Eye Health

Updated 26 September 2018

What are cataracts?

Cataracts refer to clouding of the normally clear lens portion of the eye. This is a gradual process that can eventually impair vision.

A cataract is clouding of the normally clear lens portion of the eye – a gradual process that can eventually impair vision.

The lens of the eye focuses light, so that we can see objects clearly at different distances. It must remain transparent for clear vision. The lens is mostly made up of water and protein, in a precise composition to keep the lens clear and allow light to pass through.

With age, changes in the chemical composition of the lens occur: parts of the protein may clump together and start to cloud a small area of the lens. This is how most cataracts are formed.

Over time, the cataract may grow larger, clouding more of the lens. As the developing cataract blocks or distorts light entering the eye, those affected will experience a gradual, persistent and painless blurring of vision.

Everyone eventually gets cataracts if they live long enough. The lens can start clouding at any age, but cataracts typically start to impede vision after the age of 60.

Cataract is the leading cause of blindness worldwide and responsible for 51% of world blindness, which represents about 20 million people. Cataract is also the leading cause of blindness in South Africa. Here, it’s responsible for about 50% of blindness.

Despite these numbers, the disease is one of the less serious eye disorders, as surgery can restore lost vision in most cases.

Reviewed by ophthalmologist Dr Viresh Dullabh, MBBCh (Wits) FC Ophth SA (CMSA) MMED (UKZN). September 2018.

Read more:

Symptoms of cataracts

Causes of cataracts

Diagnosing cataracts


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Megan Goodman qualified as an optometrist from the University of Johannesburg. She has recently completed a Masters degree in Clinical Epidemiology at Stellenbosch University. She has a keen interest in ocular pathology and evidence based medicine as well as contact lenses.

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