Cataract

Cataract
Magnified view of a cataract seen on examination with a slit lamp
Specialty	Ophthalmology, Optometry
Symptoms	Faded colors, blurry vision, halos around light, trouble with bright lights, trouble seeing at night[1]
Complications	Falling, depression, blindness[2][3]
Usual onset	Gradual[1]
Causes	Aging, trauma, radiation exposure, following eye surgery, genetic[1][4][5]
Risk factors	Diabetes, smoking tobacco, prolonged exposure to sunlight, alcohol[1]
Diagnostic method	Eye examination[1]
Prevention	Sunglasses, proper diet, not smoking[1]
Treatment	Glasses, cataract surgery[1]
Frequency	60 million (2015)[6]

A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision of the eye.^[1][7] Cataracts often develop slowly and can affect one or both eyes.^[1] Symptoms may include faded colours, blurry or double vision, halos around light, trouble with bright lights, and difficulty seeing at night.^[1] This may result in trouble driving, reading, or recognizing faces.^[8] Poor vision caused by cataracts may also result in an increased risk of falling and depression.^[2] Cataracts cause 51% of all cases of blindness and 33% of visual impairment worldwide.^[3][9]

Cataracts are most commonly due to aging but may also occur due to trauma or radiation exposure, be present from birth, or occur following eye surgery for other problems.^[1][4] Risk factors include diabetes, longstanding use of corticosteroid medication, smoking tobacco, prolonged exposure to sunlight, and alcohol.^[1] In addition to these, poor nutrition, obesity, chronic kidney disease, and autoimmune diseases have been recognized in various studies as contributing to the development of cataracts.^[10] Cataract formation is primarily driven by oxidative stress, which damages lens proteins, leading to their aggregation and the accumulation of clumps of protein or yellow-brown pigment in the lens. This reduces the transmission of light to the retina at the back of the eye, impairing vision. Additionally, alterations in the lens’s metabolic processes, including imbalances in calcium and other ions, contribute to cataract development.^[11][1] Diagnosis is typically through an eye examination,^[1] with ophthalmoscopy and slit-lamp examination being the most effective methods. During ophthalmoscopy, the pupil is dilated, and the red reflex is examined for any opacities in the lens. Slit-lamp examination provides further details on the characteristics, location, and extent of the cataract.^[12]

Wearing sunglasses with UV protection and a wide brimmed hat, eating leafy vegetables and fruits, and avoiding smoking may reduce the risk of developing cataracts, or slow the process.^[1][13] Early on, the symptoms may be improved with glasses.^[1] If this does not help, surgery to remove the cloudy lens and replace it with an artificial lens is the only effective treatment.^[1] Cataract surgery is not readily available in many countries, and surgery is needed only if the cataracts are causing problems and generally results in an improved quality of life.^{[1][14][4][15]}

About 20 million people worldwide are blind due to cataracts.^[4] It is the cause of approximately 5% of blindness in the United States and nearly 60% of blindness in parts of Africa and South America.^[15] Blindness from cataracts occurs in about 10 to 40 per 100,000 children in the developing world, and 1 to 4 per 100,000 children in the developed world.^[7] Cataracts become more common with age.^[1] In the United States, cataracts occur in 68% of those over the age of 80 years.^[16] Additionally they are more common in women, and less common in Hispanic and Black people.^[16]