Alternate Names : Lens opacity
A cataract is a cloudy area in the lens of the eye.
This article focuses on cataracts in adults. For information on cataracts in children, see: Congenital cataracts
Overview, Causes, & Risk Factors
The lens of the eye is normally clear. If the lens becomes cloudy, the condition is known as a cataract. Rarely, cataracts may be present at or shortly after birth. These are called congenital cataracts.
Adult cataracts usually develop very gradually with advancing age and may run in families. They develop slowly and painlessly, and vision in the affected eye or eyes slowly gets worse.
Cataracts develop more quickly if there are some environmental factors, such as smoking, exposure to other toxic substances, and exposure to excessive ultraviolet light or sunlight. They may develop at any time after an eye injury. Diseases such as diabetes also greatly increase the risk for cataracts. Certain medications, such as cortisone, can also speed up cataract formation.
Adult cataracts are classified as immature, mature, and hypermature.
- Immature cataract — lens has some remaining clear areas
- Mature cataract — completely cloudy, or opaque lens, which means you can’t see through it
- Hypermature cataract — lens tissues are breaking down and leaking through the surface covering, which can damage other structures in the eye
Most people develop some mild clouding of the lens after age 60. About 50% of people ages 65-74, and about 70% of those 75 and older have cataracts that affect their vision.
Factors that may contribute to cataract development are:
- Diseases that cause inflammation or affect metabolism
- Eye injury
- Family history
- Long-term use of corticosteroids or certain other medications
- Radiation exposure
- Too much exposure to ultraviolet light (sunlight)
In many cases, the cause of cataract is unknown.
Pictures & Images
The eye is the organ of sight, a nearly spherical hollow globe filled with fluids (humors). The outer layer or tunic (sclera, or white, and cornea) is fibrous and protective. The middle tunic layer (choroid, ciliary body and the iris) is vascular. The innermost layer (the retina) is nervous or sensory. The fluids in the eye are divided by the lens into the vitreous humor (behind the lens) and the aqueous humor (in front of the lens). The lens itself is flexible and suspended by ligaments which allow it to change shape to focus light on the retina, which is composed of sensory neurons.
A slit-lamp, which is a specialized magnifying microscope, is used to examine the structures of the eye (including the cornea, iris, vitreous, and retina). The slit-lamp is used to examine, treat (with a laser), and photograph (with a camera) the eye.
Cataract – close-up of the eye
This photograph shows a cloudy white lens (cataract) over the pupil. Cataracts are a leading cause of decreased vision in older adults, but children may have congenital cataracts. With surgery, the cataract can be removed, a new lens implanted, and the person can usually return home the same day.
Cataract surgery – series
The lens of an eye is normally clear. A cataract is when the lens becomes cloudy as you get older.
Cataract : Overview, Causes, & Risk Factors
Cataract : Symptoms & Signs, Diagnosis & Tests
Cataract : Treatment
Review Date : 8/11/2009
Reviewed By : Edward B. Feinberg, MD, MPH, Professor and Chair Emeritus, Department of Ophthalmology, Boston University School of Medicine, Boston, MA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.