Eyeworld

I THERAPEUTIC REFRACTIVE CORNEAL SURGERY N FOCUS 68 | EYEWORLD | APRIL 2020 by Ellen Stodola Editorial Co-Director P TK can be used for various types of corneal pathologies. Depending on the type of opacity and depth in the cornea, other treatments may also be needed. Experts discussed how they use PTK and the conditions for which they employ it. Perspectives of Christopher Rapuano, MD According to Dr. Rapuano, PTK was FDA approved in 1995 for treating corneal pathology. It's good for treating several types of patholo- gy, he said. One type is elevated opacities, like Salzmann's nodules, keratoconus nodules, and elevated scars. "Some of those diagnoses don't need PTK, but some of these opacities don't come off well with superficial keratectomy, and you have PTK as backup," Dr. Rapuano said. For those, Dr. Rapuano will bring the pa- tient to the laser and do superficial keratectomy with a blade under the laser microscope. He said he usually gets a pretty smooth surface and will do a little PTK smoothing after that. "But sometimes it's not very smooth after I've done a mechanical lamellar keratectomy, then I have the laser." PTK offers a real advantage, he said, when you're handling anterior stromal opacities or those in the front 15–20% of the cornea. Patients with superficial scars and many types of anterior and stromal corneal dystrophies can be treated. Most patients with granular corneal dystrophy, some patients with lattice corneal dystrophy, and occasional patients with macular corneal dystrophy can benefit from PTK. One of the pearls Dr. Rapuano gives when teaching about PTK is if it's an anterior opacity and if most of the opacity is in the top 15–20% of the cornea, this could be a good candidate. But if it's much deeper than that, the patient is probably not a good candidate. A lot of dystrophy patients have 80% of the opacity in the top 10% of the cornea and the other 20% is deep in the cornea, Dr. Rapua- no said. When some physicians do PTK they think they have to get all the opacity out, and they take off a lot of the cornea. "That does PTK for corneal pathology At a glance • PTK may work best if most of the opacity is in the anterior of the cornea. Even getting most of the opacity can benefit the patient's vision. • PTK can be difficult when the pathology is very deep. If there is pathology more than 75–100 µm deep (depending on the corneal thickness, especially where it is most thinned), it can be challenging. • Haze could be a possible concern following ablation procedures. Mitomycin-C may help, along with other considerations. EBMD Move reticle toward the limbus and treat the outer cor- nea, trying to get 4–6 µm to all areas for the cornea. Source (all): David Hardten, MD Start with central laser (4–6 µm) For this issue of EyeWorld, we asked world leaders in therapeu- tic corneal refractive surgery to share their wisdom. This section is packed with pearls on how to treat various corneal issues. It wasn't that long ago that none of these procedures were available to patients with surgical corneal needs. Please join me in thanking these doctors and the writers at EyeWorld for their hard work. I hope you enjoy this important issue focusing on the pathology side of refractive corneal surgery. — Vance Thompson, MD Refractive Editor

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