A cataract refers to clouded lens in the eye which affect vision. The lens is the transparent area of the eye that helps to focus light on the retina. Cataract prevents light from reaching the retina. Hence, a person will see blurry images if the lens is cloudy. Cataracts are very common in elderly people.

The lens is made up of water and protein. As people age, clumps of protein group together and reduce the light reaching the retina. Initially, only a small part of the eye is affected. It may not even be noticeable. Gradually, vision worsens because cataracts take time to grow. The clear lens develops a brown tint which makes it difficult for a person to read and undertake routine activities. People who have advanced lens discoloration may not be able to identify blue and purple. 

A person can develop a cataract in their 40s and 50s. However, it may not affect vision. Problems with vision due to cataracts usually begin with people in their 60s. 

A cataract that develops in children, whether congenital (at birth) or acquired, can lead to amblyopia (lazy eye). Hence, immediate treatment is required to prevent loss of vision.


Cataracts are classified into:

  • Secondary cataract

It affects those who have undergone surgery for cataract and other conditions like glaucoma. Steroid use can cause cataract too. People with other health issues like diabetes are also at risk of developing secondary cataract.

  • Radiation cataract

Exposing the eyes to some types of radiation can cause cataract.

  • Congenital cataract

It refers to cataract which develops in both eyes of children. Some babies are born with cataract. This cataract may be too small to affect vision. However, the lens is removed if it affects vision.

  • Traumatic cataract

Should an injury occur in the eye, a cataract can develop. 

Other classifications include age-related types:

  • Nuclear cataract

This cataract is found in the center of the eye. 

  • Cortical cataract

The cataract affects the layer of the lens surrounding the nucleus.

  • Posterior Subcapsular Cataract

This one is located in the back; outer layer of the lens.

Causes and Risk Factors

A cataract is caused by the clumping together of protein in the lens of aging people. When clumping happens, the protein forms a cloud on a small part of the lens. With time, the cloud may grow larger and block the lens from seeing. The lens functions as a camera by focusing light on the retina. It also adjusts the eye’s focus permitting it to see images both near and far. With the lens blocked, a person’s vision is significantly affected. 

Cataracts are very rare in children. However, a child can develop it if the pregnant mother has an infection such as rubella. Cataracts may also be hereditary.

Certain drugs such as corticosteroids may cause cataracts. It is also believed to be caused by diabetes, smoking, and alcohol. Nutrition devoid of antioxidants may cause cataract.

Another cause may be protein in the lens aging which leads to clumping together of protein.

Prolonged exposure to ultraviolet rays is may also cause cataract.

Retinal detachment (when tissue on the retina pulls away from its normal position) may cause a cataract.

Signs & Symptoms

Symptoms of cataracts include:

  • Poor night vision
  • Glare (extra sensitivity to light)
  • Frequent changes in prescriptions for glasses or lenses
  • Blurry or cloudy vision.
  • Multiple images in one eye 
  • Loss of ability to discern colors


Cataract is diagnosed through:

  • Dilated eye examination

The eye care professional will place drops in the eyes to dilate the pupils. He will then use a special magnifying glass to establish the damage on the retina and optic nerve. This examination may cause blurred images in the eyes for several hours.

  • Slit-Lamp exam

The professional examines the cornea, iris, lens, and other front parts of the eye.

  • Eye pressure measurement

Tonometry is an instrument used to measure the pressure inside the eye. Numbing drops may also be applied in the eyes for the test. 

  • Visual acuity examination

The patient will be required to read from a chart to test vision at various distances.

  • Lens evaluation

The lens is subjected to high magnification and illumination to locate the cataract. This action also determines its severity. 

  • Supplemental Testing

He/she may conduct a test to determine the structure and health of the eye. The examination also includes color vision and glare sensitivity.


Treatment for cataract is directed towards removing the cloudy lens and substituting it with an artificial lens.

Medical Treatment

In its early stages, it can be treated by changing the eyeglass prescription. Anti-glare sunglasses help to reduce the glare for night driving. Brighter lighting is beneficial for reading. 

Surgical Treatment

An operation is only recommended when vision loss affects a patient’s daily tasks such as driving, reading and others. 

Cataracts that interfere with vision in children should be removed as soon as it is safe to do so. The removal prevents interference with the normal development of the vision centers in the brain.

Sometimes cataracts that don’t interfere with vision may also need to be removed. This happens when the cataract prevents treatment of other age-related eye conditions like diabetic retinopathy and macular degeneration. 

Surgery is never performed on both eyes at once. Usually, there is a four-week interval between the two operations.

Though rare, loss of vision, double vision, infections, low and high eye pressure, inflammation, and bleeding can result from cataract surgery. However, if detected promptly, it can be treated successfully. 

After-cataracts can develop months or years after surgery. Here, the eye tissue with the intraocular lens (IOL) gets cloudy, causing blurred images. IOLs are clear artificial lenses. Laser treatment is recommended for after-cataracts.

Prognosis/Long-term outlook

Cataract surgery is common, safe, and effective. About 90% of patients experience better vision after surgery. Also, the artificial lens inserted requires no care.

After surgery, images may appear blurry for a while because the eye takes time to heal. Usually, it takes about eight weeks to experience complete healing.

If treatment is sought early for children, the outcome is usually good.

Prevention/Follow Up

  • People should wear UV blocking lenses. It  may delay the onset of cataracts. 
  • Healthy eating that includes green-leafy vegetables and foods abundant in antioxidants. 
  • Smoking is discouraged. 
  • People aged 60 and above should have a dilated exam once every alternate year. 
  • Those aged 65 and above can have the examination annually.

Children need ongoing treatment to repair eye-brain connections. This means teaching the eye how to focus well. The children might need a combination of contact lenses, IOLs, or glasses. Patching (covering the stronger eye to stimulate vision in the weaker eye) is necessary if amblyopia has developed in an eye. For successful outcomes, years of individualized visual rehabilitation are required.