How cataracts develop in the eye

A cataract forms when the lens of your eye becomes cloudy. The lens is normally clear, like glass, and focuses light onto the back of your eye so you can see. Over time, proteins in the lens clump together and block light from passing through. This cloudiness happens gradually in most cases — you may not notice it at first, but eventually it affects how well you see.

The lens sits behind the colored part of your eye (the iris) and the pupil. It is made mostly of water and protein arranged in a very specific way. When that arrangement breaks down, the proteins scatter light instead of letting it through clearly. The cloudiness can start in one spot and spread, or it can develop throughout the lens.

Key Takeaways

  • Age-related cataracts form because proteins in the lens naturally break down and clump together over decades, and this is the most common cause in people over 60.
  • Prolonged sun exposure without eye protection can speed up cataract formation at any age, which is why UV-blocking sunglasses matter.
  • Certain medications (especially corticosteroids taken long-term), eye injuries, and some medical conditions like diabetes can cause cataracts to develop earlier than normal.
  • Smoking and heavy alcohol use are linked to faster cataract development, and quitting can slow the process.

Age-related cataracts: the most common cause

Most cataracts in people over 60 form straightforward because the eye ages. The proteins in your lens have been there since birth, and over decades they naturally break down and stick together. This is not a disease — it is a normal part of aging, like gray hair or wrinkles. Some people develop cataracts in their 50s, others not until their 70s or 80s. The timing depends partly on your genes and partly on how much sun exposure and other risk factors your eyes have had.

Age-related cataracts usually start at the edge of the lens and move toward the center. You may notice that colors look duller, or that you need more light to read. Driving at night often becomes harder first, because glare from oncoming headlights scatters more through a cloudy lens. The cataract grows slowly — sometimes over years — so you have time to plan treatment with your eye doctor.

Sun exposure and ultraviolet light

Ultraviolet (UV) light from the sun can damage the proteins in your lens and speed up cataract formation. This is true at any age, but the damage adds up over a lifetime. People who spend a lot of time outdoors without eye protection — farmers, construction workers, or those who live in very sunny climates — tend to develop cataracts earlier than others.

Protecting your eyes from UV light can slow cataract growth. Wear sunglasses that block 99 to 100 percent of both UVA and UVB rays whenever you are outside for more than a few minutes. A wide-brimmed hat adds extra protection. If you already have a cataract, UV protection will not reverse it, but it may keep a second cataract from forming in your other eye or slow the one you have.

Medications and medical conditions that raise your risk

Certain medications and health conditions make cataracts more likely to form. Corticosteroids — drugs like prednisone or dexamethasone taken by mouth for long periods — are the most common medication link. These are used for conditions like rheumatoid arthritis, lupus, and severe asthma. If you take corticosteroids regularly, your eye doctor should check your lens during routine visits.

Diabetes is a major risk factor. High blood sugar over time can change the lens and cause a cataract to form earlier than it would otherwise. People with diabetes should have their eyes checked at least once a year, even if their vision feels fine. Other conditions linked to cataracts include thyroid disease, myotonic dystrophy, and a history of eye inflammation or uveitis.

Some eye surgeries or treatments for other eye problems can also lead to cataracts later. If you have had surgery on your eye or radiation therapy near your head, mention this to your eye doctor so they can watch for cataract formation.

Smoking and alcohol use

Smoking speeds up cataract development. People who smoke have cataracts at younger ages than non-smokers, and the cloudiness tends to be more severe. The chemicals in tobacco smoke damage the lens proteins and reduce the eye's natural antioxidants — substances that normally protect against this kind of damage. If you smoke, quitting will slow the process, even if you have already started to develop a cataract.

Heavy alcohol use is also linked to faster cataract formation. The exact reason is not fully understood, but it may involve how alcohol affects nutrition and antioxidant levels in the body. Moderate drinking does not carry the same risk, but if you drink heavily, cutting back may help protect your vision.

Eye injury and trauma

A serious blow or injury to the eye can cause a cataract to form weeks, months, or even years later. This is called a traumatic cataract. The injury damages lens fibers, and over time those damaged areas become cloudy. Even if your eye feels fine after an injury, see an eye doctor to check for damage you cannot see. If you play contact sports or work with tools or machinery, wear protective eyewear to reduce injury risk.

Some people are born with cataracts due to an infection or genetic condition during pregnancy. These are called congenital cataracts and are much less common than age-related ones. If a baby or young child has a cataract, it needs prompt treatment to prevent vision problems later.

What you can do to slow cataract formation

You cannot prevent age-related cataracts entirely, but you can slow them down. Wear UV-blocking sunglasses and a hat outdoors. If you smoke, quitting is one of the most important steps you can take for your eyes and your overall health. Keep your blood sugar controlled if you have diabetes, and take medications exactly as prescribed. Eat a diet rich in fruits and vegetables — foods high in antioxidants like vitamins C and E may help protect your lens, though the evidence is still being studied.

Have your eyes checked regularly by an eye doctor, especially if you are over 60 or have risk factors like diabetes or long-term corticosteroid use. Early detection means you and your doctor can plan treatment before the cataract affects your daily life. Many cataracts grow slowly, and you may not need surgery for years — or ever. Regular checkups help you know where you stand.

Frequently Asked Questions

Can cataracts be caused by reading or using screens too much?

No. Reading and screen use cause eye strain and fatigue, but they do not cause cataracts. Cataracts form from protein breakdown in the lens, not from how hard your eyes work. If your eyes feel tired from screens, take breaks and adjust the lighting, but this will not prevent or cause a cataract.

If my parent had cataracts, will I definitely get them too?

Not necessarily. Genes play a role in when and how fast cataracts form, so family history matters. But age, sun exposure, smoking, and other factors also make a big difference. You can reduce your risk by protecting your eyes from UV light and avoiding smoking, even if cataracts run in your family.

Does a cataract in one eye mean I will get one in the other eye?

Often yes, but not always. Many people develop cataracts in both eyes over time, but they may form at different speeds. One eye might need surgery while the other is still clear. This is why protecting both eyes from sun damage and other risk factors matters.

Can diet or supplements prevent cataracts?

Some research suggests that antioxidants like vitamins C and E, lutein, and zeaxanthin may help slow cataract formation, but the evidence is not strong enough to say supplements will prevent them. Eating plenty of fruits, vegetables, and leafy greens is good for your overall health and may help, but it cannot stop age-related cataracts from forming eventually.