Eye Health

22 November 2010

Pterygium, the filmy membrane

Many South Africans have a thin, filmy membrane with tiny surface blood vessels on the white of their eye, extending from the nasal side towards their iris.


Many South Africans have a thin, filmy membrane with tiny surface blood vessels on the white of their eye, extending from the nasal side towards their iris. This triangular shaped thickening is called a pterygium and can spread towards and over the cornea to obstruct vision.

There are many popular theories about the causes of a pterygium, such as irritants and sunlight and dust, but none of them has been proved with any certainty.

A pterygium tends to goes through active, inflamed phases and quiet phases over months to years as it slowly grows onto the cornea: it usually appears during adolescence or early adulthood and grow slowly for a number of years before becoming smaller and inactive.

Symptoms of irritation such as redness, burning, scratching, dryness and itch are common and are nothing to worry about if they occur only occasionally and are not too severe. Symptoms tend to be more troublesome in the early years when the pterygium is actively growing.

Self treatment

The pterygium itself is normally harmless and treatment is purely to relieve symptoms when they occur. A pterygium often causes a dry eye problem, and most symptoms tend to be relieved by an artificial tear drop.

For itch try an over-the-counter antihistamine drop, taking care to use it exactly as directed. If redness is a prominent feature, a decongestant eye drop is usually effective in relieving the symptoms. However, there is a very real danger of aggravating the problem with decongestant drops, and they should be used as infrequently as possible and only for short periods.

Lubricants and sunglasses provide relief of symptoms, but removal by surgery is the only cure. Recurrences are fairly common.

See your ophthalmologist if

  • Your symptoms are not adequately relieved by the eye drops above.
  • Your symptoms recur frequently.
  • There is pus in the eye or the eyelids stick together on waking in the morning.
  • The pterygium covers part of the iris and grows onto the cornea and towards the pupil.
  • You have any deterioration of vision.
  • You would like the pterygium to be removed for cosmetic reasons.

Occasionally a pterygium produces unacceptable problems and needs to be removed surgically. Surgery is generally quite successful, but sometimes the pterygium grows back even more aggressively after surgery, and so surgery should not be undertaken without good reason.

Reviewed by Dr Clive Novis, Ophthalmologist, (November 2010)

Useful resources:

South African Optometric Association
Tel: 011 805 4517

South African National Council for the Blind
Tel: 012 452 3811

Retina South Africa
Tel: 011 622 4904

Ophthalmological Society of South Africa


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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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