A cataract is a clouding of the natural lens inside your eye. The lens sits just behind the colored part of your eye (the iris) and is normally clear, bending light so it focuses sharply on the retina at the back. When proteins in the lens clump together and lose their transparency, the result is a hazy, frosted-glass effect that scatters light instead of transmitting it cleanly. Cataracts are the leading cause of blindness worldwide and affect roughly half of all people over age 65.
What Happens Inside the Lens
Your eye’s lens is made almost entirely of water and specialized proteins called crystallins. These proteins are arranged in a precise, orderly pattern that keeps the lens transparent. For the lens to stay clear, every crystallin molecule needs to hold its correct three-dimensional shape for your entire life, because the lens has no blood supply and cannot replace damaged proteins the way most tissues can.
Over time, cumulative damage from UV radiation, oxidation, and other chemical changes destabilizes those protein structures. The proteins partially unfold, become sticky, and clump into large, insoluble clusters. These clusters scatter incoming light rather than letting it pass through, which is what produces the characteristic cloudiness of a cataract. The process is slow, often unfolding over years or decades, which is why most cataracts appear gradually in middle age or later.
Types of Cataracts
Not all cataracts form in the same part of the lens, and where the clouding develops determines which visual symptoms you notice first.
Nuclear Sclerotic Cataract
This is the most common age-related type. It forms in the central core (nucleus) of the lens, which slowly yellows and hardens over years. One of its signature quirks is called “second sight”: as the hardening nucleus changes the lens’s focusing power, some people who previously needed reading glasses find they can suddenly read without them. That improvement is temporary. As the yellowing deepens, distance vision blurs, colors appear faded or washed out, and night driving becomes difficult because of glare and poor contrast. The color shift from clear to yellow to brown happens so gradually that many people don’t realize how much color perception they’ve lost until after the cataract is removed.
Cortical Cataract
Cortical cataracts develop in the outer ring of lens fibers that surrounds the nucleus. They typically start as white, wedge-shaped streaks on the periphery of the lens and grow inward. How much they affect your vision depends on how close the opacities get to the center of the lens. The hallmark complaint is glare, particularly from oncoming headlights at night. Contrast sensitivity also drops, making it harder to distinguish objects against similarly colored backgrounds.
Posterior Subcapsular Cataract
This type forms on the back surface of the lens, right in the path where light converges before hitting the retina. Because of that location, even a small opacity can cause noticeable problems. It tends to interfere with both near and distance vision and creates significant difficulty in bright lighting conditions. Posterior subcapsular cataracts often progress faster than the other types and are more common in younger adults, people who use corticosteroid medications long term, and those with diabetes.
Symptoms to Recognize
Early cataracts often produce no symptoms at all. As the clouding progresses, common signs include:
- Blurred, dim, or cloudy vision
- Needing brighter light for reading
- Halos or starbursts around lights at night
- Increasing difficulty with night driving
- Fading or yellowing of colors
- Frequent changes in your glasses or contact lens prescription
- Double vision in one eye
Because the changes are gradual, many people unconsciously compensate, turning on more lights or holding reading material closer, without recognizing that a cataract is the underlying cause.
What Causes Cataracts Beyond Aging
Age is by far the biggest risk factor, but cataracts can also develop earlier in life for other reasons. Diabetes accelerates protein damage in the lens, making cataracts more likely at a younger age. Long-term use of corticosteroid medications, whether oral, inhaled, or in eye drop form, increases risk for the posterior subcapsular type specifically. Blunt or penetrating eye injuries can disrupt the lens fibers and cause a traumatic cataract, sometimes within weeks of the injury. UV exposure, smoking, and heavy alcohol use all contribute to the cumulative protein damage that drives cataract formation. Some cataracts are congenital, present at birth or developing in early childhood due to genetic conditions or infections during pregnancy.
Who Gets Cataracts
Cataracts are extraordinarily common. A 2025 analysis published in Frontiers in Medicine found that the global prevalence among adults 60 and older was roughly 7,749 per 100,000 people in 2021. The burden is not evenly distributed: South Asia had the highest rates (about 17,757 per 100,000), followed by Oceania and parts of Sub-Saharan Africa, while high-income regions like Japan, Australia, and Western Europe had rates three to five times lower. Countries with fewer resources for eye care carry a disproportionate share of cataract-related blindness. Projections suggest the total number of cataract cases worldwide could reach 160 to 211 million by 2050 as populations age.
How Cataracts Are Diagnosed
An eye care professional can detect cataracts during a routine dilated eye exam. After dilating your pupils with drops, they use a slit lamp, a microscope with a thin beam of bright light, to examine the lens layer by layer. This allows them to see exactly where the clouding is located, how dense it is, and which type of cataract you have. A standard vision chart test measures how much the cataract is affecting your sharpness of sight. In many cases, cataracts are found during exams scheduled for other reasons, like updating a glasses prescription, before you’ve noticed any symptoms yourself.
When and How Cataracts Are Treated
In the early stages, a stronger glasses prescription, better lighting, or anti-glare sunglasses may be enough to manage symptoms. There is currently no medication, eye drop, or supplement proven to reverse or prevent cataracts once they start forming.
Surgery becomes the recommended option when the cataract interferes with daily life. There is no fixed vision score that automatically triggers the decision. Instead, the key questions are practical: Can you drive safely? Can you read, cook, manage stairs, and take medications without difficulty? Do bright lights make it significantly harder to see? If the cataract is limiting your independence or your ability to do the things that matter to you, surgery is typically the next step. Cataracts may also need to be removed if they block your eye doctor’s ability to examine or treat other conditions at the back of the eye, such as diabetic retinal disease.
Cataract surgery is one of the most frequently performed procedures in the world. The clouded natural lens is broken up and removed through a tiny incision, then replaced with a clear artificial lens. The procedure is done on an outpatient basis, usually takes under 30 minutes, and most people notice sharper vision within a few days. Recovery is generally straightforward, with full healing over four to six weeks.