Pterygium (pronounced: ter ig' ee um)
| Pterygium (pronounced: ter ig' ee um) |
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| Date: October 22, 2006 | |
A pterygium is a growth of scar tissue and blood vessels on the exposed surface of the eye in response to ultraviolet damage from the environment. A pterygium often grows in a "wing" shape (pterygos in Greek is wing), which extends across the cornea towards the pupil. It most often occurs on the nasal side of the pupil. While the redness can be aggravated by wind and other external irritants, it is U.V. damage that causes the permanent growth onto the cornea. The mechanism behind pterygium formation is the following. Solar radiation includes visible light and ultraviolet energy (which is not visible) that is harmful to the exposed parts of the body. The outer surface of the eye is covered with a layer of cells known as epithelium. The epithelium on the eye is more sensitive to ultraviolet damage than the corresponding epithelium of the skin because it does not have the protective coating known as keratin (the scaly layer that builds up in a callous). If the epithelial cells and basement membrane on which they rest are damaged by ultraviolet radiation, a healing response is triggered. This healing response involves the release of enzymes which "dissolve" the damaged tissue, and growth factors that stimulate the growth of new tissue. After the basement membrane is damaged a response similar to scar formation occurs. This "drags" the abnormally thick epithelium across the cornea and stretches the adjacent conjunctiva. Given the same exposure different people will develop different responses due to individual variations in enzyme levels in their tears. The best treatment is prevention. Wearing wrap around sunglasses when exposed to sun and wind can prevent a pterygium as well as skin cancer of the eyelid (since sun-screening cream cannot be applied at the lid margin), and may delay the onset of cataract and age-related macular degeneration. If the eyes are reddened from a day outdoors the appropriate action is to use artificial tears frequently and decongestant "get the red out" drops infrequently. Artificial tears help the eye to recover. Preservative-free or single unit dosed are best. Decongestant drops simply disguise the redness while the pterygium grows. If the eyes are reddened for days at a time and do not improve by avoiding irritants and using artificial tears, then anti-inflammatory prescription medication should be considered, since the prolonged vascular response may eventually produce permanent changes in the blood vessels. If a pterygium grows across the pupil you have already left it too late to save clear vision. Beneath the pterygium is a scar which may be quite deep and cannot be completely removed. If the pterygium is outside the pupil, any faint remaining scar that is not cosmetically visible is of no importance. However, if the remaining scar is in the pupil, the vision is affected permanently. The best time to have a pterygium excised is before it reaches the nearest edge of the pupil. Some believe the best time of year to achieve a good cosmetic result is during winter months when sunlight exposure is at a minimum. The complications of pterygium removal include regrowth, ulceration within the operated area, and infections. A change in vision can occur if the pterygium extends close to the pupil or if scarring produces astigmatism or night glare. Complications can be avoided if the eye is protected from irritants and kept well lubricated during the healing period. In addition, timing is very important to avoid scarring in the visual axis. If you have a pterygium you should see your Optometrist on a regular basis (minimum yearly) for photo documentation. Artificial tears and sunglasses should be used on a daily basis. In the event the pterygium becomes inflamed (pterygiumitis), short term use of topical steroid drops should be considered. If you have questions concerning this condition or think you may have a pterygium, please contact our offices in Stillwater at 405-372-1715 or Pawnee at 918-762-2573. |
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