A cataract is a cloudy area on the lens of the eye. Since the lens needs to be clear to function well, this opacity causes visual disturbances and, left untreated, can eventually result in blindness.^[1]

As a cataract develops, it will start to cause visual disturbances like blurred vision, poor night vision, or difficulty differentiating colors. A halo may start to form around lights, especially at night. Some people also experience double vision and light sensitivity.^[2]

Cataracts are diagnosed with an eye examination. Although the symptoms are quite helpful in diagnosing a cataract, they can also be caused by other eye conditions, such as glaucoma. An ophthalmologist will dilate the pupil with eye drops and use a slit-lamp microscope to look at the lens and into the back of the eye.^[3]

Currently, surgery is the only recommended treatment for cataracts. The surgeon will remove the cloudy lens and replace it with an artificial intraocular lens (IOL). The ophthalmologist will pick an IOL for each patient. In some cases, this procedure can even fix a refractive error that was previously corrected with corrective lenses.^[4][5]

There is some evidence to suggest that caffeine may be helpful for preventing and treating cataracts. There is no clear answer yet, but higher coffee intake has been associated with lower cataract risk.^[6][7] Vitamin supplements like vitamin E, vitamin C, and beta carotene have been studied as potential treatments for cataracts because they are antioxidants. However, the evidence does not support their use in cataract treatment yet. There is some research to suggest that the use of vitamin B supplements, especially vitamin B₁₂, could play a role in cataract prevention.^[8][8][9]

An increased intake of fruit and vegetables is associated with a slightly decreased risk of developing a cataract. A vegetarian or vegan diet may also decrease risk, although this effect might just be due to a higher vegetable intake, specifically a higher intake of legumes.^{[10][11][12][4]}

New agents are being studied in an attempt to develop a safe and effective medical treatment so that not everyone with cataracts will have to undergo surgery. Antioxidants like N-acetylcysteine and its precursors may help to reduce oxidation within the lens and prevent the formation of cataracts. Oxysterols such as lanosterol and 5-cholesten-3b,25-diol seem to stabilize proteins in the lens, and break up protein aggregates that make the lens cloudy. Uncertainty remains about the effective dosages, and the ability to reach the appropriate dosages for the lens through topical treatments like eye drops.^[13][14]

A healthy lens is a clear structure, allowing light to enter the eye. It focuses that light onto the retina, which enables clear vision. Cataracts are caused by proteins that clump together on the lens, making it cloudy. These protein aggregates get larger over time, and may also cause the lens to discolor. A cloudy and discolored lens will not filter light appropriately and therefore cause visual disturbances. The most frequent cause of this is normal aging, and most cataracts will occur in people over the age of 60. Other contributing factors include genetics, smoking, diabetes, and sun damage. A severe trauma to the eye can also cause a cataract to develop.^[15]