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Pterygium- Prevention of an Insect Wing on the Eye

December 13, 2012

Roshni Ranjit BS, BA1, Scott Jones MD2


1 University of South Florida Eye Institute, University of South Florida Morsani College of Medicine, Tampa, FL
2 Tulane University School of Medicine, Ophthalmology Department

Pterygium is a non-cancerous growth of the conjunctiva, which is the clear, thin tissue that lies over the white portion of the eye (sclera). Although it is a benign growth, it can threaten visual acuity as it approaches the cornea (the anterior wall of the eye), and begins to obscure the line of sight. Pterygium is defined as a fibrovascular wedge of conjunctival tissue that grows over the cornea and usually extends from the nasal portion of the conjunctiva laterally onto the cornea. The word pterygium refers to the shape of the tissue which resembles an insect wing. It is most commonly seen in patients with chronic exposure to ultraviolet (UV) light in sunlight, dust and wind. Pterygium is rarely found in children. It is often painless, but its abnormal appearance is often concerning to patients. However, the area of raised white tissue lined with blood vessels can become inflamed and irritated causing irritation, burning sensation, and/or redness. Pterygia can range in severity by causing no visual symptoms to significant visual impairment. A growth extending more than a few millimeters onto the cornea can impair vision by causing astigmatism, which is a refractive error in which light rays are focused unevenly. Worldwide the prevalence of pterygium varies from 1-25 percent, depending on climate and latitude. It occurs most commonly in tropical and dry sunny regions. The exact pathogenesis remains unknown, but it has been theorized that an inciting factor like UV radiation can trigger a cascade of events which damage the cellular components causing actinic changes of the extracellular matrix. The role of hereditary factors is unknown. The unique characteristic of pterygium is that it may remain in an inactive form for years and then undergo a process of reactivation and produce the symptoms stated above.

Treatment includes symptomatic management of irritation and redness with artificial tears and ocular lubricants for mild disease. For more severe disease, surgical excision can offer relief. The decision to undergo surgical excision varies based on the rate of growth, degree of induced astigmatism, and ocular irritation. Surgical removal is often advised if the fibrovascular tissue has grown far enough onto the cornea to threaten vision. It can also be removed for cosmetic purposes as well. Removal may take place in a procedure room in clinic or in operating room setting. During the procedure, the pterygium is carefully dissected away from the visual axis. An antimetabolite such as mitomycin c or 5-fluoruracil may be applied to the surgical site to reduce recurrence. And finally, a conjunctival graft or amniotic membrane graft may be used to patch the area of resection. Postoperatively, ophthalmologists may recommend some steroid eye drops for several weeks to decrease the inflammation and prevent regrowth of the pterygium. Surgery should be avoided for cosmetic reasons alone because pterygium is likely to recur and can cause irritating symptoms. Recurrence rates fluctuate greatly and occur most commonly within 4 months after the primary pterygium excision. Recurrences and repeated excisions can lead to disruption of the ocular surface which can lead to severe complications of the corneal surface. The most important preventative measure to avoid pterygium formation is to reduce sun exposure, protection against UV light, and ocular lubrication with tears, gels, or ointments.

References

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