A pterygium  (pronounced "te-ridge-e-um") is a growth of thickened tissue that develops on the white part of the eye, usually on the nose side of the eye, and can extend on to the surface of the eye towards the iris (the coloured part of the eye). This growth is often triangular in shape and, if left untreated, it can extend across the pupil obscuring vision or causing the surface of the eye to alter shape and "warp", resulting in blurring of the vision.  Both eyes can be affected.

If a pterygium grows large enough it can affect the vision or cause other symptoms such as redness and irritations.  If this happens, the pterygium may need to be surgically removed.  If a pterygium is not interfering with sight, or causing annoying symptoms, it can be left alone.
A pterygium is not a cancer and usually grows relatively slowly.

Causes of pterygium
A pterygium is almost certainly caused by exposure to excessive amounts of ultraviolet light or to dry, dusty atmospheres.  They are very common in Australasia, especially in people who spend a lot of time outdoors and in ultraviolet light (e.g. farmers, arc welders).

Signs and symptoms
You may notice:

• eye redness and inflammation
• a gritty feeling in the eye
• a feeling that there is a foreign object in the eye
• dryness of the eye due to reduced tear production
• blurring of vision if corneal surface is altered or "warped"
• obscuring of vision if growth encroaches across the pupil.

In the early stages a pterygium may be confused with a pinguecula.

PINGUECULA (pin-gwek'-u-lah): a yellowish lump which develops on the white of the eye.  It can be surgically removed the same way as a pterygium, but this is rarely necessary.

Reasons for removal of a pterygium
They may be removed in the following cases:

• if vision is threatened - if a pterygium grows large it can block or blur vision and may even block the pupil.  If the pterygium is too large, permanent scarring may be left after removal.
• grittiness, discomfort and redness - a pterygium can cause considerable grittiness and redness.  This may be temporarily eased with eye drops, but removal may be necessary if drops do not give symptomatic relief.
• astigmatism - a growing pterygium can pull on the cornea causing astigmatism and reduced vision.
• appearance - the pterygium may be removed if it is cosmetically unsightly.
• contact lenses - a pterygium can interfere with contact lens fitting or the pterygium may be irritated by the edge of the lens.

Pterygium surgery
The operation to remove the pterygium is usually performed using local anaesthetic eye drops and takes 20 - 30 minutes.

The surgeon uses a microscope or loops to visualise the operation site. The pterygium is peeled off the cornea and the scar tissue is removed.  This usually leaves a bare area on the white of the eye.  A section of the conjunctiva (the transparent skin that covers the surface of the eye) is taken from under the eyelid and is grafted onto the area where the pterygium was.  The graft is sutured into place and an application of antibiotic ointment is applied. A paraffin gauze and double eye pad is applied over the closed eye and stays on until the next morning. Instructions will be given on changing pads.  Pads are used for three days. Eye drops and ointment will be prescribed after surgery to prevent infection and assist with healing.  A follow-up appointment is at 6 weeks.

Prevention
In order to prevent or reduce risk of a pterygium forming or recurring it is recommended to:

• use sunglasses that block out ultraviolet light (close fitting wrap around are best)
• wear sunglasses and hat outside
• avoid exposure to environmental irritants e.g. smoke, wind and chemical pollutants
• use appropriate eye safety equipment in work environments.