A cataract is a clouding of your eye's lens that develops over time
A cataract is a cloudy area that forms in the lens of your eye. The lens is the clear part inside your eye that focuses light so you can see clearly. When a cataract develops, the lens becomes cloudy or opaque — like looking through frosted glass instead of clear glass. This cloudiness blocks light from reaching the back of your eye properly, which makes your vision blurry or dim.
Cataracts form slowly in most people. You might not notice any change in your vision at first. Over months or years, the clouding can become thicker and spread across more of the lens, making it harder to see. The cloudiness does not cause pain, and it does not make your eye red or irritated — you simply notice that your vision is not as sharp as it used to be.
Cataracts are very common, especially as people get older. They are one of the leading causes of vision loss in adults over 60, though they can develop at any age. The good news is that cataracts are treatable, and catching them early helps your doctor plan the best path forward.
Key Takeaways
- A cataract is a clouding of the lens inside your eye that develops gradually and makes vision blurry or dim.
- Most cataracts form because of aging, but they can also develop from injury, certain medications, or medical conditions like diabetes.
- Early cataracts may cause only minor vision changes, but they can progress to serious vision loss if left untreated.
- An eye doctor can spot a cataract during a routine eye exam and monitor how quickly it is progressing.
- Surgery to remove the cloudy lens and replace it with an artificial one is the only way to restore clear vision once a cataract forms.
How the lens normally works and what changes with a cataract
Your eye's lens is made mostly of water and protein arranged in a very precise way. This arrangement keeps the lens clear so light can pass straight through. The lens sits behind the colored part of your eye (the iris) and works like a camera lens — it bends light rays so they focus on the back of your eye, where the retina captures the image and sends it to your brain.
When a cataract forms, the proteins in the lens begin to clump together. These clumps scatter light instead of letting it pass through cleanly. The more clumps that form, the cloudier the lens becomes and the more light gets blocked. This is why cataracts make everything look dim, blurry, or hazy — your eye is still trying to focus, but the cloudy lens is in the way.
The cloudiness usually starts in one small area of the lens and spreads outward over time. Some people develop cataracts in both eyes, though one eye often becomes cloudy before the other. The speed at which a cataract grows varies from person to person — some grow slowly over many years, while others progress more quickly.
Why cataracts develop: age, injury, and other causes
Age is the most common reason cataracts form. As you get older, the proteins in your lens naturally break down and clump together. This is a normal part of aging, which is why cataracts are so common in older adults. There is no way to prevent age-related cataracts completely, though certain steps may slow their development.
Eye injury can cause a cataract to form months or even years after the injury happens. A blow to the eye, a puncture wound, or chemical exposure can damage the lens and trigger clouding. Even if your eye heals from the injury itself, the cataract may continue to develop slowly over time.
Certain medical conditions increase your risk of cataracts. Diabetes is a major one — high blood sugar can cause the lens to swell and become cloudy. Other conditions like glaucoma or a history of eye inflammation also raise your risk. Some medications, especially corticosteroids taken for long periods, can contribute to cataract formation.
Prolonged sun exposure without eye protection may speed up cataract development. Ultraviolet (UV) light from the sun can damage the lens proteins over time. Wearing sunglasses that block UV rays when you are outside is a simple way to protect your eyes.
What you might notice: early signs and symptoms
In the early stages, you might not notice any symptoms at all. A cataract can be spotted by an eye doctor during an exam before you feel any change in your vision. As the cataract grows, you may start to notice that your vision is slightly blurry or that colors look a bit duller than they used to.
As the cataract becomes larger, more noticeable symptoms develop. Your vision may become increasingly blurry, making it hard to read, drive, or recognize faces from a distance. Bright lights might seem too harsh or cause a glare that makes it uncomfortable to look at them. You might also notice that you need more light to read or do close-up work, or that your eyeglass prescription keeps changing.
Some people describe seeing a halo or ring of light around bright objects like streetlights or headlights. Others notice that their vision looks yellowed or brownish, especially if the cataract has been developing for a long time. These changes happen gradually, so you might not realize how much your vision has changed until you compare it to how you used to see.
How doctors identify a cataract
An eye doctor — either an optometrist or an ophthalmologist — can spot a cataract during a routine eye exam. The doctor will ask about your vision and any symptoms you have noticed. Then they will use special equipment to look at your lens closely.
One common test is the slit lamp exam. The doctor shines a thin beam of light into your eye while looking through a microscope. This lets them see the lens in detail and spot any cloudiness. They can also see exactly where the cataract is located and how much of the lens it covers.
The doctor may also perform a visual acuity test to measure how well you can see at different distances. This helps them understand how much the cataract is affecting your vision. If you have a cataract, the doctor will explain what they found and discuss what happens next — whether you need surgery now or whether it is safe to wait and monitor the cataract over time.
The difference between early and advanced cataracts
An early cataract is small and affects only a small part of the lens. You may have no symptoms, or your vision might be only slightly blurry. At this stage, your eye doctor will likely recommend monitoring the cataract with regular exams rather than rushing into surgery. You may be able to manage your vision with a new eyeglass prescription or by using brighter lighting when you read or do detailed work.
An advanced cataract covers a large part of the lens and causes significant vision loss. Your vision may be so blurry that you have trouble with daily activities like driving, reading, or watching television. At this point, surgery is usually the next step. The longer you wait with an advanced cataract, the more it can affect your quality of life and your ability to do the things you want to do.
In rare cases, a very advanced cataract can become hypermature, meaning the lens proteins break down further and the lens becomes very hard. This can make surgery more complicated, which is one reason doctors usually recommend surgery before a cataract reaches this stage. Your eye doctor will help you decide when the right time for surgery is based on how much the cataract is affecting your vision and your daily life.
What happens if a cataract is not treated
If you leave a cataract untreated, it will continue to grow and your vision will continue to worsen. Over time, the cloudiness can spread across the entire lens, making it very difficult to see. You might reach a point where you cannot drive safely, read comfortably, or perform your job.
In very rare cases, an untreated cataract can lead to other eye problems. If the cataract becomes very dense and hard, it can increase pressure inside the eye and cause a condition called secondary glaucoma. This is why regular eye exams are important — your doctor can catch a cataract early and help you decide on the best timing for treatment.
The good news is that cataracts do not cause permanent damage to your eye. Even if your vision has become very poor, surgery can restore it. Once the cloudy lens is removed and replaced with an artificial lens, your vision can improve significantly. There is no rush to have surgery immediately, but waiting too long can mean living with poor vision longer than necessary.
Frequently Asked Questions
Can cataracts go away on their own?
No, cataracts do not go away without treatment. Once the proteins in your lens begin to clump together, they do not separate again. The cloudiness will stay the same or get worse over time. Surgery is the only way to remove a cataract and restore clear vision.
Is a cataract the same thing as presbyopia or astigmatism?
No, they are different eye conditions. Presbyopia is difficulty focusing on close objects as you age, and astigmatism is an irregular curve in your cornea that blurs vision at all distances. A cataract is cloudiness in the lens itself. You can have a cataract and one of these other conditions at the same time.
Can you get a cataract in only one eye?
Yes, cataracts often develop in one eye first. The other eye may develop a cataract later, or it may never develop one. Even if both eyes eventually get cataracts, they usually progress at different speeds, so one eye may need surgery before the other.
Does a cataract hurt or cause redness?
No, cataracts do not cause pain, redness, or irritation. The only symptom is blurry or dim vision. If your eye is red, painful, or uncomfortable, that is a sign of a different eye problem and you should see a doctor right away.
Can wearing glasses or contacts correct a cataract?
No, glasses or contacts cannot fix a cataract because the problem is the cloudiness in the lens itself, not the shape of your eye. A new eyeglass prescription might help a little in the very early stages, but as the cataract grows, glasses will not restore clear vision. Surgery is the only treatment that works.