A cataract is the lens inside your eye turning cloudy. It isn't a growth, it isn't a film on the surface, and it isn't something you did. About two out of three people over 80 have one, and it's one of the most treatable things in all of eye care.
This page is the plain version of what a cataract is. What you'd notice, and what to do about each thing you notice, has its own page and its own video further down.
What the lens does
Behind the colored part of your eye sits a small, clear lens. It focuses light onto the retina at the back of the eye, the way a camera lens focuses light onto film, and it adjusts that focus so you can see clearly at different distances.
When you're young the lens is like a clean window. Light passes straight through. Over the years the proteins inside the lens pack together and start to cloud it, usually beginning in the center. That cloudy patch is a cataract.
What a cataract does to your vision
Think of looking through a window that hasn't been cleaned in years. Nothing is wrong with the view. The window is in the way. A cataract does that to your vision: things look blurry, hazy or less colorful, and the cloudier the lens gets, the more of the picture it takes with it.
It doesn't hurt, and it doesn't happen overnight. It builds over years, often in both eyes at close to the same pace, which is why so many people don't notice how much has changed until something forces the comparison.
What you'd notice
A page about what a cataract is can't tell you what yours is doing to your day. The video below can. It's the six changes people notice before anyone says the word cataract, where each one shows up in an ordinary week, and something to try for each one.
In it: why your prescription keeps changing and then new glasses stop helping, why night driving gets worse before anything else does, and the one change that happens so slowly you can't see it yourself. The written version, with the things that never made it on camera, is here: Cataract symptoms: the 6 things you notice first.
What to do about it
The symptoms of a cataract overlap with other eye problems, so the first step is an eye exam that looks at the whole eye, not a recheck of your glasses numbers. If the exam finds a cataract that's getting in the way of your day, the treatment is cataract surgery: the cloudy lens comes out and a clear artificial lens goes in. That's a decision you make at your own pace. Cataracts have stages, and the stages page explains what the words your eye doctor uses mean.
Common questions
How long does it take to go blind from cataracts?
In a country with access to eye care, it almost never happens. A cataract progresses slowly, usually over years, and at any point along the way it can be removed and vision can usually be improved. Untreated for a very long time, a cataract can take vision down to light and shadows. Even then surgery can usually improve it, though other eye conditions can limit how much comes back.
What are the early signs of cataracts?
Glasses prescriptions that change faster than they used to, new glasses that don't help, more glare and halos around lights at night, needing more light to read, and colors that look faded or yellowed. They arrive slowly, one at a time, and each one is easy to blame on something else.
Can cataracts be prevented?
Not entirely. An age-related cataract is part of the lens getting older, and no drop, diet or supplement has been shown to reverse one. What slows it down is taking the accelerators off the table: not smoking, wearing sunglasses that block UV, keeping blood sugar controlled if you have diabetes, and regular eye exams so it's found early.
Do cataracts cause complete blindness?
Not when they're treated. A cataract left alone for many years can reduce vision to light and shadow, but the lens can be replaced at almost any stage and vision can usually be improved. Cataract is still the leading cause of blindness in the world, about half of it, and in nearly all of those cases the missing piece is access to surgery, not the cataract itself.
How do you fix eye cataracts?
Cataract surgery. The cloudy lens is broken up and removed through a very small opening, and a clear artificial lens, called an intraocular lens or IOL, is placed where the old one was. It's an outpatient operation, done one eye at a time, and the lens is meant to last the rest of your life.
Can cataracts be treated without surgery?
Early on, yes, in the sense that better lighting, an updated glasses prescription and anti-glare coatings can keep you comfortable for a while. None of those treat the cataract. They work around it. When the workarounds stop being enough, surgery is the only treatment that removes it.
Reviewed by Hussain Elhalis, MD · September 16, 2026