Success is about having more options. More the options, more the success. Pterygium remains the most notorious of eye ailments due to its propensity for recurrences. This article highlights the causes, prevention and treatment options for this ophthalmic enigma.
Pterygium or Surfer's eye is a triangular,fleshy mass of conjuctiva 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%.Studies suggest an association with chronic exposure to Ultra-violet B radiations. Localized limbal stem cell anomalies, human papilloma virus 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 aetio-pathogenesis of pterygium help us in deciding the management strategies.
Though all aspects of pterygium still remain an enigma, they do not pose practical problems. It can be diagnosed with certainty whenever encountered. Probe test can easily differentiate it from pseudo-pterygium, its chief differential. And, cyto-pathological evaluation by conjunctival impression cytology (CIC) differentiates it from conjunctival intra-eipthelial neoplasia (CIN). Similarly, treatment is not a practical problem either due to availability of plethora of easy, simple, time-efficient surgical options.
What makes this seemingly trivial lesion gain so much popularity in ophthalmic circles is its notoriety for recurrences.
Indications for Surgery :
Surgical Treatment of Primary Pterygial Tissue :
Removal of the pterygium involves avulsion or excision of the pterygium starting with its head attached to 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.
Recurrence Prevention Measures :
In view of the high recurrence rate of bare sclera technique, various adjunctive measures 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- 0.04% intraoperative mitomycin C for 3 min are less effective than 5 min application. But increasing the duration and concentration may lead to a higher risk of complications such as scleral perforations, scleritis, scleral necrosis, and endophthalmitis.
Postoperative 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 5-14 days (concentrations used range from (0.005 to0.04%). Studies concluded that mitomycin C postoperatively for shorter duration (7days vs14 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 :
Intra-operative Dauxorubicin(0.02% for 3 mins) , daunoribicin(0.02%), cyclosporine A (1%) eye-drops, thiotepa(0.05%) eye-drops and 5-fluoro-uracil(5% for 5 mins intra-op and 1-3 mg intralesional injections into recurrent pterygia) are the other medical options shown to have promising results in recurrence prevention in various studies. Off-late, sub-conjunctival anti-VEGF Bevacizumab(1.25-2mg) therapy has also been proposed for the aforesaid.
Regimes of beta-irradiation advocated for recurrence prevention are:
It has a higher recurrence rate than postoperative mitomycin C eye drops.
The standard technique is a strontium (Sr90) brachytherapy with an epibulbar plaque which has central radioactive disc and non active rim of 2mm.
Surgical Methods :
The following surgical options are currently available with varying success and recurrence rates:
Conjunctival autografts - This is considered to be the procedure of choice for the treatment of primary and recurrent pterygium.
Limbal and limbal–conjunctival transplantation - Since limbal stem cell anomalies have been incriminated in the recent aetio-pathogenetic 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 recurrence.
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%.
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 excision of extensive pterygium.
Amniotic membrane transplantation - Anti-angiogenic, anti-inflammatory and anti-fibrotic properties of amniotic membrane are utilized in treating pterygium. It can be used in 3 forms:
Cultivated conjunctival transplantation - This involves using an ex-vivo expanded conjunctival epithelial sheet on an amniotic membrane substrate.
Lamellar keratoplasty -Its role is mainly limited to replace thinned and scarred corneal tissue after pterygium excision and act as a barrier against pterygium recurrence. Recurrence rates range from 6-100%.
Fibrin glue has the advantage of lesser operating time but recurrences range upto 5-6%.
Pterygium recurrence is still quite rampant. As such, preventive measures like avoiding exposure to ultra-violet 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.
Last reviewed at:
07 Sep 2018 - 5 min read
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