A cataract occurs when the lens of the eye becomes cloudy, affecting vision. It can appear in one or both eyes but does not spread from one eye to the other. There are different types of cataracts. All may require surgical treatment.

The colored portion of the eye is the iris, behind which lies the lens. In a healthy eye, the lens focuses light on the retina at the back of the eye.

In some people, a cataract forms, and the lens becomes clouded and scatters the light instead of focusing it.

A lens is primarily proteins and water. Cataracts develop due to changes in proteins and the fibers of the lens. They usually affect people over 55, but in rare cases, can develop in children.

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The lens of the eye consists of three layers. On the outside is the capsule. Just inside the capsule lies the cortex, and within the cortex is the nucleus. Some cataracts derive their name from the layer where they develop.


This is the most common type of cataract. As a person ages, cataracts can develop as a result of natural changes to the lens in the eye.

People are more likely to develop this type of cataract if they:

  • drink too much alcohol
  • smoke
  • have diabetes
  • have undergone some types of eye surgery, such as glaucoma surgery
  • take steroids


Injury to the eye can cause lens damage that results in a cataract. The cataract may form immediately or years later.


Radiation can cause cataracts. This includes medical radiation treatment for illnesses such as cancer and the radiation in ultraviolet rays from the sun.

Congenital, or pediatric

When a baby is born with a cataract, it is known as congenital. This rare cataract can develop due to problems during pregnancy or genetic conditions.

If the cataract is large enough to affect vision, quick treatment is necessary to avoid further vision problems.


A secondary cataract develops following cataract surgery when scar tissue forms in the eye, clouding vision again. Other names for this are posterior capsule opacification and after-cataract.

This is a common type of cataract, occurring in up to 2 out of 5 people who undergo cataract surgery.


A nuclear cataract clouds the center of the lens. The nucleus tends to darken with age-related changes, sometimes changing from clear to yellow or brown.


A cortical cataract clouds the layer of the lens that is next to the nucleus. This type of cataract takes the shape of a wedge or spoke on a wheel.

Posterior capsular

A posterior capsular cataract clouds the outer layer of the lens. This cataract usually develops more quickly than other types.

Cataracts cause vision problems that usually worsen slowly over time. Sometimes, the discoloration of the lens is visible.

If the cataract is nuclear, distance vision may worsen. In addition, a person who previously used reading glasses may temporarily not need them to read.

If the cataract is cortical, it will appear cloudy and take the shape of a wedge or spoke.

Reading and vision in bright light are more difficult if the cataract is posterior cortical. Lost contrast, glare, and halos are potentially present, especially at night.

Symptoms of all cataracts include:

  • blurry or hazy vision
  • less intense colors
  • harsher glare from lights, most intense at night, particularly when driving
  • difficulty seeing at night
  • change in eyeglasses prescription

If the cataract only slightly affects vision, a doctor may suggest watchful waiting. In this case, it is appropriate to monitor eyesight and symptoms on a regular schedule.

For some cases, a new eyeglasses prescription, an antiglare coating on glasses for night driving, and increasing reading light may be sufficient.

Surgery is the course of treatment when a person can no longer engage in daily activities. Cataract surgery requires removing the obscured lens and replacing it with an artificial lens.

According to the National Eye Institute, cataract surgery is almost painless and lasts for 1 hour. Before the surgery, the doctor will place numbing drops into the eye.

The doctor will then remove the cataracts. There are two different surgical methods: Manual small incision cataract surgery (MSICS) and phacoemulsification.

MSICS is when the doctor uses small tools to make a small incision into the eye to remove the lens. In phacoemulsification, they may use a high-frequency ultrasound probe to break the lens and remove it.

After removing the lens, the doctor will place an artificial lens in the eye.

Learn what to expect during cataract surgery recovery here.

Cataracts grow slowly but tend to get worse with time. A person should contact a doctor when the following symptoms appear in one or both eyes:

  • hazy or blurry vision
  • less intense colors
  • harsher glare from lights, most intense at night, particularly when driving
  • difficulty seeing at night
  • change in eyeglasses prescription

Does Medicare cover cataract surgery?

When visiting a doctor for vision problems, including cataracts, they will take a medical history, including in relation to the eyes. They may also ask for a family history of eye health.

The doctor will perform a comprehensive ophthalmic exam, including a visual acuity test using a standard eye chart. They will measure any eyeglasses prescription and the difference in vision between the eyes.

They may perform a dilated slit-lamp examination to view the lens and other structures inside the eye.

The doctor may order other tests for glaucoma, macular degeneration, or systemic diseases such as diabetes or heart disease before confirming a diagnosis of cataracts.

Cataracts are very common. By the age of 80, more than half of all Americans have had at least one cataract.

Cataract treatment can include conservative interventions such as monitoring, brighter lighting, and antiglare lenses in eyeglasses.

Commonly, treatment is surgery to remove the affected lens and replace it with an artificial lens. This surgery is very effective, and most people experience excellent results if they follow the postoperative instructions.

Changes to the proteins in the lens of the eye cause cataracts. A cloudy area forms over the lens of the eye, which can obscure vision. This can happen in one eye or both but does not spread from one eye to the other.

There are different forms of cataracts. All of them cause the same symptoms, and some may occur within different layers of the lens.

Mild cataract treatment may include monitoring during regular checkups. Surgery is the treatment for a person whose cataracts interfere with their ability to participate in daily activities.