Pterygium
What is it?
PA Pterygium (‘wing of tissue’) is an overgrowth of the conjuctiva that usually only covers the white of the eye onto the cornea. It usually presents in patients over the age of 45, although it has been known to occur during younger years. This is not a cancer as it is a discrete abnormality on the external surface of the eye.
Pterygium can grow at varying rates. They can grow rapidly, slowly, regress spontaneously and restart growing after a long period of time. Occasionally, it may encroach the pupil and enter the line of vision. Pterygium may grow on both eyes but they rarely grow more than once per eye.
Causes?
Pterygia seem to be particularly common in Queensland. Queenslanders have one of the highest reported rates of occurrence in the world (up to 10%).
Some risk factors include:
- Excessive sunlight exposure in the first 10 years of life.
- Living in a dry and/or dusty environment.
Symptoms?
Most patients have no symptoms. Patients do sometimes experience:
- Dry Eyes
- Ocular Irritation
- Cosmetic changes, from the reddish lesion
Decrease in vision (Directly – If covering the line of sight. Indirectly – Changing the shape of the cornea.)
Significant numbers of patients complain of dry eyes and ocular irritation. This can actually predate the onset of the Pterygium. Others are just aware of the cosmetic disfigurement caused by the reddish wing like lesion growing onto the clear part of the front of the eye (the cornea).
Air conditioning, lack of sleep, sunlight, night shifts, and smoke can all aggravate a Pterygium increasing symptoms and redness.
It is important to note that a Pterygium can reduce vision indirectly by deforming the cornea (astigmatism) or directly by covering the direct line of sight through the pupil.
Treatment
In most cases, no intervention is required. They generally don’t regress and patients should monitor any changes at home. If there are concerns about recent growth, this is a prompt for review by an eye care professional.
In those patients in whom redness is the main issue, the occasional use of an over the counter ‘eye whiteners’ can give temporary relief for important social occasions. Chronic use of these eye drops is not recommended as rebound redness on withdrawing these drops if used chronically.
The use of artificial tears (especially preservative free preparations) can achieve a similar if slower relief of irritation and redness and are often under used, even in eyes without dry eye symptoms.
Surgical excision of Pterygia is indicated for either cosmetic reasons or visual interference. In cases where surgery is undertaken to eradicate symptoms of irritation and dryness, these outcomes are less successful. This is because those symptoms generally predate Pterygium development and they can persist after removal.
The major complication is re-occurrence of the Pterygium. Simple excision re-occurrence rates have been reported as high as 40%. For excision with more advanced techniques, it is between 5 to 15%.
One such modern technique is to combine Pterygium removal with a conjunctival auto-graft along with wide dissection of tenons. The graft is secured with tissue glue from underneath the upper lid area which protects it from U.V sunlight. These all help improve clearance rate to ensure re-occurrence rates are as low as possible.
This pterygium extends to the pupil margin (a+b) however detailed mapping (c) shows a flattening effect of over 8 Dioptres encroaching the central visual axis and far past the pupil depicted as the dotted line. This impacts the vision particularly at night when the pupil is more dilated and more of the pterygium interferes with the enlarged central visual axis. Removal of the pterygium (d+e) removed the troublesome aberrations (f) in the vision and simplified his spectacle prescription.
Pterygium removal utilised a conjunctival graft prepared from non sun damaged conjunctiva under the upper lid. Using a conjunctival graft to cover the defect left after pterygium removal is the gold standard of care currently. The arrows (e) delineate the graft edge. This has been proven to reduce the pterygium recurrence rate from around 40-50% to less than 5%. This pterygium was secured using a tissue glue (d+e) rather than sutures which provides more comfort postoperatively. There is also some weak published evidence to suggest that the tissue glue may also reduce the chance of a recurrence even further compared to using sutures (2%).
How to prevent the occurrence of Pterygia?
Prevention is better than cure.
Things you can do to help reduce your risk of Pterygia include:
- Wearing sunglasses when possible. It is important they are labeled as compliant with Australian Standard (AS 1067.1 1990 Sunglasses and Fashion Spectacles). Also look for an EPF UV rating of either 9 or 10; these lenses transmit minimal UV radiation.
- Children should be kept out of the midday sun. For school children particularly of primary school age, sunglasses should be worn outdoors. Kids of all ages should wear broad-brimmed hats, strollers and baby buggies should have a sun visor and kids wear appropriate sunglasses from the earliest age coaxible.
