EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/76185
February 2011 July 2012 EW REFRACTIVE SURGERY 33 8 pointers for better toric IOL surgery by Vanessa Caceres EyeWorld Contributing Editor Pre-op to post-op considerations W ith the right measure- ments and planning, a toric IOL can make a big visual difference for certain patients. However, there's also room for error if you're not careful. A few surgeons shared pearls to master the science and art of toric IOL implantation. 1. Eliminate pre-op misread- ings due to dry eye or blepharitis, said William Trattler, M.D., Miami. These conditions can alter a patient's refraction and corneal astigmatism, leading to inaccurate measurements as you decide which toric IOL to use. "If you don't have the right data going in, you'll never get your target," he said. When a patient has dry eye or blepharitis a few weeks before surgery, Dr. Trattler will treat the patient for at least a week pre-op. If the condition is improving when he sees the patient a week later, he'll go ahead and pro- ceed with the surgery on schedule. If the eye needs more time to heal, he'll delay surgery. 2. Consider corneal astigma- tism more than refraction, Dr. Trattler said. "We don't care initially about the refraction. We need the corneal astigmatism to find the astigmatic power," he said. That number may not always match the astigmatism in the patient's glasses as the lenses themselves add a certain degree of astigmatism, said Stephen S. Lane, M.D., adjunct clinical professor, University of Minnesota, Minneapolis. "Just because patients may have 2 diopters of astigmatism in their glasses doesn't mean they'll need a lens of 2 diopters to correct for astig- matism," he said. "You may find that patient has no astigmatism, or he may have more than what you were anticipating." Faster continued from page 32 increased patient satisfaction and more predictable outcomes, and it becomes obvious that speed does matter. EW Editors' note: Dr. Yoo is professor of ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami. Dr. Yoo has financial interests with Alcon, AMO, and Carl Zeiss Meditec. Contact information Yoo: 305-326-6322, syoo@med.miami.edu the steepest merid- ian of the cornea," he said. 4. Aim to keep Image of a patient with forme fruste keratoconus and regular astigmatism. This patient is an appropriate candidate for a toric IOL. There is 2.88 D of astigmatism Source: William Trattler, M.D. 3. Use the best in-your-hands tools to measure astigmatism, Dr. Lane suggested. Some surgeons will use the IOLMaster (Carl Zeiss Meditec, Dublin, Calif.) or the Lenstar (Haag Streit, Mason, Ohio); others will use manual keratometry or automated keratometry while others still will use corneal topogra- phy. "All can be accurate, but all measure things a little differently. You usually go by your experience and what's most accurate in your hands," Dr. Lane said. He prefers manual or automated keratometry as well as some topography. The same principle applies when you decide how you will mark the eye prior to surgery. Although various surgeons use different ap- proaches, Paul H. Ernest, M.D., Lansing, Mich., likes the marking system from Mastel (Rapid City, S.D.). "It has a level and marks at 3 and 9. In the OR, it has a two- handed technique and a 360-degree protractor that I hold in the non- dominant hand like an inverted wingnut, and I'll mark the axis of your surgically induced astigma- tism (SIA) and standard devia- tions as low as possible, Dr. Ernest advised. If you don't know what your averages are for those areas, find out, he said. His SIA is 0.25 D, and his standard devia- tion is 0.14. Dr. Ernest attributes those numbers to his incisions that are more posterior in direction, which he says he makes for better healing. "As a result, I'm not inducing very much astigma- tism in my incision," he said. 5. Remove as much viscoelas- tic material as you can before checking the lens positioning, Dr. Lane said. Otherwise, the material could cause the lens to rotate. "Make sure the viscoelastic material is re- moved behind the implant because the lens can slip and slide. Then remove all viscoelastic even behind the lens before you do the final positioning," he said. 6. Do what you can to prevent misalignment and lens rotation, Dr. Lane recommended. Although it is indeed possible to fix misalign- ment, it's better not to have to treat it in the first place. One way to pre- vent such a problem is with the use of new technology such as the WaveTec ORA (Aliso Viejo, Calif.), which takes intraoperative wave- front aberrometry readings, Dr. Lane said. If misalignment does occur, try to pinpoint the cause. "There's sur- geon-induced error because either you didn't mark the eye or you did mark it and failed to get the lens placed in it accurately. That's differ- ent than misalignment with the lens moving, where you had the lens in the right place and it moved after surgery," he said. One trick to prop- erly align the lens in this situation involves the following: "You can prolapse the optic out of the back and capture it anteriorly to prevent rotating. Sometimes you can use a capsular tension ring, such as the Henderson ring [Morcher, Stuttgart, Germany], to help stretch the cap- sule. The haptics get caught up and prevent it from rotating," he said. In terms of timing, if there's only a small amount of misalign- ment and it does not have a major effect on a patient's vision, you can just observe the patient for a while. If the misalignment causes a dimu- nition in vision, Dr. Lane recom- mended treating the patient within a few days or a week. 7. Decide in advance how you will handle post-op touch ups. You can use PRK or LASIK, or you can do an astigmatic arcuate cut with the new femtosecond cataract lasers, Dr. Trattler said. If the patient's astigma- tism is off, you can rotate the lens, he added. "There are different steps you can take, but you have to be ready to know what you can do," he said. 8. Always dilate the eye at 1 day post-op to see the location of the lens, Dr. Ernest said. That way, you can make sure the IOL is where you want it to be. If it was improp- erly placed or if it has rotated, it's much easier at 1 day post-op to fix any problems than it is after, say, the 2- to 3-week mark. Plus, if you are fixing the problem on day 1 post-op, you usually don't have to add any more viscoelastic material to the eye. If the IOL is going to rotate, it almost always does so either the day of surgery or 1 day thereafter, Dr. Ernest said. In the thousands of im- plantations Dr. Ernest has done, he's only treated two cases where the IOL inexplicably rotated more than a couple of days after surgery. EW Editors' note: Dr. Lane has financial interests with Alcon (Fort Worth, Texas), SMI (Teltow, Germany), and WaveTec. Dr. Trattler has financial interests with Abbott Medical Optics (AMO, Santa Ana, Calif.) and Carl Zeiss Meditec. Dr. Ernest has no financial interests related to this article. Contact information Ernest: paul.ernest@tlcvision.com Lane: 651-275-3000, sslane@associatedeyecare.com Trattler: 305-598-2020, wtrattler@gmail.com