Eye Health

Updated 07 March 2018

What are cataracts?

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


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

The lens of the eye focuses light, so that you 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 and cloud 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 most often it is after the age of 60 that cataracts typically start to impede vision.

Cataracts are the leading cause of blindness worldwide, accounting for almost 20 million cases, and the number is projected to reach 40 million by the year 2020. Despite these numbers, the disease is one of the less serious eye disorders, as surgery can restore lost vision in most cases.


A cataract has little effect on vision at first. Often cataracts develop so slowly that you are unaware of them. If the cataract is on the outer edge of the lens, no change in vision may be noticed. Cloudiness near the centre of the lens usually interferes with sight.

Small cataracts that do not affect vision may not require treatment. However, cataracts progress and become larger or denser, progressively clouding the lens and causing significant vision changes.

Severe cataracts can interfere with an independent lifestyle by preventing older adults from performing normal activities. Eventually the entire lens becomes white and will cause blindness, which is usually reversible with an operation. Glaucoma or inflammation can be a complication of advanced cataracts.

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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