Introduction:
Pterygium or surfer's eye is a triangular, fleshy mass of conjunctiva that also involves the cornea. Pterygium derives its etymological origin from the Greek word 'pterygion,' meaning small wing. In ophthalmic jargon, it is described as a triangular, wing-like fibro-vascular encroachment of degenerative sub-epithelial conjunctiva, straddling the limbus onto the cornea.
Pterygium is a common disorder in many parts of the world, with reported prevalence rates ranging from 0.3 % to 29 %. What makes this seemingly trivial lesion gain so much popularity in ophthalmic circles is its notoriety for recurrences.
What Causes Pterygium?
Studies suggest an association with chronic exposure to ultraviolet B radiations. Localized limbal stem cell anomalies, human papillomavirus (HPV) infection, p53 gene mutations, and imbalance of matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) have been strongly implicated in pterygium causation. These recent insights into the etiopathogenesis of pterygium help us in deciding the management strategies.
What Are the Signs and Symptoms of Pterygium (Surfer's Eye)?
Surfer's eye does not always cause symptoms. If symptoms are seen, they are mild. Some of the common symptoms include:
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Redness.
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Blurred vision.
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Eye irritation.
If the pterygium grows larger and covers the cornea, it can interfere with vision.
How Is Pterygium Diagnosed?
Though all aspects of pterygium still remain an enigma, they do not pose practical problems. It can be diagnosed with certainty whenever encountered. A probe test can easily differentiate it from pseudo-pterygium, its chief differential. And cytopathological evaluation by conjunctival impression cytology (CIC) differentiates it from conjunctival intraepithelial neoplasia (CIN). The other diagnostic tests recommended include:
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Visual Acuity Test:
In this test, the patient is asked to read the letters on an eye chart.
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Corneal Topography:
This test is used to measure the curvature changes in the cornea.
What Are the Indications for Surgery?
Similarly, treatment is not a practical problem due to the easy availability of a plethora and simple, time-efficient surgical options. Indications for surgery to treat pterygium include;
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Visually significant induced astigmatism.
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The threat of involvement of the visual axis.
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Severe symptoms of irritation.
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Cosmesis.
Surgical Treatment of Primary Pterygium Tissue:
Removal of the pterygium involves avulsion or excision of the pterygium starting with its head attached to the cornea followed by its neck and body.
If no additional measures are performed, pterygium excision alone is commonly referred to as bare sclera excision. The recurrence rates for bare sclera excision alone are absurdly high (ranging from 30 % to 80 %), and hence bare sclera excision alone is no longer recommended as a treatment modality.
What Are the Recurrence Prevention Measures?
In view of the high recurrence rate of the bare sclera technique, various adjunctive measures such as medical methods, beta-irradiation, and surgical methods have been advocated to prevent recurrence of the disease.
Mitomycin C Treatment:
Mitomycin C has been used effectively in preventing recurrences of pterygium. It can be used either intraoperatively (carried out in the course of surgery) as sponges applied to the scleral bed after pterygium excision or postoperatively (done after a surgical operation) as topical drops.
Intraoperative Mitomycin C Treatment:
Mitomycin C in concentrations of 0.01 % - 0.04 % is used intraoperatively. Most surgeons recommend a concentration of 0.02 % applied for 3 minutes.
Studies suggest that 0.02 % to 0.04 % intraoperative Mitomycin C for three minutes is less effective than a five-minute application. But increasing the duration and concentration may lead to a higher risk of complications such as scleral perforations, scleritis, scleral necrosis, and endophthalmitis.
Post-Operative Mitomycin C Treatment:
Postoperative Mitomycin C eye drops have also been shown to be effective, with 0.02 % being the commonest concentration used in q.i.d. dosage for 5 to 14 days (concentrations used range from (0.005 % to 0.04 %). Studies concluded that Mitomycin C post-operatively for a shorter duration (7 days vs. 14 days) is equally efficacious with lesser complications.
The recurrence rates for intraoperative Mitomycin C (3 % - 37.9 %) and post-operative Mitomycin C eye drops (0 % - 38 %) have been found to be very similar.
Other Medical Options:
Intraoperative Doxorubicin (0.02 % for 3 minutes), Daunorubicin (0.02 %), Cyclosporine A (1 %) eye-drops, Thiotepa (0.05 %) eye-drops and 5-fluoro-uracil (5 % for 5 minutes intra-operatively and 1 mg to 3 mg intralesional injections into recurrent pterygia) are the other medical options shown to have promising results in recurrence prevention in various studies. Off-late, subconjunctival anti-VEGF Bevacizumab (1.25 mg to 2 mg) therapy has also been proposed for the aforesaid.
Beta-Irradiation:
Regimes of beta-irradiation advocated for recurrence prevention are:
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A single application of beta-irradiation.
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Several applications over consecutive days immediately in the post-operative period.
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Several applications over a 2-week period.
It has a higher recurrence rate than post-operative Mitomycin C eye drops.
The standard technique is a strontium (Sr90) brachytherapy with an epibulbar plaque which has a central radioactive disk and inactive rim of 2 mm.
Surgical Methods:
The following surgical options are currently available with varying success and recurrence rates:
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Conjunctival Autografts - This is considered to be the procedure of choice for the treatment of primary and recurrent pterygium.
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Limbal and Limbal–Conjunctival Transplantation - Since limbal stem cell anomalies have been incriminated in the recent etiopathogenetic mechanisms of pterygium, the concept of conjunctival autograft (limbal–conjunctival graft) emanated, and it was propounded that it may act as a barrier to conjunctival cells migrating onto the corneal surface and help prevent a recurrence.
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Conjunctival Flaps -This entails the use of sliding conjunctival flaps harvested from inferior or superior bulbar conjunctiva to cover the bare sclera. Recurrence rates range from 1 to 5%.
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Conjunctival Rotation Autografting - This involves removal of the pterygium and reversal of the removed conjunctiva so that the most nasal aspect is sutured at the limbus and vice-versa. This is a useful technique for cases in which it is not possible or desirable to use the superior conjunctiva as a donor source, such as with the excision of extensive pterygium.
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Amniotic Membrane Transplantation - Anti-angiogenic, anti-inflammatory, and anti-fibrotic properties of the amniotic membrane is utilized in treating pterygium. It can be used in three forms:
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Conventional, epithelialized cryopreserved human amniotic membrane.
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De-epithelialized.
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Freeze-dried.
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Cultivated Conjunctival Transplantation - This involves using an ex-vivo expanded conjunctival epithelial sheet on an amniotic membrane substrate.
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Lamellar Keratoplasty -Its role is mainly limited to replacing thinned and scarred corneal tissue after pterygium excision and acting as a barrier against pterygium recurrence. Recurrence rates range from 6 % to 100 %. Fibrin glue has the advantage of lesser operating time, but recurrences range up to 5 % to 6 %.
Conclusion:
Pterygium recurrence is still quite rampant. As such, preventive measures like avoiding exposure to ultraviolet radiations, dust, smoke, and pollutants, maintaining adequate eye hygiene and nutrition, and using lubricant eye drops form a major part of eradicating this disorder. After all, prevention is always better than cure.
