What is a Pterygium?
Pterygium (plural pterygia) is the term we give to a common, usually vaguely triangular, fibrovascular growth over the surface of the cornea. The name is derived from the Greek word ‘Ptéryx” which means wing and ‘ion’ which means little. The ancients perhaps noticed a similarity with the appearance of insect’s wings.
What causes Pterygia?
Pterygia arise due to environmental irritation to the surface of the eye, particularly exposure to ultraviolet light and are common in New Zealand amongst people who spend a lot of time out of doors, particularly with water sports. The process of pterygium formation usually begins as an area of yellowish thickening of the conjunctiva on the nasal side of the white of the eye called a pinguecula. The thickening of the tissue causes problems with the tear film resulting in localised areas of dryness and inflammation of the tissues which sets up a reaction leading to the growth of tissue across the cornea. Once it has grown across the cornea it becomes a pterygium.
What problems do Pterygia cause?
Small, relatively flat pterygia are often asymptomatic and are simply a cosmetic issue. As they become larger or thicker they frequently cause persistent irritation and may grow far enough across the cornea to affect the vision.
How are Pterygia treated?
Treatment of Pterygia can be divided into two categories – conservative and surgical.
Conservative treatment involves the use of a hat and sunglasses to reduce the environmental exposure of the eye, along with lubricant or decongestant drops, and sometimes more powerful anti-inflammatory drops including steroid and non-steroidal medications. For smaller pterygia these measures may be sufficient. Care should be taken with the use of decongestant drops as some people will develop reactions to them which can even cause the irritation and inflammation to increase. This is a particular problem if people use decongestant drops frequently. Steroid drops have potential adverse side effects and should not be used without supervision and are typically only recommended for short term use.
Surgical treatment: If conservative measures do not prove sufficient, or a pterygium has grown so far across the cornea that it is considered a threat to the vision, surgery is possible for Pterygia. The surgical removal of pterygia is usually done under local anaesthetic on a day case basis and takes about 30 minutes. Prior to surgery local anaesthetic drops or gel are applied to numb the eye and a small injection of local anaesthetic is administered. These are generally very effective, and it is unusual for the operation itself to be painful.
Once the anaesthetic has taken effect, the pterygium is removed from the surface of the eye and then a similar sized piece of conjunctival tissue is harvested from beneath the upper eyelid and secured into position either with tiny sutures, surgical glue, or a combination of the two.
It is common for there to be significant discomfort postoperatively – particularly over the first 24 hours. This is controlled by the use of anaesthetic gel, and oral analgesics. Occasionally an injection of painkillers may be necessary.
The vast majority of pterygium operations give good results. Occasionally the grafts may detach from the surface of the eye and a proportion of pterygia will recur, particularly in younger people who continue to be exposed to high levels of ultra-violet light.