A cataract is a clouding of the eye's lens. It makes it hard for you to see. A cataract won't spread from one eye to the other, but many people get them in both eyes.

Normal Anatomy of the Eye

Copyright © Nucleus Medical Media, Inc.

As the cataract grows and gets cloudier, it may become harder to read and do other tasks. Many people are not aware that their eyesight is blurry because cataracts grow slowly over time.


Copyright © Nucleus Medical Media, Inc.

The cause of this clouding is not known. Many things can lead to cataracts forming, such as:

  • Aging
  • Smoking
  • Drinking too much alcohol
  • Health problems, such as diabetes
  • Some infections
  • Eye disease, or injury or burns of the eye
  • Exposure to radiation, toxins, or some medicines
  • Taking steroid medicines for a long time
  • Too much time spent in the sun
  • Problems found at birth

Cataract. American Optometric Association website. Available at: https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/cataract?sso=y. Accessed February 13, 2019.

Cataracts in adults. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T116240/Cataracts-in-adults. Updated November 28, 2016. Accessed May 10, 2017.

Facts about cataract. National Eye Institute website. Available at: https://nei.nih.gov/health/cataract/cataract_facts. Updated September 2015. Accessed February 13, 2019.

Informed consent: obtaining from patients undergoing surgery. EBSCO Nursing Reference Center website. Available at:http://www.ebscohost.com/nursing/products/nursing-reference-center. Updated September 14, 2018. Accessed February 13, 2019.

What are cataracts? American Academy of Ophthalmology website. Available at: https://www.aao.org/eye-health/diseases/what-are-cataracts. Updated November 9, 2018. Accessed February 13, 2019.

What is a cataract? NIH Senior Health website. Available at: https://nihseniorhealth.gov/cataract/whatisacataract/01.html. Updated January 2013. Accessed May 10, 2017.

Last reviewed December 2018 by EBSCO Medical Review Board James P. Cornell, MD  Last Updated: 2/14/2019