What is a cataract?

Around half of Australians aged between over 65 to 74 have cataracts. A cataract is a cloudy area in the lens of the eye that interferes with vision by diffusing light as it passes through the eye. Symptoms can include:

  • cloudy or foggy vision
  • blurry or distorted vision
  • changes in colour vision
  • frequent increases in eyeglass or contact lens prescriptions
  • poor night vision (especially affected by headlights)
  • progressive loss of vision
  • halos or glare around lights
  • double vision
  • loss of contrast
  • a white or ‘milky’ spot over the pupil of the eye

A cataract may display a number of different symptoms and be caused by a variety of factors, including age, injury, and certain diseases.

While some people have cataracts at birth or develop them early in life, the majority of cataract diagnoses occur in patients who are in their 60s or 70s.

How do cataracts develop?

Cataract symptoms may appear slowly and painlessly, but often require treatment as they progressively obstruct vision.

A cataract is a loss of clarity within the lens of the eye. A normal lens is clear and lets light pass to the back of the eye.

  • The eye works like a camera
  • Normal human lens focuses light clearly on the retina
  • Cloudy lens (cataract) keeps light from focusing clearly on the retina

CataractWhen a cataract forms in the lens it blocks some of the light. As it develops, it becomes harder for a person to see.

Different types of cataracts

There are several types of cataracts:

Age Related Cataract

Nuclear Sclerosis
This is a hard cataract. The lens becomes hard and yellow as it ages. This usually progresses slowly over time. This type of cataract causes greater impairment of distance vision than near vision. In the early stages, the hardening of the lens causes the refractive power to change causing the lens to become myopic or nearsighted. In some cases patients are able to read without their eyeglasses, this condition is called second sight.

This is a peripheral cataract. The cloudiness is located near the outer edges of the lens. The effect on vision varies depending on the location of the cloudiness on the lens. A common symptom is glare from light sources such as headlights of oncoming cars. Cortical cataracts vary greatly in their rate of progression.

Posterior Subcapsular
This cloudiness begins at the very back layer of the lens. This usually occurs in younger patients. The common symptoms are glare and poor vision in brightly lit conditions. Near vision tends to reduce more than distance vision. In addition to being one of the main types of age-related cataracts, posterior subcapsular cataracts can occur as a result of trauma, corticosteroid use and exposure to radiation.

Congenital Cataract

These are present at birth. This type of cataract occurs in 1 out of 2000 births. These cataracts may not affect vision. If they do, they may need to be removed. The main reasons these occur are usually the child has an associated syndrome with this, may be inherited and one third are due to undetermined causes.

Secondary Cataract

When doing cataract surgery, the surgeon removes the inner portions of the lens. The outside layer of the lens, called the capsule is left in place to hold the artificial implanted lens. This outer layer can become cloudy and cause visual disturbance. This secondary clouding is called a secondary cataract. The onset of a secondary cataract can occur within months or years after cataract surgery. It usually occurs in both eyes. This type of cataract is easily treated by laser.

Traumatic Cataract

This type of cataract is a result of either, an injury by physical force, radiation, electrical current, chemicals or disease such as diabetes. These may become present right after the injury or years later.

Causes of cataracts

Most cataracts develop as people get older, and usually they are first noticed around the age of 50-60. The reason why is not yet known. One theory is that it is caused by a disturbance in the fluids and nutrients in the lens.

In younger people there are certain factors that can increase your risk of getting cataracts. These include:

  • diabetes - this can cause a secondary cataract to develop
  • an injury to the eye
  • exposure to ultraviolet light from sunlight
  • medication use such as long-term use of steroid tablets
  • smoking
  • heavy drinking
  • a family history of cataracts

Who develops cataracts?

  • Almost everyone will develop cataracts as they grow older.
  • Typically, people in their sixties and most people over age seventy have some degree of cataracts.

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