EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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84 EW GLAUCOMA February 2011 February 2012 Glaucoma editor's corner of the world Glaucoma management in the DSEK patient by Faith A. Hayden EyeWorld Staff Writer W Descemet's stripping endothelial keratoplasty (DSEK) has been a break- through in the treatment of decreased vision from corneal opacities. It has become a wonderful alternative to penetrating keratoplasty (PK) for patients with endothelial dysfunction. The coincidence of glaucoma and corneal disease is frustratingly com- mon, and the use of DSEK in glaucoma patients is the subject of this month's Glaucoma corner of the world. We are fortunate to have two experts, Richard Lehrer, M.D., and Ramesh Ayyala, M.D., who are glaucoma specialists with vast experience in DSEK. They review the many challenges of perform- ing DSEK in glaucoma patients. Most of these DSEK problems stem from glau- coma surgery—whether it's hypotony or the presence of a drainage tube or shunt. These challenges demonstrate the need for more minimally invasive techniques for glaucoma surgery that would be more compatible with ad- vances like DSEK. For example, it will be much less technically demanding to perform DSEK in a glaucoma eye with an iStent (Glaukos, Laguna Hills, Calif.), CyPass (Transcend Medical, Menlo Park, Calif.), or Hydrus (Ivantis, Irvine, Calif.) than in an eye with the large and prominent tubes associated with exter- nal drainage devices. Furthermore, we are anticipating that these minimally invasive glaucoma procedures will be safer and hopefully reduce the number of glaucoma patients developing corneal complications and ultimately needing DSEK. But until then, DSEK can restore vision more efficiently and safely than a PK for glaucoma patients with a corneal opacity. Reay Brown, M.D., glaucoma editor hen glaucoma and corneal disease co- exist, they may create a perfect storm of impending complica- tions and surgical challenges. Although not common, these are extremely complicated patients that need specialized, individualized care. There are a number of circum- stances that can occur causing corneal decompensation in glau- coma patients such as implanted drainage devices, acute or chronic exposure to elevated IOP, and pre- existing Fuchs' dystrophy. "Any time a patient has intraoc- ular surgery, it can exacerbate the Fuchs' dystrophy," said Richard Lehrer, M.D., an Ohio-based glau- coma specialist. "If the patient has had cataract surgery, glaucoma sur- gery, or multiple glaucoma surgeries, this can certainly make things worse." Corneal decompensation is one of the main complications of glau- coma drainage device surgery, said Ramesh S. Ayyala, M.D., professor of ophthalmology, Tulane University School of Medicine, New Orleans, and has been reported in up to 30% of patients with long-term follow- up. "Graft failure from decompensa- tion or rejection in patients with penetrating keratoplasty and glau- coma following glaucoma drainage device surgery has been reported in the range of 10-51% (an average of 36.2%)," he said. "The etiology of corneal decompensation and graft failure is probably multifactorial." Factors include previous surger- ies, inflammation, elevated IOP lead- ing to endothelial cell loss, and the state of the endothelial cells prior to glaucoma drainage device surgery. "If the endothelial cell health is compromised prior to surgery, for any reason, the post-operative corneal decompensation is just a re- flection of the natural course of the disease state versus the glaucoma drainage device implantation com- promising the endothelial status," said Dr. Ayyala. There are a couple of contraindi- cations to a Descemet's stripping en- dothelial keratoplasty (DSEK) in these patients, said Dr. Ayyala. For example, if a patient has hypotony from overfiltration, that has to be corrected first. Patients with a stro- mal scar rather than endothelial dys- function will need a penetrating keratoplasty instead of a DSEK. The presence of tube shunts, trabeculec- tomy, or an EX-PRESS shunt (Alcon, Fort Worth, Texas) are not con- traindications, said Dr. Lehrer, but these things "may make [a DSEK] more difficult." For example, "I had a patient who had a Baerveldt shunt [Abbott Medical Optics, Santa Ana, Calif.], and I had to tie off his tube for a couple of days in order to allow his graft to adhere to the air bubble," he said. There are many challenges that can arise before and during a DSEK, including hypotony and patients with long tubes or tubes touching the cornea, said Dr. Ayyala. They may need repositioning prior to DSEK. It can also be difficult to get an air fill in the eye during the DSEK. "The air will seek the easiest es- cape route," Dr. Lehrer explained. "If you have a very well-functioning tube shunt or trabeculectomy, the air will disappear into the tube or into the bleb and you can end up filling quite a bit of air into the eye. It can make the surgery a lot more difficult." In fact, air escaping through a tube may cause graft dislocation rates to be higher, said Dr. Ayyala. "In our series, we observed a graft dislocation rate of 38.9% is comparable to the higher end of the 3-35% dislocation rate described in the literature in non-glaucoma pa- tients," he said. "These findings may be consistent with the frequently de- scribed phenomenon of a glaucoma drainage device predisposing to leak- age of the floatation air bubble or rubbing of the drainage device tube on the graft leading to an increased propensity for graft dislocation. This higher rate of dislocation occurred mostly in the first few patients where only air was injected into the AC [anterior chamber] under the graft." The induction of the "air lock" technique, which allows for an in- jection of balanced salt solution first into the anterior chamber followed by a rapid injection of 3 ccs of air, dramatically decreased the rate of dislocation by forcing the balanced salt solution into the bleb or tube, A patient 1 day status post-DSEK with EX-PRESS shunt showing air in bleb The typical appearance of a patient 3 months after DSEK Source: Richard Lehrer, M.D.