EyeWorld Asia-Pacific June 2020 Issue

EWAP JUNE 2020 39 CORNEA may need a corneal transplant. If there is severe irregularity or farsightedness, the patient may need a hard contact lens. Dr. Rapuano added that insurance coverage may be an issue with PTK. If a physician is doing PTK at a commercial laser center that doesn’t do commercial billing, the patient may have to pay cash for the procedure. Perspectives of David Hardten, MD Dr. Hardten said that the most common reason he uses PTK is for epithelial basement membrane dystrophy (EBMD), vœÀ iˆÌ…iÀ ۈÃÕ>Þ È}˜ˆwV>˜Ì irregular astigmatism that EBMD causes or associated recurrent erosions. Other treatment œ«Ìˆœ˜Ã ˆ˜VÕ`i ÃÕ«iÀwVˆ> keratectomy or stromal puncture, but the challenge in these alternatives is you typically don’t get all of the basement membrane dystrophy. “With PTK, you can typically resolve the pathology over a broader area,” Dr. Hardten said. */ ˆ˜ «>̈i˜Ìà ܈̅È}˜ˆwV>˜Ì EBMD deposits with blurry vision can be used to polish deposits off, he said. Dr. Hardten said PTK can also be useful for treating Salzmann’s nodules. Part of the procedure is the laser component, but it is important to do a careful ÃÕ«iÀwVˆ> ŽiÀ>ÌiV̜“Þ wÀÃÌ° Dr. Hardten will use the laser to w˜i Ì՘i ̅i «œˆÃ…>vÌiÀ `œˆ˜} ̅i ÃÕ«iÀwVˆ> ŽiÀ>ÌiV̜“Þ and debridement of the larger components. À° >À`Ìi˜ Ã>ˆ` ̅>Ì ˆÌ½Ã `ˆvwVÕÌ when the pathology is very deep. If the pathology is going to require removing cornea more ̅>˜ Çx ù“ `ii«] ˆÌ½Ã V…>i˜}ˆ˜} to take the non-involved cornea down enough in order to regularize the corneal curvature. In patients who have other underlying problems, like neurotrophic keratitis, zoster, or problems where they’ll have `ˆvwVՏÌÞ ÜˆÌ…i«ˆÌ…iˆ>…i>ˆ˜}] there is another set of issues that you’ll have to deal with, Dr. Hardten said. It’s often a big challenge, not from the ability to improve the scar with the laser, but what caused the original scar will also potentially cause you trouble during the healing period of the PTK. 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 supplemented by topography- guided PRK, but it’s not replaced by it, Dr. Schoenberg said. There are some pathologies for which topography-guided 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: */ wÀÃÌ Ìœ «Àœ`ÕVi Ãޓ“iÌÀˆV epithelium 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. º/…i wÀÃÌ Ì…ˆ˜} ̅ˆ˜Ž >LœÕÌ 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 wÀÃÌ >ÃÃiÃÓi˜Ì ̜œ° v ̅>Ì ˆÃ effective, you should discuss continuing with a specialty Vœ˜Ì>VÌ i˜Ã wÌ̈˜} ÛiÀÃÕà ̅i 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 helpful or not.” Most modern OCT systems have an anterior segment module, even without a cornea upgrade. 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 Vi `iwVˆi˜VÞ Vœ˜ÌÀˆLṎ˜} ̜ their issues. “I don’t consider these patients excluded from treatment, but they’re higher risk and need to be counseled more carefully 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 inducing a lot of irregular astigmatism. º7i…>`…ˆ“ wÌÌi` ˆ˜ ÃViÀ> 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