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Cataracts - External and Internal Eye
Other Resources UpToDate PubMed

Cataracts - External and Internal Eye

Contributors: Brandon D. Ayres MD, Christopher Rapuano MD, Harvey A. Brown MD, Sunir J. Garg MD
Other Resources UpToDate PubMed


A cataract is a change in the clarity of the natural crystalline lens. The development of a cataract is an age-related phenomenon and is more common in elderly individuals. The etiology of the color change is likely a change in water and protein content of the lens and possibly oxidative damage. There are 3 major types of cataracts, and each tends to present with different symptoms. Typically, a cataract will cause slow progressive blurring of vision; however, a nuclear sclerotic cataract (generalized clouding of the lens) can increase the refractive power of the lens inducing myopia, allowing reading vision without the use of glasses. Cortical cataracts (spoke-like opacities in the outer layers of the lens) often cause glare with oncoming light. Posterior sub-capsular cataract (web-like opacities at the posterior pole of the lens) can be highly symptomatic with blurred vision, even when very small. Cataracts can further be classified by severity, from immature (scattered opacities) to mature (totally opaque) to hypermature / Morgagnian (swollen, starting to liquify).

Though cataract formation is a naturally occurring event, several medical conditions can predispose or accelerate formation. Patients with diabetes, hypocalcemia (hypoparathyroid), myotonic dystrophy, high myopia, and inherited metabolic conditions may form cataracts earlier in life. Ocular trauma can also rapidly induce cataract formation.

Related topic: Congenital cataract


H26.9 – Unspecified cataract

193570009 – Cataract

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

The differential diagnosis for reduced vision is extensive; the more common diagnoses in an elderly population include:
Rapidly progressive loss of vision is not typical of cataract. In these patients, other reasons for visual loss should be ruled out before attributing it to cataract.

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Management Pearls

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Updated:12/05/2017
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Patient Information for Cataracts - External and Internal Eye
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Contributors: Medical staff writer


A cataract is any clouding of the human lens. This clouding can cause a reduction in vision. The lens is composed of protein and water structured to allow light to clearly pass through. Changes to the structure of the protein result in a cataract. The changes in vision associated with a cataract depend upon which part of the lens is affected.

Who’s At Risk

Normal aging of the lens results in cataracts, but the age that this occurs is variable. There are many forms of cataracts (age-related, congenital, secondary, and traumatic), so all age groups can be affected. Children can be born with cataracts, and seniors may live into their 90s and still have very little cataract change and, therefore, little effect on their vision.

Signs & Symptoms

Only when the cataract becomes dense enough can one see it with the naked eye. Since the lens is located behind the colored part of the eye (the iris), one has to look in the pupil to see if there is any change. Typically, the lens affected by the cataract will appear gray, gray/white, or yellow/tan and, rarely, the lens will be pearly white in appearance. Suspect a cataract when:
  • Vision is cloudy, blurry, or there are multiple images.
  • Glare is bothersome, such as from headlights or street lights.
  • Night vision seems reduced.
  • Changes in glasses prescriptions are needed frequently.
  • One has trouble judging distances - such as missing steps or having difficulty parking a car.
  • Color vision is altered, in that colors are faded or shades of color are difficult to discern.

Self-Care Guidelines

There are no proven ways to prevent cataracts, but there are several things you can do that may affect the development of cataracts.
  • Avoid smoking.
  • Use sunglasses with UV protection.
  • Follow a healthy lifestyle with diet and exercise.
  • Avoid long-term exposure to X-rays.
  • Avoid alcohol abuse.
  • Maintain strict control of diabetes if applicable.
  • Use of anti-oxidant vitamins may slow the development.
The side effect of some medications is the development of cataracts, such as long-term use of steroids at high enough levels. Additionally, certain general diseases, such as diabetes, are associated with cataracts.

When to Seek Medical Care

When vision is affected enough to interfere with your life and lifestyle, seek professional care. For example, if you are changing your glasses frequently due to cataracts.


The definitive treatment for cataracts is surgery. Typically, the cataractous lens is removed and an artificial lens is implanted into the eye.


Yanoff Myron, Duker JS, eds. Ophthalmology. 2nd ed, p. 275. St. Louis, MO: Mosby, 2004.
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Cataracts - External and Internal Eye
A medical illustration showing key findings of Cataracts : Blurred vision, Bilateral distribution, Diplopia, Vision loss, Opaque lens
Clinical image of Cataracts - imageId=3114289. Click to open in gallery.  caption: 'A blue-white discoloration in the pupillary space.'
A blue-white discoloration in the pupillary space.
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