Eyeworld

SPRING 2024 | EYEWORLD | 87 C rest of stem cells, and for years he managed just fine with that." Dr. Jeng said scleral lenses are usually his first go-to if there is some degree of stem cell is- sue, though this may not work for every patient. By understanding the pathophysiology of limbal stem cell dysfunction or deficiency, Dr. Jeng said that doing a penetrating keratoplasty (PK) or any sort of keratoplasty does not fix the problem because the problem is the stem cells, not the cornea itself. "If it's an isolated stem cell issue, then keratoplasty doesn't have a role." So, if scleral lenses don't work, you're left with really two options, Dr. Jeng said. One is a keratoprosthesis, and the other is a stem cell transplant. Dr. Jeng has used keratoprosthesis for stem cell deficiency. "You have to be very careful about who you choose because, even though it's an indication for doing the procedure, they have to still be able to epithelialize," he said. "If they can't, doing a KPro, you're asking for trouble. If it can't epithelialize up to the optic, then you can't do it because they'll melt and have a bad outcome." For this reason, Dr. Jeng is very con- servative when choosing a KPro to treat patients with limbal stem cell deficiency and said he wouldn't generally recommend this option. That leaves stem cell transplantation, of which there ae several options. One is trans- planting from one eye to the other. In the case of a unilateral chemical burn, for example, you could do that, Dr. Jeng said. If the unaffected eye is completely unaffected, then you can take either four small clock hour blocks from the other eye and move to the diseased eye or you could do simple limbal epithelial transplant (SLET). "While I personally haven't had success with [SLET], others definitely have," he said. The second option is a living, related donor, which is very similar to using cells from a cadav- eric donor. Use of cadaveric donors, described by Edward Holland, MD, and his group, requires systemic immunosuppression for a year, Dr. Jeng said. "I think that a lot of ophthalmologists are uncomfortable with that, and if you don't do it right, you either have a failure of surgery or you could make the patient very sick. He added that ophthalmologists alone should not be managing these transplant medications. These are at the level of a kidney or heart transplant, he said, so you need to have the infrastructure with a transplant team that's in place. He noted that Dr. Holland's Cincinnati Protocol has this infra- structure. "I've had a few patients ask about that [option], and we have sent them to Cincinnati to do it because we don't have an infrastructure set up for it," Dr. Jeng said, adding that one other obstacle is that he really doesn't see the surgical volume necessary to set up a program like this. Dr. Jeng said that he has personally used this technique. "But I felt that I didn't do a high enough volume that makes me the best person to do this," he said. "It makes sense, but we need to make sure any center set up has the appropriate volume to serve the patients." In terms of surgeons being trained to treat limbal stem cell deficiency or dysfunction, Dr. Jeng said he believes new fellows are well versed in when someone needs a scleral lens, and they're probably trained in KPros, as well. They are most likely not trained in stem cell transplants because many centers don't do them, he said, emphasizing that the surgery itself is not the difficult thing, but it's managing the patients postoperatively. Sophie Deng, MD, PhD Dr. Deng sees patients for limbal stem cell deficiency very frequently in her practice. "We have established a center for limbal stem cell deficiency (LSCD), so we get referrals from the region and sometimes from across the country," she said, adding that she often sees several of these cases per week. She said the first step, even before treat- ment, is to stage the disease. She uses live imaging to evaluate the stem cell function in these eyes. "We do anterior segment OCT first to look at the epithelial thickness in these eyes to make sure we don't misdiagnosis the stem cell deficiency," she said. "Subsequently, we will perform in vivo confocal microscopy on these eyes to look at the microstructure of limbus and cornea." We come up with a formula to quantify the stem cell function, she said. continued on page 88

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