Cataracts - Clouding of the Lens

What is a cataract?

A cataract is a cloud­ing of the lens in the eye that affects vision. Most cataracts are relat­ed to aging. Cataracts are very com­mon in old­er peo­ple. By age 80, more than half of all Amer­i­cans either have a cataract or have had cataract surgery.

A cataract can occur in either or both eyes. It can­not spread from one eye to the other.

What is the lens?

The lens is a clear part of the eye that helps to focus light, or an image, on the reti­na. The reti­na is the light-sen­si­tive tis­sue at the back of the eye.

In a nor­mal eye, light pass­es through the trans­par­ent lens to the reti­na. Once it reach­es the reti­na, light is changed into nerve sig­nals that are sent to the brain.

The lens must be clear for the reti­na to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred.

Are there oth­er types of cataract?

Yes. Although most cataracts are relat­ed to aging, there are oth­er types of cataract:

  • Sec­ondary cataract. Cataracts can form after surgery for oth­er eye prob­lems, such as glau­co­ma. Cataracts also can devel­op in peo­ple who have oth­er health prob­lems, such as dia­betes. Cataracts are some­times linked to steroid use.
  • Trau­mat­ic cataract. Cataracts can devel­op after an eye injury, some­times years later.
  • Con­gen­i­tal cataract. Some babies are born with cataracts or devel­op them in child­hood, often in both eyes. These cataracts may be so small that they do not affect vision. If they do, the lens­es may need to be removed.
  • Radi­a­tion cataract. Cataracts can devel­op after expo­sure to some types of radiation.

What caus­es cataracts?

The lens lies behind the iris and the pupil. It works much like a cam­era lens. It focus­es light onto the reti­na at the back of the eye, where an image is record­ed. The lens also adjusts the eye­’s focus, let­ting us see things clear­ly both up close and far away. The lens is made of most­ly water and pro­tein. The pro­tein is arranged in a pre­cise way that keeps the lens clear and lets light pass through it.

But as we age, some of the pro­tein may clump togeth­er and start to cloud a small area of the lens. This is a cataract. Over time, the cataract may grow larg­er and cloud more of the lens, mak­ing it hard­er to see.

Researchers sus­pect that there are sev­er­al caus­es of cataract, such as smok­ing and dia­betes. Or, it may be that the pro­tein in the lens just changes from the wear and tear it takes over the years.

When are you most like­ly to have a cataract?

The term age-relat­ed” is a lit­tle mis­lead­ing. You don’t have to be a senior cit­i­zen to get this type of cataract. In fact, peo­ple can have an age-relat­ed cataract in their 40s and 50s. But dur­ing mid­dle age, most cataracts are small and do not affect vision. It is after age 60 that most cataracts steal vision.

Who is at risk for cataract?

The risk of cataract increas­es as you get old­er. Oth­er risk fac­tors for cataract include:

  • Cer­tain dis­eases such as diabetes.
  • Per­son­al behav­ior such as smok­ing and alco­hol use.
  • The envi­ron­ment such as pro­longed expo­sure to sunlight.

Symp­toms and Detection

What are the symp­toms of a cataract?

The most com­mon symp­toms of a cataract are:

  • Cloudy or blur­ry vision.
  • Col­ors seem faded.
  • Glare. Head­lights, lamps, or sun­light may appear too bright. A halo may appear around lights.
  • Poor night vision.
  • Dou­ble vision or mul­ti­ple images in one eye. (This symp­tom may clear as the cataract gets larger.)
  • Fre­quent pre­scrip­tion changes in your eye­glass­es or con­tact lenses.
  • These symp­toms also can be a sign of oth­er eye prob­lems. If you have any of these symp­toms, check with your eye care professional.

How is a cataract detected?

Cataract is detect­ed through a com­pre­hen­sive eye exam that includes:

Visu­al acu­ity test. This eye chart test mea­sures how well you see at var­i­ous dis­tances.
Dilat­ed eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. Your eye care pro­fes­sion­al uses a spe­cial mag­ni­fy­ing lens to exam­ine your reti­na and optic nerve for signs of dam­age and oth­er eye prob­lems. After the exam, your close-up vision may remain blurred for sev­er­al hours.
Tonom­e­try. An instru­ment mea­sures the pres­sure inside the eye. Numb­ing drops may be applied to your eye for this test.

Your eye care pro­fes­sion­al also may do oth­er tests to learn more about the struc­ture and health of your eye.

NOTE: This infor­ma­tion was devel­oped by the Nation­al Eye Insti­tute or pro­vid­ed by med­line plus to help patients and their fam­i­lies search for gen­er­al infor­ma­tion eye dis­eases and con­di­tions. An eye care pro­fes­sion­al who has exam­ined the patien­t’s eyes and is famil­iar with his or her med­ical his­to­ry is the best per­son to answer spe­cif­ic questions.

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