Eyeworld

EW FEATURE 44 "If you don't calibrate the ma- chines regularly, you introduce sig- nificant error in your calculations," Dr. Rapoza said. "Calibrating the keratometers is one area where surgeons are a little negligent," Dr. Lindstrom said. For example, he said with the Bausch & Lomb (Rochester, N.Y.) keratometer, instead of taking simply the plus and negative readings—and know- ing the plus readings are more accu- rate than the negative readings— "you need to actually take a reading and rotate 90 degrees overlapping the plusses and then do it again. And then you need to accurately set the system for your refraction," he said. Aside from calibration, "be cer- tain the eye you're approaching is ready for testing," Dr. Rapoza said. Patients undergoing refractive sur- gery screening are expected to be out of contact lenses for 2-4 weeks (depending on the type of lens the patient uses), and "surgeons have to let the cornea return to the normal shape for IOL calculations as well. If you try to measure on the day the patient walks in wearing lenses, you're going to introduce error into your calculations," he said. Dr. Rapoza uses manual Ks, immersion A-scans, and the IOLMaster. "If there's a discrepancy, we need to determine the reason for it—we might have missed anterior basement membrane dystrophy or significant dry eye," he said. Having dedicated diagnostic technicians means the technician will some- times pick up a significant epiretinal membrane or macular disturbance because the patient has a poor echo, he added. "Stack the deck in your favor and make sure you take all the meas- urements very carefully on as pris- tine an eye as possible," he said. Dr. Thompson said the ability to measure intraoperatively "both in the aphakic state and once the lens is in there, settled close to its final resting position and close to its ef- fective lens position" has been an invaluable addition to diagnostics. "The fact of the matter is, the capsule does contract, and there is a little bit of lens movement just from that contraction. I use the WaveTec ORange (Aliso Viejo, Calif.), which gives me the refraction while I'm in the OR," he said. The "major problem" is that even if a surgeon is meticulous in the pre-op measurements, "there's no way to accurately predict what the final effective lens position will be," Dr. Lindstrom said. "It's only manageable with intraoperative aberrometry and even then it's not easily manageable." The ORange "may be the way to go," Dr. Rapoza said, "but it still needs a little more fine-tuning. As- sessing the eye on the table is a great way to go. The downside is it does add time and an additional step to the surgical procedure. But at the same time, if that alleviates having to do a laser vision enhancement procedure, and you end up with a happier patient and not having to do a lens exchange, I think it's going to be beneficial." Where we're heading Dr. Lindstrom believes the next step will be "some form of on-the-table measurement" for toric IOLs. "Toric IOL planners need to be a little more sophisticated," he said, adding the next generation toric IOL calculator should be available within 6 months and will include features such as in- corporating the baseline IOL power and corneal curvature. (He noted Dr. Holladay recently presented the Strempelli Lecture on the topic in Italy.) The post-refractive surgical cases with no pre-op data "are still the most difficult," Dr. Thompson said. "It's critical the patient understands the difficulty in predicting the re- fractive outcome in this case, and the informed consent needs to be crystal clear on that. In the end, you might still have to do an implant ex- change, but our measuring abilities, our formulas, and our intraoperative ability to check and double check our calculations are much better now than they were a decade ago." Dr. Thompson said the potential to use optical coherence tomogra- phy "to measure behind the iris and image the natural lens and correlate that with the post-op implant lens position" will help surgeons better estimate the effective lens position, thereby improving outcomes. Dr. Lindstrom said SMI (Teltow, Germany) is working on an iris reg- istration model that will allow sur- geons to know "exactly where the steeper axis is on the eye," which eliminates the concerns of a toric implantation in an eye that's ro- tated. He said Clarity (San Francisco) is developing "an on-the-microscope aberrometer that will give more rapid real-time readings." The typi- cal surgeon is 5-10 degrees off axis post-toric IOL implantation, which can result in a decrease of 15-33% in the lens power. "Intraoperative measurements are the next step to getting toric lenses right on axis and may be able to improve our defocus curves as well," Dr. Lindstrom said. Ideally, Dr. Rapoza said, sur- geons want measurements on "the patient without significant ocular disease, with contacts out for an ad- equate period of time, and examined on equipment that's well calibrated by a technician who is well trained and attentive," he said. "It's so easy to make a mistake." Dr. Thompson expects advances on both ends of the spectrum, with formulas continuing to evolve and improvements in the ability to measure corneal curvatures in post- refractive states. "As we get better at effective lens position, intraoperative meas- urements will become more and more accurate. Those are the main areas where we still need improve- ment," he said. EW Editors' note: Dr. Lindstrom consults for industry and has financial interests with WaveTec Vision and Clarity. Dr. Rapoza has no financial interests re- lated to his comments. Dr. Thompson has financial interests with Abbott Medical Optics (Santa Ana, Calif.), Alcon (Fort Worth, Texas), Bausch & Lomb (premium lenses only), and WaveTec Vision. Contact information Lindstrom: 952-567-6051, rllindstrom@mneye.com Rapoza: 617-314-2684, parapoza@eyeboston.com Thompson: 605-328-3937, vance.thompson@sanfordhealth.org February 2011 Ethics of IOLs August 2011 I n the majority of responses (83%), the surgeon undertakes the time-consuming task of counsel- ing the patient regarding premium IOLs. Even with newer counseling tools that should allow the discussion to be led by a staff member, this finding reflects the importance that is placed on the pre-op discussion. It is also interesting to note the trend away from mixing different technologies of presbyopia-correcting IOLs, which was more popular several years ago. - Bonnie An Henderson, cataract editor I am a bit surprised, and encouraged, that 83% of doctors are taking the time to talk about pre- mium IOLs directly with their patients rather than having staff do this job. I feel that the choice of implant should be a surgeon's recommendation made after evaluating the patient completely rather than a sales pitch by the staff that starts in the waiting room. I was also impressed that al- most a quarter of surgeons are using premium IOLs in over 25% of their patients. I suspect this number is a bit higher than what's going on in the real world. The crowd taking the poll may be a bit more progressive than the general population. Most of the other preferences seem pretty reason- able and consistent with what I'd expect. - Steve Safran, cataract editorial board member Monthly Pulse Keeping a Pulse on Ophthalmology Pre-op continued from page 43

• Cover