What Are Cataracts? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Cataracts are a clouding of the lens of your eye, resulting in changes to your vision. A cataract can develop in one eye at a time or both eyes simultaneously.

The lens of your eye consists of normally clear tissue that focuses light onto your retina, the layer of nerve cells lining the back wall of the inside of the eye. In your retina, light is converted to nerve signals that communicate information to your brain. (1,2)

While cataracts are considered a disorder and often benefit from treatment, they’re also a common and even normal part of aging. By age 80, more than one-half of all people in the United States will develop at least one cataract, according to the National Eye Institute. (2)

While most cataracts are related to aging, there are also certain types that can develop during childhood or due to surgery, trauma, use of certain drugs, or other health problems.

Cataracts tend to grow progressively worse, causing vision impairment that may interfere with your daily activities. It’s important to talk to your doctor about any changes in your vision, and what options may be available for treating them. (2)

The most common initial symptom of a cataract is a small area of blurred vision. Over time, this area of blurred vision is likely to grow as your lens becomes more clouded. Eventually, you may get the sense that your overall vision is dull or blurry.

Along with vision that gets progressively blurrier, you may also experience color changes in your lens that cause everything you look at to take on a yellowish or brownish cast.

Eventually you may have trouble distinguishing colors, particularly shades of blue and purple, as well as performing tasks that require distinguishing colors, including reading.

Other than cloudy vision and color changes, symptoms of cataracts may include:

• Poor night vision
• Sensitivity to lamps, headlights, or sunlight
• Halos around lights
• Double vision
• Frequent changes to your glasses or contacts prescription (2,3)

It’s a good idea to schedule an eye exam if you notice any changes in your vision over time. If you suddenly develop a change in your vision, see an eye doctor right away.

Learn More About Signs and Symptoms of Cataracts

Cataracts are usually diagnosed by an eye doctor — an optometrist or ophthalmologist — using a variety of eye and vision tests.

You may need a dilated eye exam, in which drops are placed in your eyes to make your pupils widen so the doctor can see into the interiors of your eyes more easily. (2)

Tests that may help your eye doctor diagnose cataracts include:

Visual acuity test In this common test, you’re asked to read a series of letters from a chart.

Slit lamp exam In the basic version of this test, an eye doctor uses a special microscope to view structures in the front of your eye in detail.

Retinal exam For this test your eyes must be dilated, and your eye doctor uses a slit lamp or another device to view the backs of your eyes. (3)

Learn More About Diagnosing Cataracts: Tests and Screenings, Early Diagnosis, and Your Doctors

Prognosis of Cataracts

Age-related cataracts tend to develop slowly, sometimes taking years for noticeable vision changes to occur. There’s no way for doctors to predict how quickly your cataracts will develop or progress.

There are steps you can take that may slow the progression of your cataracts, including wearing glasses or sunglasses that block the sun’s ultraviolet (UV) rays. (1)

Cataracts don’t get better or go away on their own. While many people are able to take steps to adapt to living with cataracts, the only treatment that actually improves your vision is surgery. (2)

Cataracts don’t go away on their own. Once they develop, the vision changes they cause will be permanent unless you get surgery to correct them. (2)

Most people develop cataracts that are age-related, caused by eye changes that start around age 40. But it may take many years for this process to cause noticeable changes to your vision.

By age 60, most people have some clouding in the lenses of their eyes. But vision problems may not occur because of this clouding until years later. (1)

The decision to have surgery for cataracts is usually based on how much your symptoms affect your daily activities and quality of life. How long it takes for cataracts to develop to this point varies widely between individuals. (3)

Types of Cataracts, Based on Cause and Location

Cataracts can be broadly divided into four groups according to their causes:

• Age-related cataracts This group accounts for the large majority of cataracts.
• Congenital cataracts Cataracts in babies and children can be caused by a number of different factors.
• Secondary cataracts In adults, cataracts can be caused by diseases like diabetes, or by drugs such as corticosteroids.
• Traumatic cataracts An injury to one or both eyes may result in cataracts. This can happen soon after the injury or several years later. (4)

Cataracts can also be categorized by the area of the lens they affect. There are three types of cataract locations:

• Nuclear cataracts This type of cataract affects the center of your lens. It tends to cause yellowing and clouding of the area.
• Cortical cataracts This type of cataract affects the edges of your lens. It tends to cause white marks and streaks that gradually extend to the center of your lens.
• Posterior subcapsular cataracts This type of cataract affects the back of your lens. It tends to cause an initially small opaque area in the path of your vision, and often progresses faster than other types of cataracts. (3)

Worldwide, cataracts are the leading cause of blindness, accounting for 42 percent of all cases, according to Johns Hopkins Medicine. (5)

In some people who have surgery for cataracts — which replaces the eye’s natural lens with an artificial lens — natural lens cells grow back over time, which can lead to new cataracts (known as secondary cataracts). In fact, as many as 50 percent of people who undergo cataract surgery have natural lens cells behind their artificial lens 5 to 10 years later, according to the National Eye Institute.

Secondary cataracts may be treated by laser eye surgery, but this surgery may damage the artificial lens. (6)

Congenital cataracts — which are present at birth or develop during childhood — are the most common cause of lifelong vision loss in children. Even with early surgery and other treatments, many children with congenital cataracts end up with vision problems such as deprivation amblyopia, nystagmus, strabismus, or glaucoma. (7)

Cataracts are not known to result from, or contribute to, other types of eye disease. But many of the risk factors for cataracts — such as older age, smoking, and exposure to ultraviolet (UV) light — can also lead to other forms of eye disease or vision loss.

Common eye disorders that may overlap with cataracts include the following:

Age-related macular degeneration (AMD) This eye disorder affects the macula, the central part of the retina. When the macula thins, it can cause a gradual blurring of central vision, which can interfere with tasks like reading and driving.

Diabetic retinopathy In people with diabetes, elevated blood glucose can damage the blood vessels in the eye’s retina, causing vision loss over time. This process tends to affect both eyes, and may be slowed or reversed through good diabetes control.

Glaucoma This group of disorders is typically defined by increased pressure inside the eye, which can eventually damage the optic nerve and lead to vision loss. Early treatment of glaucoma may help prevent vision loss and blindness. (10)

American Academy of Ophthalmology

See what a cataract looks like, what looking through a cataract is like, and much more on the website of the American Academy of Ophthalmology.

American Optometric Association

Learn more about cataracts and other common eye conditions on the website of the American Optometric Association.

National Eye Institute

Get the latest updates on cataract research supported by the National Eye Institute.

National Institute on Aging

Learn how aging can affect your eyes and vision, when to see a doctor, and how to live better with low vision.