EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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E W GLAUCOMA 72 by Maxine Lipner EyeWorld Senior Contributing Writer Combination platter on the menu Dishing out refractive results of combined cataract and glaucoma surgery F or many, the idea of per- forming combined cataract and glaucoma surgery is an attractive option. But are r efractive results with com- bined surgery as good as they might be otherwise? That's what investiga- tors set out to discover in a recent study published in the November 2013 issue of the Journal of Glau- coma, according to Jonathan H. Tzu, MD, retina fellow, Bascom Palmer Eye Institute, University of Miami. In considering this, they found that as much as 74% of patients attained refractive success with combined surgery, he said. Performing combined surgery is fairly common these days, Dr. Tzu finds, particularly for those who are not well controlled on drops alone and who have a visually significant cataract. Fellow investigator Sarah R. Wellik, MD, associate professor of ophthalmology, Bascom Palmer Eye Institute, agreed that the need for this arises frequently. "When you have a patient with glaucoma and cataract, probably half the time the patient is going to be eligible for a combined surgery," she said. Considering refractive outcomes The investigators set out to deter- mine how refractive outcomes with the combined procedure compared with those who underwent cataract surgery alone. "When you do these procedures you want to have good refractive outcomes as well as the glaucoma well controlled," Dr. Tzu said, adding, "We wanted to see what kind of refractive changes we would expect in someone who had both procedures done at the same time." Glaucoma surgery alone is known to do things like induce astigmatism, change the axial length, and change the anterior chamber depth, he said, adding all of these things can affect the final refractive outcome. "It's important for most people to determine whether or not they'll need glasses afterward, so it was important for us to know what we're getting when we do these procedures combined versus separately," he said. Dr. Wellik explained that inves- tigators wanted to consider both tra- beculectomy and glaucoma drainage devices in combination with cataract surgery because this had not been delved into very much before. "There are a lot of studies on cataract surgery and trabeculectomy, but not very much information out there with glaucoma drainage de- vices," she said. "We wanted to see if there were any differences with the two kinds of major glaucoma surgery combined with cataract surgery." Included in the retrospective case series, Dr. Tzu reported, were patients who had undergone simul- taneous cataract extraction with ei- ther trabeculectomy or implantation of glaucoma drainage devices at Miami Veteran's Affairs Medical Center. Investigators reviewed their charts, as well as those of age- matched controls who underwent cataract surgery alone. They found that 32 of 43 eyes undergoing combined procedures attained successful refractive results, with success defined as a spherical equivalent between –1 D and +0.5 D, Dr. Tzu noted. However, patients in the combined group postopera- tively had more astigmatism, with a mean of 1.31 D compared with 0.99 D in the control group. Both tra- beculectomy and glaucoma drainage devices have the potential to induce astigmatism, he observed. "With a trab you're creating a scleral tunnel right there, either superiorly or su- pertemporally, and with a tube you're still manipulating a lot of the peripheral cornea, more so than you would with cataract surgery alone," he said. "You're doing things to the eye that would induce a lot more astigmatism." Such induction of astigmatism was a concern going into the study. "We didn't know what kind of astig- matism outcomes there were going to be from glaucoma drainage de- vices because there are also sutures in the upper quadrant of the eye, and we thought that could cause some astigmatism, but it turned out that it didn't cause very much," Dr. Wellik said. Dr. Tzu agreed that there was a bit more cylindrical change but that overall refractive outcomes were still very good. While refractive outcomes for combined procedures were good, this did not apply to older patients, in general, Dr. Wellik observed. "That was surprising," she said, adding, "It could be we have a more difficult time refracting older folks and also possibly that comorbidities are greater—because they're older their glaucoma may be worse." She also pointed out that there wasn't a major difference between those who underwent trabeculec- tomy and those who had the February 2011 February 2014 A chieving an excellent refractive outcome is the goal of every c ataract surgery—even cataract surgery combined with a trabeculectomy or tube shunt. We expect the challenge to be greater with combined surgery, and that is why this month's "Glaucoma editor's corner of the world" on refractive outcomes is so important. We are fortunate to have the insights of Jonathan Tzu, MD, and Sarah Wellik, MD, from their study of the refrac- t ive results of combined surgery. The potential problems of cataract surgery combined with a tube or trab are daunting. Both glaucoma operations require conjunctival incisions, scleral incisions, suturing and cautery—all of which can induce astigmatism. The goal of the opera- tions is to lower the intraocular pressure— which can exacerbate astigmatism. Meanwhile, most patients undergoing these procedures have already developed visual field loss and that can limit visual recovery as well. Many cataract/glaucoma surgeons love combined surgery. The chance to both improve vision and control pressure with a single operation is very appealing. However, other surgeons are not so tempted. My own approach is to avoid combined surgery because of these challenges and to perform a cataract surgery by itself wherever possi- ble. The emergence of MIGS procedures has made it increasingly possible to achieve refractive success and a lower pressure with a low-risk combined surgery. Since the MIGS procedures can be done without a separate incision, the chance of inducing additional astigmatism is low and the refractive results can approach those of cataract surgery alone. Whether or not you seek out opportu- nities to combine cataract surgery with a trab or tube, there will be clinical situations where combined surgery is the best option. It is reassuring to learn from Drs. Tzu and Wellik that even these adverse glaucoma cases are still compatible with refractive success. Reay Brown, MD, glaucoma editor In a pseudophakic patient such as this one, who also underwent trabeculectomy and tube placement, there was the potential to induce astigmatism. However, study results show that not all that much resulted. Source: Bascom Palmer ophthalmic photographers Rosa Long and Marlene Reda Glaucoma editor's corner of the world 72-77 Glaucoma_EW February 2014-DL2_Layout 1 1/30/14 10:55 AM Page 72