A cataract is a clouding of your eye's lens that develops slowly over time

Your eye's lens is normally clear, like a camera lens. A cataract happens when the proteins in that lens clump together and make it cloudy. Light cannot pass through as easily, so your vision becomes blurry or dim. The cloudiness usually starts small and grows larger over months or years. Most cataracts develop in both eyes, though one eye may cloud faster than the other.

Cataracts are not a film that grows over your eye from the outside. The cloudiness happens inside the lens itself. You cannot catch a cataract from another person, and it is not contagious. It is a change in the lens tissue that happens to most people eventually if they live long enough.

Key Takeaways

  • A cataract is a clouding inside your eye's lens that blocks light from reaching the back of your eye clearly.
  • Cataracts develop slowly over time and are painless — you may not notice them at first.
  • Age is the most common cause, but injury, certain medications, and eye diseases can also cause cataracts.
  • The only way to remove a cataract is surgery, but you do not need surgery until the cloudiness affects your daily life.
  • Regular eye exams can catch cataracts early, before they blur your vision enough to notice.

How a cataract forms and why it happens

The lens in your eye is made of water and proteins arranged in a precise way. Over time, some of those proteins break down and stick together. When enough of them clump, they scatter light instead of letting it pass straight through. This scattering is what you see as blurriness or haziness.

Age is the most common reason cataracts form. After age 60, most people have at least the start of a cataract. Before that age, cataracts are less common but can still happen. An eye injury, even one from years ago, can trigger a cataract to form. Certain medications — especially corticosteroids taken by mouth for long periods — raise your risk. Diabetes, previous eye surgery, and intense ultraviolet light exposure over many years can also cause them.

A cataract is not caused by reading in dim light, straining your eyes, or wearing the wrong glasses. Those things may tire your eyes, but they do not create cataracts.

What you might notice as a cataract develops

Early cataracts often cause no symptoms at all. You may have one and not know it until your eye doctor finds it during an exam. As the cloudiness grows, you might notice your vision becoming gradually blurrier, like looking through a frosted window. Colors may look duller or more yellow. Bright lights might seem to have a halo or glare around them, and you may find it harder to drive at night.

Some people notice they need to change their glasses prescription more often. Others find that reading or close work becomes harder even with their usual glasses. These changes happen slowly enough that you might not connect them to your eyes at first — you may think you just need new glasses.

A cataract does not hurt. If your eye is painful, red, or has sudden vision loss, that is a different problem and you should see an eye doctor right away.

The difference between a cataract and other eye problems

Cataracts are sometimes confused with other conditions that blur vision. Presbyopia is the normal stiffening of your lens with age that makes close-up reading harder — it happens to almost everyone and is why reading glasses become necessary. A cataract is different: it clouds the entire lens, not just the focusing ability.

Macular degeneration and diabetic retinopathy damage the back of your eye, not the lens. They cause different patterns of vision loss and are found with different tests. Glaucoma damages the nerve in your eye and usually has no early symptoms. Only an eye exam can tell these apart, which is why regular checkups matter.

A cataract is also not the same as a pterygium (a growth on the white of your eye) or a corneal scar. Those are visible on the surface. A cataract is inside the lens, so you cannot see it just by looking in a mirror.

When to see an eye doctor about cataracts

You should have your eyes checked regularly by an optometrist or ophthalmologist. How often depends on your age and health. Most people over 60 should have an exam every one to two years. If you have diabetes, high blood pressure, or a family history of eye disease, your doctor may recommend more frequent visits.

See an eye doctor sooner if you notice sudden blurriness, flashing lights, a shower of floaters, or eye pain. These can signal other problems that need prompt attention. If you have gradual blurriness that you think might be a cataract, schedule a routine appointment — there is no rush, but it is worth confirming.

If you already know you have a cataract, you do not need surgery just because it exists. You need surgery only when the cloudiness interferes with activities you want to do — reading, driving, watching television, or anything else that matters to you. Some people live with mild cataracts for years without surgery.

How cataracts are diagnosed

An eye doctor diagnoses a cataract using a few straightforward tests. You will read letters on a chart to check your vision. The doctor will shine a light into your eye and look through a magnifying lens called a slit lamp to see the lens up close. This lets them see exactly where the cloudiness is and how dense it has become.

Sometimes the doctor will dilate your pupils with drops so they can see the back of your eye as well. This rules out other problems that might also be causing blurred vision. The whole exam usually takes 20 to 30 minutes. It is painless and does not require any needles or injections.

What happens if you do nothing about a cataract

A cataract will not go away on its own, and no eye drops, vitamins, or medications can reverse it once it has formed. If you choose not to have surgery, the cloudiness will continue to grow slowly. Your vision will become progressively blurrier over time.

A cataract will not cause blindness in the way that glaucoma or macular degeneration can. Even a very dense cataract leaves some light perception. However, it can eventually make it unsafe or impossible to do things you need or want to do. At that point, surgery becomes the next step.

Frequently Asked Questions

Can you get a cataract in just one eye?

Yes. Cataracts usually develop in both eyes, but they often progress at different rates. One eye may become noticeably cloudy while the other is still clear or only slightly affected. If you have had an injury to one eye, a cataract may form only in that eye.

Is a cataract the same as presbyopia?

No. Presbyopia is the normal stiffening of your lens that makes focusing on close objects harder — it happens to everyone around age 40 to 50. A cataract is cloudiness in the lens itself. You can have both at the same time, but they are different problems.

Can you prevent cataracts?

You cannot prevent all cataracts, especially age-related ones. You can reduce your risk by wearing sunglasses outdoors, managing diabetes and high blood pressure, not smoking, and limiting corticosteroid use. None of these guarantees you will not develop a cataract, but they may slow the process.

Does a cataract hurt?

No. A cataract is painless. If your eye hurts, you have redness, or your vision changes suddenly, contact an eye doctor. These are signs of a different problem that needs attention.

What is the difference between a cataract and a floater?

A floater is a small shadow that drifts across your vision, usually caused by changes in the gel inside your eye. A cataract is cloudiness in the lens that makes your whole vision blurry or dim. Floaters move with your eye movement; cataracts do not.