Eyeworld

69 EW CORNEA July 2016 Two scleral melts after pterygium surgery with MMC Source (all): W. Barry Lee, MD specially prepared. "I've seen phy- sicians make concentration errors," he said, adding that this is where it can be helpful to have an experi- enced compounding pharmacy mix it. "We're lucky enough to have a compounding pharmacy right in our surgery center, so when we're doing PRKs or lamellar keratectomies, it's nice to go next door, and they make it up for us and give it to us that morning." While the drug Mitosol (Mobius Therapeutics, St. Louis) is commer- cially available at traditional phar- macies, Dr. Lee finds that this can at times be difficult to obtain. "The problem is that it gets back-ordered a lot, so in my experience it's been hard to get that dependably." To avoid complications, Dr. Rapuano stressed the importance of keeping MMC away from the limbus and the conjunctiva, when used in conjunction with excimer laser surgery. "It's applied just on the cornea," he said. "You don't want there to be too much of the mitomy- cin liquid on the sponge because it will drip off and go where you don't want it to." Ideally, the physician wants the sponge to be moist, but not super wet. "I suck it up off the sponge right before I'm going to re- move it from the eye," Dr. Rapuano said, adding that he uses a dry Weck- Cel sponge to remove any excess that might otherwise spill onto the conjunctiva. He then irrigates the area with 2 bottles of saline. As long as physicians keep the MMC on the cornea following ex- cimer laser surgery without spilling into other areas, there should be very little chance of a patient ending up with limbal stem cell deficiency, Dr. Rapuano noted. This is some- thing to be particularly wary of with pterygium surgery. "Pterygium may be a limbal stem cell abnormality to begin with," he said, adding that this is why the vessels grow onto the cornea. To avoid complications stem- ming from MMC, Dr. Rapuano rec- ommended keeping this away from the limbus, either just under the conjunctiva or just on the cornea away from the limbus. For pterygi- um surgery with MMC, he stressed the importance of always having conjunctiva covering the bare sclera. "If you're using mitomycin, I think that you have to have some sort of tissue, such as conjunctiva or amniotic membrane, to cover the bare sclera because there have been numerous reports of scleral melts," he said. This is especially true when the sclera is not covered with either conjunctiva or amniotic membrane. In addition to MMC applied by the practitioner, Dr. Lee noted that topical MMC drops can be used for patients with ocular surface squa- mous neoplasia. However, this is not usually his first choice. "I prefer using topical interferon alpha at 1 million parts per unit QID for several months," Dr. Lee said. "But if patients cannot afford the medicine, I will place lower punctal plugs and use topical mitomycin 0.02% QID for 1 week with 1 week off and then a second week of treatment at the same dose." The interferon alpha is easier on the eye, but can cost up to $1,000, whereas the MMC usually ranges from $75 to $200, he said. Use of MMC is contraindicated for those with corneal edema or those with severe dry eye, autoim- mune dry eye, and compromised corneal endothelium. In such patients, the MMC is too toxic for the surface of the cornea. "With dry eye patients, it can damage the stem cells," Dr. Lee said, adding that it can make dry eye worse and can cause corneal and scleral melts. For corneal edema patients, it is toxic to the corneal endothelium. Overall, Dr. Lee urged caution when using MMC in pterygium surgery. However, with other types of procedures, he said the chances for complications are much lower. "Long-term effects on the corneal endothelium are not known, but short-term corneal complications are minimal when using short applica- tion times and vigorous washing of the ocular surface after PRK or kera- tectomy cases," he concluded. EW Reference 1. Lindquist TP, et al. Mitomycin C-associated scleral stromalysis after pterygium surgery. Cornea. 2015;34:398–401. Editors' note: Drs. Lee and Rapuano have financial interests with Bio-Tissue (Doral, Florida). Contact information Lee: lee0003@aol.com Rapuano: cjrapuano@willseye.org He advised practitioners to be cautious that the concentration is not too great or applied for too long. "The big things that I see as a cornea specialist are overuse of MMC or using too high of a concentration, which does cause stem cell defi- ciency," he said. "That's one thing that we see with glaucoma patients because [the physician] has used it for 2 minutes, sometimes 3 minutes, and there can be superior stem cell deficiency from using it." Dr. Lee also stressed the impor- tance of ensuring that the concen- tration is accurate as this is usually

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