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What is a cataract?

closeup of an eyeball with cataract

A cataract is a clouding of the eye’s lens, the clear, oval-shaped structure that rests behind the pupil inside every eye.

Most cataracts occur as a result of getting older, usually sometime after age 40. As we age, the proteins that help make up the lens can start to clump together, which causes the clouding. 

Cataracts are the most common cause of vision loss worldwide, but they are treatable.

SEE RELATED: What causes cataracts?

How cataracts affect your vision

Cataracts usually develop in both eyes, but sometimes they only affect one.

When both eyes are affected, cataracts can progress at a different rate in each eye, causing visual symptoms in one eye and normal vision in the other.

A cataract won’t affect your vision in the beginning. Visual symptoms can take many years to become noticeable.

Cataracts can make your vision appear blurry, cloudy, hazy or dim. Some cataracts cause colors to appear less vibrant and yellowed, like a sepia-tone photo.

Additionally, symptoms of cataracts can include:

To the outside viewer, an advanced cataract can cause the pupil to appear light gray instead of black.

SEE RELATED: More cataracts symptoms

Common types of cataracts

There are many cataract types, but a few are much more common than the others.

  • Nuclear cataracts are the most common form of cataract. These form in the center of the eye’s lens, gradually worsening and affecting vision.

  • Cortical cataracts affect the outer edges of the lens. These make you experience more light glare, making night driving particularly difficult.

  • Posterior subcapsular cataracts develop along the back of the lens. These tend to develop much more quickly than the others, specifically affecting your vision around bright light and colors.

Diagnosing and treating cataracts

Eye doctors can use different tests to diagnose cataracts. These include:

Slit-lamp exam

A doctor uses a microscope and a small, bright light to examine the front of your eye. This also allows them to partially check the lens for cataracts.

Retinal exam

First, an eye doctor will dilate your eyes with eye drops, causing the pupils to slowly open. This gives the doctor a much better view inside your eye. The doctor then examines the retina and optic nerve in the back of your eye. A dilated eye exam provides the best view of any cataract formation on the lens.

Refraction test

Also called a visual acuity test, a refraction test determines the overall sharpness and quality of your vision. An eye doctor will test each eye’s vision with a chart full of letters that appear smaller on every line.

Cataracts don’t always require treatment after they’re diagnosed, especially if they aren’t bothering you. Initially, you may be able to improve your vision with new glasses or visual aids.

If cataracts start to affect your quality of life, then your eye doctor may suggest surgery. This is generally seen as a low-risk and effective way to restore your vision.

SEE RELATED: Cataract treatment and surgery

Cataract risk factors

Certain things may affect the development of cataracts or how quickly they advance. In addition to other causes, risk factors include:

  • Excessive UV radiation

  • Diabetes

  • High blood pressure

  • Smoking

  • Obesity

  • Excessive alcohol intake

  • Long-term use of steroid or statin medications

  • Eye injury

  • Eye inflammation

  • Family history of cataracts

Stress, digital screens and mild to moderate dehydration are not known to cause cataracts.

Preventing cataracts

Nothing is guaranteed to stop cataracts from developing. Many times, they simply appear as we age.

However, if you can limit some of the risk factors listed above, it may slow the rate at which cataracts develop. Ways to limit cataract risk factors can include:

  • Wearing sunglasses during the daytime to reduce your eyes’ exposure to the sun’s UV radiation.

  • Quitting smoking.

  • Eating a healthy diet and maintaining an exercise regimen, even if it’s just light physical activity like walking.

  • Managing and reducing the effects of coexisting conditions like diabetes or hypertension.

  • Getting frequent eye exams to ensure any developing cataracts are diagnosed as early as possible.

SEE RELATED: Cataract prevention

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