Preoperative Subpterygeal Injection Versus Intraoperative Mitomycin C for Pterygium Removal: Comparison of Results and Complications

We read the article by Khakshoor and associates 1 with keen interest. We wish to express the following comments.

Recurrence of pterygium remains the most enigmatic complication of pterygium surgery. Subconjunctival mitomycin C (MMC) one month before bare sclera excision of pterygium appears to be a promising new technique in the armamentarium of ophthalmologists, with recurrence rates of 0% to 6%. The experience with this technique is still very limited. We appreciate the authors for this commendable research work. Although the technique is simple, quick, and not associated with any recurrence, it is a 2-stage procedure and is associated with persistent whitening of sclera and hypovascularity at the site of excision in 5.5% of patients. We wonder whether persistent whitening of sclera 1 was the result of higher concentration of MMC (0.02%) used and subpterygial injection compared to the study by Donnenfeld and associates, in which 0.015% MMC was injected subconjunctivally one month before bare sclera excision with a recurrence rate of 6%. It seems that in subpterygial injection, MMC would be delivered between sclera and pterygial tissue, whereas in subconjunctival injection MMC would be delivered between conjunctiva and pterygial tissue; thus a higher concentration of MMC reaches the sclera, causing ischemia of episcleral vascular plexus and whitening of sclera and hypovascularity at the site of excision. Intrapterygial injection of MMC is suggested as another alternative to avoid sclera whitening.

Mean age of patients in this study was higher (48.48 years), which might have contributed to reduced recurrence. It is well established that the recurrence after pterygium surgery decreases with increasing age of patients. Most of the recurrences occur in patients under 35 to 40 years of age. The authors 1 did not observe any complications associated with intraoperative MMC 3 in group B. Rotational conjunctival flap appears to have a protective effect in preventing MMC-related complications. Even a high dose of 1 mg of MMC subconjunctival injection did not cause significant local side effects except local thinning of the conjunctiva with lack of superficial vessels. It could be explained because of presence of intact conjunctival covering over sclera. Avisar and associates reported that leaving the whole sclera uncovered in pterygium surgery places patients at high risk of complications and recurrence. We, therefore, propose to cover the bare sclera with rotational conjunctival flap or conjunctival autograft even in patients undergoing bare sclera excision 1 month after intrapterygial injection of MMC to prevent scleral whitening. Additionally, rotational conjunctival flap to cover bare sclera would avoid identification of the subpterygial MMC group and observer bias, if any.

The authors have commented that preoperative MMC injection into pterygial neck would protect corneal endothelium. However, as MMC was injected subpterygially, it would mimic MMC application to sclera. MMC 0.02% application to the bare sclera during pterygium surgery has been found to have a deleterious effect on corneal endothelium. However, the effect of MMC on corneal endothelium varies with the concentrations and durations of the drug and the technique of MMC application.

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Jan 16, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Preoperative Subpterygeal Injection Versus Intraoperative Mitomycin C for Pterygium Removal: Comparison of Results and Complications

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