What causes cataracts, and can you prevent them? Mostly ageing, and not really
By age 80 most people have a cataract or have had one removed. You can lower some risks, but the antioxidant vitamins tested in a 4,629-person trial did not slow them, and surgery is the only cure.
A cataract is a cloudy area in the lens of the eye — the clear part that focuses light — and it is one of the most predictable consequences of getting older. The two questions people ask are what causes it and whether it can be prevented. The honest answers are: mostly ageing, and only partly.
What a cataract is and why it forms
The lens starts out clear. Around age 40, in the National Eye Institute's account, the proteins in the lens begin to break down and clump together, and that clump is what clouds the lens [s1]. At first there may be no symptoms; over time, cataracts can make vision blurry, hazy or less colourful, with trouble reading or seeing at night, halos around lights, and a need to change glasses prescriptions often [s1].
They are extraordinarily common. More than half of all Americans aged 80 or older either have cataracts or have had surgery to remove them, according to the NEI [s1]. MedlinePlus puts the age curve plainly: mild clouding often begins after age 60, and by age 75 most people have cataracts that affect their vision [s3].
The causes you can and can't change
Most cataracts are simply age-related, caused by the normal changes described above [s1]. But the NEI lists several factors that raise the risk beyond ageing alone: diabetes, smoking, drinking too much alcohol, a family history of cataracts, a previous eye injury, eye surgery or radiation treatment to the upper body, spending a lot of time in the sun, and taking steroid medicines used for conditions such as arthritis or allergies [s1]. A cataract can also follow an eye injury or surgery for another eye problem such as glaucoma [s1].
Some of those are fixed — age, family history, a past injury. Others are modifiable, and that is where prevention advice concentrates.
What actually lowers the risk
The NEI's prevention steps are concrete and unglamorous: protect the eyes from the sun with sunglasses and a brimmed hat; wear protective eyewear during activities such as using power tools or playing sports; quit smoking; and make eye-healthy food choices, eating plenty of fruit and vegetables, leafy greens, nuts and whole grains [s1]. MedlinePlus frames the same idea slightly differently, saying the best prevention involves controlling the diseases that increase risk and avoiding exposures that promote cataract formation — again, quitting smoking and wearing sunglasses to block ultraviolet rays [s3].
Notice what is missing from both lists: a supplement or a food that reliably stops cataracts from forming. That absence is not an oversight.
Why antioxidant vitamins aren't on the list
The strongest test of whether supplements slow cataracts came from the Age-Related Eye Disease Study. Its report no. 9 was a double-masked trial at 11 centres. Of 4,757 participants enrolled, 4,629 aged 55 to 80 had at least one natural lens and were followed for an average of 6.3 years [s2]. Participants were randomly assigned to a daily high-dose antioxidant tablet — vitamin C 500 mg, vitamin E 400 IU and beta carotene 15 mg — or to no antioxidants [s2].
The result was flatly negative. No statistically significant effect of the antioxidant formulation was seen on the development or progression of age-related lens opacities, with an odds ratio of 0.97 (P=0.55) [s2]. There was also no significant effect on any of the three lens-opacity types, on the need for cataract surgery, or on at least moderate visual-acuity loss [s2]. The authors' conclusion was that a high-dose formulation of vitamins C and E and beta carotene, in a relatively well-nourished older cohort, had no apparent effect on the 7-year risk of developing or progressing cataract or on visual-acuity loss [s2]. High-dose antioxidant vitamins, in other words, are not a cataract-prevention strategy, whatever their marketing.
The one thing that reliably fixes a cataract
Because no drop, diet or supplement clears a clouded lens, treatment is mechanical. Surgery is the only way to get rid of a cataract, the NEI states, though it is not always needed right away [s1]. When a cataract does interfere with everyday life, cataract surgery — one of the most common operations in the United States — is safe and corrects the vision problems it causes [s1].
This article is informational and is not medical advice. Cataracts are detected during a dilated eye exam, which the NEI suggests every one to two years from age 60 [s1]; new problems with night vision, glare or general vision loss are worth an appointment rather than a new pair of over-the-counter glasses [s3].
Sources
- Cataracts — National Eye Institute, 2026-08-19
- A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E and Beta Carotene for Age-Related Cataract and Vision Loss: AREDS report no. 9 — Archives of Ophthalmology, 2001-10-01
- Cataract (MedlinePlus Medical Encyclopedia) — U.S. National Library of Medicine (MedlinePlus), 2025-07-24
Sources
- Cataracts — National Eye Institute , August 19, 2026
- A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E and Beta Carotene for Age-Related Cataract and Vision Loss: AREDS report no. 9 — Archives of Ophthalmology , October 1, 2001
- Cataract (MedlinePlus Medical Encyclopedia) — U.S. National Library of Medicine (MedlinePlus) , July 24, 2025
Most eye floaters are harmless. Sudden floaters with flashes are a same-day problem.
Floaters are usually ageing changes in the eye's gel. But among people who suddenly develop floaters and flashes, about 14% turn out to have a retinal tear — which can lead to permanent vision loss if left.
What are the early signs of glaucoma? For the common type, there usually aren't any
Open-angle glaucoma steals side vision so slowly that half of people who have it don't know. There is no way to prevent it — but a placebo-controlled trial showed pressure-lowering drops preserve vision.
Do eye exercises improve your vision? For most claims, the evidence isn't there
Eye exercises won't sharpen blurry sight or cure nearsightedness — glasses and surgery do that. But one focusing problem, convergence insufficiency, does respond: an office-based programme helped 73% in a trial.
AREDS supplements slow advanced macular degeneration. They do not prevent AMD.
The trials that made eye vitamins a standard recommendation enrolled only people who already had substantial disease. In AREDS2, neither omega-3 nor lutein beat placebo on the primary endpoint.