Eyeworld

I THERAPEUTIC REFRACTIVE CORNEAL SURGERY N FOCUS 70 | EYEWORLD | APRIL 2020 Contact Hardten: drhardten@mneye.com Rapuano: cjrapuano@willseye.org Schoenberg: evan.schoenberg@ gaeyepartners.com The most at-risk patients are those whose corneal disease comes from previous herpes viral infection or who have some sort of severe dry eye or limbal stem cell deficiency contrib- uting to their issues. "I don't consider these patients excluded from treatment, but they're higher risk and need to be counseled more care- fully about possible complications," he said. In extreme cases, these may be patients who are destined for a corneal transplant and the salvage attempt is PTK. Dr. Schoenberg shared a case of a patient he treated who previously had severe herpetic stromal keratitis. He got through the infection but ultimately was left with central stromal scar and substantial stromal thinning that was induc- ing a lot of irregular astigmatism. "We had him fitted in scleral contact lenses, which managed the astigmatism, but his vision was still very poor because of the dense stromal scar," Dr. Schoenberg said. "We discussed the risks of laser treatment, including that of viral reactivation." With pre- and post-treatment valacyclovir (1 gram three times daily starting a week before and continuing for a month after, then 1 gram daily for the next year), Dr. Schoenberg performed a transepithelial PTK via a myopic ablation, normalizing the shape of the cornea and removing much of the scar. This deliberately made him into a +9.00 hyperope, which took him from 20/200 best-corrected to +9.00 20/40. The second step was cataract surgery using a high-power IOL matched to the induced spherical aberration. This took him from +9.00 20/40 to +0.50 sphere for 20/40+. Dr. Schoenberg also highlighted the pos- sibility of corneal haze. When he performs a substantial ablation, he uses mitomycin-C (MMC) and a longer exposure than he would normally use in a routine refractive case. He uses MMC 0.02% for 30 seconds. He also does an extended steroid taper, typically prednisolone or loteprednol four times a day for a month. He will taper slowly in a 2-week increment, then use a low-potency steroid for a few months after the taper of the steroid. He also recom- mends that patients take vitamin C supplements for the first few months and use sunglasses when outdoors. Haze remains a risk with large treatments, but these measures tend to mini- mize that risk, he said. Perspectives of Evan Schoenberg, MD Dr. Schoenberg said PTK is a laser treatment that's intended to remove scars from or produce a smoother shape for the anterior cornea. On some laser platforms, PTK and PRK are the same laser procedure performed with different intentions, but other laser platforms have a dedicated PTK mode. "Either way, the target is clearing an anterior stromal opacity, resurfacing an irregular Bowman's membrane, or decreasing differences in stromal thickness," he said. PTK has more recently been supplement- ed by topography-guided PRK, but it's not replaced by it, Dr. Schoenberg said. There are some pathologies for which topography-guid- ed PRK is a great solution but others where it wouldn't be effective at all and PTK is a better approach. "Sometimes you need a sequential plan: PTK first to produce symmetric epitheli- um and less opacity, then topography-guided to provide focus," he said. The indications are varied, Dr. Schoenberg said, and they include previous corneal ulcer, previous trauma, or any other corneal pathology that induces topographic change or scarring. "The first thing I think about is whether we're looking at the visual axis directly, or if we are looking at the topographic effect of a peripheral or mid-peripheral change on the visual axis," he said. You want to know if you are trying to remove a scar that's blocking vision or trying to reshape the cornea to be a more effective shape for good vision. When it's a topographic irregularity, Dr. Schoenberg thinks a hard contact lens over refraction is the most important first assessment tool. If that is effective, you should discuss continuing with a specialty contact lens fitting versus the surgical laser solution, he said. If it's an opacity in the visual axis, a hard contact lens is less likely to be helpful. "The next most important diagnostic tools that I use, other than the slit lamp itself, are the topographer and anterior segment OCT," Dr. Schoenberg said. "Anterior segment OCT is such an important tool for assessing the cornea when considering whether PTK would be help- ful or not." Most modern OCT systems have an anterior segment module, even without a cornea upgrade. continued from page 69 About the doctors David Hardten, MD Minnesota Eye Consultants Minneapolis, Minnesota Christopher Rapuano, MD Wills Eye Hospital Philadelphia, Pennsylvania Evan Schoenberg, MD George Eye Partners Woodstock, Georgia Relevant disclosures Hardten: None Rapuano: None Schoenberg: None

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