the retina.

Most cataracts develop gradually with aging. As lens proteins are damaged and clump together, vision may become blurry, colors may look faded, and bright lights may produce glare or halos. Cataracts can affect one or both eyes, and they are not the same as a film growing over the eye. The clouding occurs inside the lens.

Cataracts can also result from eye injury, radiation, certain medications, diabetes, or congenital conditions. In 2020, cataracts were estimated to account for about 39.6% of blindness worldwide. Their global impact is especially large where eye-care services and cataract surgery are difficult to access.

Early symptoms may sometimes be managed with updated glasses or better lighting, but surgery is the definitive treatment when vision loss interferes with daily life. The cloudy lens is removed and replaced with an artificial intraocular lens. Glaucoma and diabetic retinopathy are major causes of vision loss, but neither is the leading global cause of blindness.