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What Is a Cataract? Everything You Need to Know

There are three main types of cataracts, and their names are named based on where they develop on the eye lens. Early symptoms may glare with night driving or with bright light. Cataracts do not cause pain. progression is usually gradual. However, nothing can reverse a cataract once it has begun to develop; there is no way to get the lens to go back to “normal.”

Cataracts are diagnosed through a comprehensive eye examination. Treatments vary based on the level of vision impairment.

The definitive treatment for a cataract, once it has become bad enough, is to remove it through surgery. This operation is very common and, in the vast majority of cases, very successful. Some measures to prevent a cataract can be helpful if begun long enough before a cataract has started to develop.

What Are Cataracts?

Light passes through the lens of your eye, which focuses and bends the light, to help your brain process the images you see. A normal lens is clear.

It is projected that by 2050 approximately 50 million Americans will have cataracts.

National Eye Institute

Cataracts cause a clouding of the lens that can make vision foggy. Your eye can no longer focus light to make a clear image. The changes in your vision are dependent on the severity and location of the cataract.

A cataract forms as the proteins in your lens start to break down as you age. They may then clump together or become darker, which can make it more difficult for light to travel through normally. Sometimes little pockets of fluid can build up in the lens, making it more difficult for the light to pass through

Cataracts generally develop slowly over time. They are very commonly a result of aging and changes in the eye that happen after the age of 40, the American Academy of Ophthalmology (AAO) explains.

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Types of Cataracts

The lens of the eye is composed of several layers. A cataract can form in any of the layers. The outside layer of the lens is the capsule; it is like a sac that contains the lens and is almost always clear; the next layer is the cortex; finally, the middle of the lens is the nucleus. If you think of a cherry, the pit is the nucleus, the pulp is the cortex and the skin is the capsule.

These are types of cataracts:

  • Posterior sub-capsular cataract: In this type of cataract, the cloudiness develops on the inside of the back part of the capsule. It is the type that can progress the most rapidly; even a small amount of cloudiness in this area can significantly decrease the vision.
  • Nuclear cataract: Often called nuclear sclerosis; in his type the nucleus darkens with age, often turning yellow or even brown. Nuclear cataract usually has the most impact on color perception which you may not notice until the cataract is removed.
  • Cortical cataract: This type forms in the cortex. Usually there are white wedges or spokes (arranged like the spokes of a bicycle wheel) around or in front of the nucleus.

How Do Cataracts Form?

The lens of your eye is comprised mostly of water and proteins. Normally, these proteins are arranged in a way that makes the lens clear and allows light to pass through it without interference.

Certain things can cause the proteins to clump together, disrupting their normally orderly arrangement. This disorganization can interfere with the normal passage of light rays . As the changes progress, the proteins themselves can deteriorate which further adds to the disorganization.

What Causes Cataracts?

Cataracts are a common side effect of aging.

National Eye Institute

Cataract development is mostly associated with aging; they are very common. In fact, live long enough, and you will get cataracts. Although it’s not really an answer, what causes cataracts, for the most part, are the same things that cause gray hair. Fortunately, most cataracts develop quite slowly so it may take years before intervention is necessary.

Although much less common, there are other causes of cataract besides aging. Cataracts can also form as the result of injury or trauma to the eye, use of certain medications especially steroids, environmental factors such as exposure to radiation, certain metabolic conditions, or they may be present from birth (congenital).

How Common Are They?

Cataracts are extremely common. More than half of American adults ages 80 or older either have cataracts or have had surgery to treat cataracts.

By 2050, it is projected that approximately 50 million Americans will have cataracts.


As cataracts develop slowly, changes to your eyesight can also be gradual. Some of the common symptoms of a cataract include the following:

  • Blurry or hazy vision
  • Colors appearing muted, faded, or dulled
  • Difficulties seeing well at night, especially with driving
  • Glares or halos around lights
  • Light sensitivity, especially in bright sunlight
  • Vision prescription that changes often

These symptoms can be caused by other conditions beside cataracts, so if you experience them, you should check with your eye doctor.

Getting a Diagnosis

To diagnose cataracts, an eye doctor will perform an eye exam. Usually toward the beginning of the exam, they will perform a visual acuity and refraction test to determine the clarity of your vision and prescription (refractive error) if present.

older woman getting eye exam

Later in the exam, they will put special eye drops in your eye to widen (dilate) the pupil. This allows the doctor to be able to see almost the entire lens, among other things, with the slit-lamp microscope.

Usually, while your pupil is dilated, the doctor will examine the retina and other structures located behind the lens.

Risk Factors

In addition to aging, there are some other potential risk factors that can contribute to a faster progression of cataracts. These include the following:

  • Eye injury
  • Diabetes
  • Too much exposure to direct sunlight (UV radiation) without sunglasses
  • Smoking
  • Drinking alcohol excessively
  • Long-term use of steroids
  • Radiation treatment or occupational exposure
  • Internal eye (intraocular) surgery, such as for glaucoma or retinal problems

If you have a family history of cataracts, this can put you at more risk for developing them. There is likely a genetic component to cataracts.

Treating Cataracts

Early on, certain cataracts will mostly just create a need for a prescription for new glasses or contact lenses. Depending on other symptoms that may develop, certain lifestyle changes may be helpful:

  • Wearing anti-glare sunglasses.
  • Using stronger glasses for reading.
  • Increasing the amount of light when working at near or reading.
  • Increasing the contrast on your video or device screens.

The decision of when to remove a cataract is one you will need to make with the help of your eye doctor. In general, it doesn’t make sense to remove a cataract until it gets to the point where you will be able to tell an improvement after the surgery. However, as techniques and technology have improved, the threshold for removing a cataract has dropped lower and lower so that now, removing even a minimal cataract can yield noticeable improvements.

Cataract Surgery

Cataract surgery is one of the most common and successful surgeries performed today. It is the only method to definitively treat a cataract.

Cataract surgery involves removing the lens of the eye completely except for the capsule, the usually clear membrane surrounding the lens, and replacing it with an artificial one, an intraocular lens (IOL).

Most cataracts are removed using a technique called phacoemulsification in which a hollow vibrating needle is used to break up and vacuum out the hard (nuclear) parts of the cataract. A non-vibrating needle is then used to remove the softer parts (cortex). The capsule is left in the eye because it will be used to support the IOL. All of this is done through a small incision, usually less than 2.5mm (1/10 inch).

In recent years, a laser has been developed to do mostly the incisional parts of the surgery to a very precise degree. The laser can also break up the nucleus to make it easier to remove. The laser has other advantages related to stabilizing and positioning of the IOL. If the cataract is more progressed and denser, a larger incision may be necessary to remove the lens nucleus in one piece through extracapsular cataract surgery.

The majority of people who have cataract surgery report seeing better after the cataract is removed. Depending on the type of IOL implanted, glasses of any sort may be almost completely unnecessary.

Secondary Cataract – also known as after cataract Once removed, a cataract cannot come back. However, the back part of the capsule (posterior capsule) can become cloudy over time and, very often the symptoms are much similar to those of the original cataract. However, this is easily remedied with a non-invasive Yag laser treatment (posterior capsulotomy).


While you cannot completely prevent a cataract, or reverse changes that have already occurred, you can slow its progression and help to lower the risk of them forming by doing the following (the earlier in life you adopt these practices, the better, so maybe share this with your kids):

  • Protect your eyes from direct sunlight by wearing UV sunglasses and a hat with a brim when out in the sun.
  • Quit smoking, or better, do not start in the first place.
  • Regulate the amount and type of alcohol you drink.
  • Adopt a healthy, anti-oxidant diet, including leafy green vegetables such as spinach, collard greens, and kale.
  • Get regular comprehensive eye exams that include a dilated eye exam. If you are 60 or older, you need a dilated exam at least once every two years.

Protect your eyes from injury by wearing protective eyewear when necessary.


  1. Cataracts. (April 2020). Cleveland Clinic.

  2. What Are Cataracts? (September 2021). American Academy of Ophthalmology.

  3. Cataract. American Optometric Association (AOA).

  4. Types of Cataract. (August 2019). National Eye Institute (NEI).

  5. Causes of Cataract. (May 2019). National Eye Institute (NEI).

  6. Cataract Data and Statistics. (July 2019). National Eye Institute (NEI).

  7. Cataract. (December 2021). U.S. National Library of Medicine (NLM).

Last Updated March 22, 2022

Note: This page should not serve as a substitute for professional medical advice from a doctor or specialist. Please review our about page for more information.

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