Eyeworld

43 EW FEATURE February 2019 • Facing complicated glaucoma cases be detrimental to the survival of the corneal graft. "GDD controls IOP but increases the risk of graft rejection by 30–50%. Cyclo-destruc- tive procedures have unpredictable IOP results with an increased risk of graft rejection. This applies also to micropulse, which in our experience in these complex cases has been less than POAG patients with regard to IOP control. 5 MIGS might work, but once you enter the anterior chamber, graft rejection is a risk. Trab or trab-like procedures are good for graft survival and IOP control but contraindicated (relative) in the presence of contact lens use secondary to the risk of infection. Finally, canaloplasty ab externo with 10.0 Prolene is for me the best procedure both for IOP control and graft survival, with no concerns for contact lens related issues, as there is no bleb. I have a series of patients in this category over the years with long-term success, and it is my preferred method in patients with PKPG," Dr. Ayyala said. When it comes to combining these surgeries, experience counts. Dr. Berdahl thinks that endothelial/ corneal replacement procedures and glaucoma surgery can be combined, however, with caution. "I have done a number of iStents [Glaukos, San Clemente, California] at the same time as DMEK. However, you need to realize that there can be reflux and heme, and that can make doing a DMEK very difficult," he explained. "The more conservative play is a DSEK. We have presented our data showing that it can be done successfully. 6 One of the things I like about the combined approach is that I am less worried about ste- roid-induced IOP spikes when there is a trabecular bypass stent. I would suggest using the procedure that is least likely to induce hyphema. If you're doing it in combination with a cataract surgery, I would suggest doing the glaucoma procedure prior to removing the cataract so that the heme can be washed away and bleeding likely stopped by the time the endothelial transplant occurs." The study, for which he was a co-investigator, involved combining DMEK or DSEK with a trabecular mi- cro-bypass stent replacement, along with cataract surgery in 15 patients with Fuchs' endothelial dystrophy, EyeWorld. "If these devices come into contact with the corneal endo- thelium, it will lead to a decreased endothelial cell count. We also know that low intraocular pressures alone, hypotony, can cause a loss of endo- thelial cells. I think we have to be extra diligent in making sure devices are not in contact, or in too close proximity, to the corneal endothe- lium. We also need to ensure that the surgeries that we are doing are at a very low likelihood of creating hypotony." Combining surgeries Ophthalmic surgeons always need to take the altered endothelium into account in patients with glauco- ma or with a history of glaucoma surgery. Often individuals will require both glaucoma surgery and partial or full thickness keratoplasty. According to Dr. Berdahl, the biggest challenge in these eyes is how the anterior chamber will behave during surgery. "The anterior chamber is the challenge. You have to retain the air bubble long enough to ensure at- taching the graft," he said. "I gener- ally put some viscoelastic in the lu- men of the tube shunt or the ostium of the trabeculectomy in an effort to keep air in the anterior chamber and not going into the bleb. This is only modestly successful, so I do think that endothelial transplants are more challenging in these eyes. Some surgeons advocate for DSEK only, although there is literature to support that DMEK does just as well in these scenarios. I generally make a judgment call on how the eye is going to behave, and if I think it is going to be more difficult, then I do a DSEK," Dr. Berdahl said. In Dr. Ayyala's extensive experi- ence with penetrating keratoplasty and glaucoma over many years that includes a number of publi- cations, what a successful surgery comes down to is eye pressure and the donor corneal graft. "I had the opportunity to operate on a lot of penetrating keratoplasty glaucoma (PKPG) cases over the past 20 years. There are two main things to con- sider in these cases; the first is IOP control and the second is saving the graft. One at the exclusion of the other is not good for the patient," 4 he said. According to Dr. Ayyala, most glaucoma surgeries are going to Figure 4. Additional viscoelastic is used to create space above and below the stent and to protect the cornea during removal. Figure 5. Large MST scissors are then used to trim the stent. The angle of approach is very important in order to avoid trauma to the cornea and iris and to avoid moving the stent to the side and creating a cyclodialysis cleft. In this case the wound needed to be enlarged slightly to provide an optimal angle. Figure 6. MST graspers are then used to remove the stent. Figure 7. On gonio you can see the stent is flush with the angle and away from the cornea. Source (all): John Berdahl, MD continued on page 44

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