Eyeworld

EW GLAUCOMA 90 March 2018 Research highlight by Maxine Lipner EyeWorld Senior Contributing Writer Investigators found that the re- sults were in line with their anecdot- al experience. While glaucoma still remains a serious complication after corneal transplantation, their think- ing that this was not as great with newer transplant techniques was confirmed. "With the newer style transplants that we do, specifically the endothelial keratoplasties and lamellar keratoplasties, the risks of exacerbation of raised IOP or wors- ening glaucoma are greatly reduced in these cases," Dr. Chew said. To stave off glaucoma with endothelial keratoplasties, there are several techniques that are typically used. "For endothelial keratoplas- ties, many physicians recommend doing a prophylactic laser iridotomy or intraoperative surgical iridectomy to minimize the risks of pupillary block and raised IOP after surgery," Dr. Chew said, adding that this sometimes occurs secondary to the gas bubble or air bubble that is in- jected into the anterior chamber. Dr. Chew emphasized the need for close monitoring of patients. "We have to continue to follow our patients closely after surgery to ensure that there's no pupil block glaucoma and to monitor for steroid response." In cases of steroid response, patients can possibly be given a milder agent or placed on an anti-glaucoma medication. Also, steroids can be tapered more quickly in the newer lamellar keratoplasties compared to the traditional PKPs, further reducing the risk of in- creased IOP. Considering prosthetic transplants Also, as part of the study, investiga- tors considered the occurrence of glaucoma in conjunction with the Boston KPro artificial cornea and the osteo-odonto-keratoprosthesis. "There's little data on these cases be- cause they're not as prevalent," Dr. Chew said. Because it is difficult to measure the IOP accurately due to the structure of the anterior segment in cases where a prosthetic cornea or an osteo-odonto-keratoprosthesis is placed, it may be necessary to use other strategies for measuring IOP or observing the optic nerve head. In addition, perioperative glau- coma treatment, including using Considering how patients are faring with evolving transplant techniques G laucoma occurrence with traditional corneal transplants ranges from 5.5% to 47.9%, with real world estimates being around 20% to 30%, according to Hall Chew, MD, associate professor of ophthalmology, University of Toronto. But how frequently does this complication occur with newer forms of corneal transplantation such as the lamellar keratoplasties? A study published in Survey of Oph- thalmology examined how glaucoma may be affecting such cases. 1 The impetus to consider what might be going on with glaucoma grew out of the newfound popular- ity of such procedures. "There has been a large shift from the tradition- al full thickness corneal transplant (PKP) to the specialized endothelial keratoplasties as well as the anterior lamellar keratoplasties," Dr. Chew said. While anterior lamellar kerato- plasties are not catching on quite as quickly, if you look at the numbers of endothelial keratoplasties, these are outpacing the full thickness transplants, he noted. "For many reasons, it's better for the patient, both in the visual results and how quickly we can rehabilitate patients with endothelial keratoplasties com- pared to traditional PKPs," Dr. Chew said. These also tend to be safer for patient in that the risk of rejection is lower, steroids can be tapered and discontinued over a shorter duration, and the risk of traumatic wound dehiscence is negligible com- pared to traditional PKPs. Delving into the literature Spurred by personal experience that seemed to indicate that glaucoma is less prevalent in endothelial keratoplasties than with traditional transplant approaches, Dr. Chew set out to see if the literature supported this. "We did a literature search up to the present date searching for cor- neal transplantation and glaucoma, glaucoma surgery and the various types of transplants that are being done," Dr. Chew said. "Then we in- corporated each of the articles into our review." Glaucoma on the corneal replacement cusp Postoperative day 7 for perforation secondary to recurrent herpes simplex stromal keratouveitis and uveitic glaucoma Postoperative day 28 with central clear cornea and peripheral corneal haze Slit beam confirming DMEK attachment and complete anatomic replacement of Descemet's membrane and endothelium Source: Hall Chew, MD continued on page 92

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