Eyeworld

EW FEATURE 95 With the cataract portion of the procedure, Dr. Price stressed that it's important to use a cohesive rather than a dispersive viscoelastic. "The reason is once you remove the cataract, you want to strip De- scemet's in the central part of the cornea and put your DSEK graft up," Dr. Price said. "If there's a dispersive viscoelastic then it's difficult to en- sure that you've gotten all of the vis- coelastic out." Determining the correct IOL power to use can also be tricky. "There are series that have been re- ported that show hyperopic shifts after DSEK of anywhere from .5 D to 2 D," Dr. Price said. He finds that some of the hyperopic shift is de- pendent on how thick the donor tis- sue is and on the shape or contour of the button. "Just like everyone is a different height and weight, corneas come in different shapes and contours," he said. "When you cut with a microkeratome, you may have some that have more of a meniscus shape and others that are more planar." For those that are more meniscus-shaped and thicker on the edge, this may ultimately re- sult in a greater hyperopic shift. To help overcome problems with hyperopic shift, Dr. Holland recommended developing a nomo- gram of sorts. "Surgeons should look at their results, but typically the EK procedure causes a hyperopic shift," he said. "The fudge factor is some- where in the range of –.75 to 1.50 D that you would put into your pre- operative calculation—for us it's be- tween 1 D and 1.25 D." Prized outcomes It is the DSEK portion of the combi- nation procedure that ultimately tends to be the limiting factor for outcomes. To get the best outcomes with the combination technique, Dr. Holland recommended using the thinnest tissue with a process he terms "thin EK." He defined those patients as ones who receive eye bank tissue of 130 microns or less. The thin EK technique evolved over the last few years. In almost all cases, eye banks precut tissue. "It used to be that the average thickness that the surgeon requested was somewhere between 160 and 180 microns," Dr. Holland said. "We started noticing a few years ago that with the thinner EK tissue, the pa- tients saw better." With the thin EK technique, outcomes have proven to be better for Dr. Holland. In an arti- cle that appeared in the October 2010 issue of Cornea, Dr. Holland and fellow investigators reported that patients who received the thin EK tissue showed a statistically sig- nificant improvement in BSCVA. "We found that 100% of thin EK eyes were 20/25 and 71% were 20/20," he said. "With the standard EK eyes with tissue over 130 mi- crons, only 50% were 20/25 and 19% were 20/20." Dr. Francis Price likewise favors the use of thin tissue. He dubs his thin approach Descemet's mem- brane endothelial keratoplasty (DMEK). "For most patients after DSEK, the average vision is 20/30 to 20/40 best corrected, whereas after DMEK most patients are 20/20 to 20/25 and they have better vision," Dr. Price said. He acknowledged that there are some downsides since patients need more reinjections of air to push the thin stem donor tissue up in the first 2-3 weeks after surgery. But ulti- mately they do attain better vision with the thin approach. While Dr. Price does perform combined phaco/DMEK surgery, in some cases he prefers to do the pro- cedures in stages. "We do some of these as combined cases, especially if the patient came from far away or has a very dense cataract with a bad cornea," he said. "However, for a lot of these we're shifting to doing the cataract 1 month ahead of time." He finds that it's easier to constrict the pupil during the unfolding of the DMEK graft. "If you do a cataract at the same time, even if you use con- stricting agents like miochol or mio- stat, the pupil doesn't go down as small as it does if you have not done a cataract," he said. Going forward, Dr. Price sees the use of thinner tissues as becoming more of the norm with the combi- nation approach. "What I think is going to happen is that we're going to go to thinner and thinner grafts," he said. "As we've done more data analysis with the 1-year results, we're doing a lot more DMEKs, where it's just Descemet's and en- dothelium." Given the improved outcomes, Dr. Price thinks that the next big push will likely be working on predictabiltiy. "Our next big area of interest is to figure out if we can predict pre-operatively in the DMEK patients how much of a hyperopic shift they are going to get so that we can have more accurate IOL calcula- tions," he said. "What we find will determine whether or not we want to do the cataract before or after the DMEK surgery. As we can give peo- ple better vision, there may be an ability to give them premium IOLs, which we don't do now." Meanwhile, Dr. Holland thinks that the improved results will lead to earlier intervention. "Five or 6 years ago when DSEK started to become popular we would put off patients," he said. "As we got better results, we've become more aggressive, and we are certainly operating earlier in the Fuchs' part of the story." He pointed to the patient with 20/25 to 20/30 vision who was experiencing glare and haze and difficulty driving at night. "We would now consider a phaco DSEK, whereas 5 years ago we wouldn't do that," Dr. Holland said. "We're getting better results, so we can recommend surgery earlier for these patients." EW Editors' note: The physicians inter- viewed have no financial interests related to their comments. Contact information Holland: 859-331-9000, eholland@holvision.com Francis Price: 317-844-5530, wendymickler@pricevisiongroup.net Marianne Price: 317-814-2823, mprice@cornea.org DSEK lenticule is shown folded in preparation for insertion Source: Jonathan B. Rubenstein, M.D. March 2011 COMBINED SURGERY

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