Eyeworld

EW FEATURE 34 Even in the cataract population, "many surgeons feel that they can correct somewhere around 1.5 D of astigmatism on the cornea with an LRI alone," Dr. Weinstock said. "Relaxing incisions aren't even an option with some post-LASIK eyes and are quite limited in cases of previous RK," said Mark Packer, M.D., clinical associate professor of ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland. "In post-RK eyes, if there's a large enough optical zone and some regular astigmatism within the optical zone, then I'll use a toric." Dr. Osher first introduced astig- matic keratotomy in 1983, and "it remains an effective technique that will reduce astigmatism" in conjunc- tion with cataract surgery. But out- comes are variable and rely on patient healing times, he said, and he was quick to embrace toric IOL technology. "I perform astigmatic reduction in over 50% of my routine cataract patients, and 27% of those are torics," he said. Challenges today Irregular astigmatic patterns and de- termining the axis of astigmatism remain the two biggest challenges. Occasionally K readings from an IOLMaster (Carl Zeiss Meditec, Dublin, Calif.) may not align with topography, Dr. Trattler said. Online calculators such as the LRIcalculator.com (Abbott Medical Optics, AMO, Santa Ana, Calif.) can be useful as well, he added. "There's a lot out there to meas- ure corneal astigmatism but no sin- gle instrument that will give the right answer all the time," Dr. Lane said. "I can do all the diagnostic tests I want, but I still have to pick a number." Some surgeons prefer to use a pen to mark the axis pre-op and use it as a reference during surgery. Oth- ers prefer to use digital markers be- cause they can provide more accurate data on the true vertical and horizontal meridians, Dr. Weinstock said. Dr. Osher uses iris fingerprint- ing, noting ink can lead to "huge amounts of inaccuracy" in the cor- rection. "I know from my fingerprinting where the major meridia are, so it's very easy for me to take a semi-lunar marker and snuggle it right up to the limbus and be very accurate," he said. "While I also use ink, I don't rely on it." Newer diagnostic tools Dr. Osher developed the Micron Imaging Systems (Pegram, Tenn.), which can identify the number of degrees for any iris landmark accu- rately with software applied to a dilated pupil. He believes iris land- marks (pigment, nevi, stromal pat- terns, vessels, Brushfield spots, etc.) are more reliable "because vascular landmarks can change after dilating drops." He also developed the Osher Alignment Toric System (Haag-Streit, Koeniz, Switzerland), but does not retain a financial interest in either version. With the TrueVision 3D System (Santa Barbara, Calif.), an overlay template gives the "exact location for the lens," Dr. Weinstock said. "You take a pre-op photo to find the primary meridians. In the OR, I im- port the data and align it by limbal vessel registration. It eliminates con- cerns about cyclotorsion on the table." A major benefit of the system is that surgeons can look through the microscope, but also at a screen with a superimposed reticle on the limbus to track and show where the axis is, he said. The WaveTec ORA (Aliso Viejo, Calif.) also uses a reticle and real- time imaging. In post-keratorefrac- tive eyes, "I use the ORA to align the toric lens to its optimal location, which may be different after I've made the incisions," Dr. Packer said. He cites an advantage of the system is the ability to measure corneal astigmatism intraoperatively. SensoMotoric Instruments (SMI, Teltow, Germany) uses a pre-op ker- atometry measurement in combina- tion with a high-res image of the patient's eye to register the limbal blood vessels and iris details, Dr. Lane said, meaning the surgeon has registered the eye as soon as the pa- tient is in the supine position. "It saves all the pre-op mark- ings, so during surgery there are no ink marks, no dilution from ink pens. It's an incredibly accurate tool that lets me put the lens on the axis I determined pre-op," he said. Dr. Lane puts the lens into position ac- cording to the SMI, and then re- measures with the ORA to ensure he's hit the mark. Dr. Osher is also a fan of the SMI technology. He is working with Stephen G. Slade, M.D., and David F. Chang, M.D., to develop Holos (Clarity Medical Systems, Pleasan- ton, Calif.), "an intraoperative wave- front, dynamic scanning, real-time device," he said. "It offers real-time feedback on meridian location for better lens alignment." The iTrace (Tracey Technologies, Houston) gives surgeons the ability "to see where to line up the IOL in relation to the astigmatic axis on the topography," Dr. Trattler said. Post-op surprises Dr. Weinstock said the STAAR toric lens (Monrovia, Calif.) and the Alcon toric lens (Fort Worth, Texas) each have advantages and disadvan- tages. The STAAR lens is easy to ma- nipulate, but can also rotate more easily post-op. The Alcon lens is more challenging to position, but re- mains in place post-op. "Even after doing everything right intraoperatively, some will still need an enhancement. My enhance- ment rate is 4% with incisions (actu- ally less than with LASIK), and that's using the WaveTec ORA wavefront aberrometry," Dr. Packer said. Surgeons are getting better at managing astigmatism, "and we've got great technologies for when we're not on target—LRIs, LASIK, or PRK," Dr. Trattler said. "We have tools today that make correcting astigmatism easier," Dr. Lane said, but surgeons still need to weigh the costs of these tools against the improved accuracy. "All patients who have signifi- cant astigmatism should be given the opportunity to reduce their cylinder at the time of their cataract surgery," Dr. Osher said. "We now have the technology to achieve in the OR what has been previously ac- complished with spectacles." EW Editors' note: Dr. Lane has financial in- terests with Alcon, SMI, and WaveTec. Dr. Osher consults for industry, but has no financial interests related to this ar- ticle. Dr. Packer consults for industry. Dr. Trattler has financial interests with AMO and Carl Zeiss Meditec. Dr. Weinstock has financial interests with WaveTec and TrueVision. Contact information Lane: 651-275-3000, sslane@associatedeyecare.com Osher: 800-544-5133, rhosher@cincinnatieye.com Packer: 541-687-2110, mpacker@finemd.com Trattler: 305-598-2020, wtrattler@gmail.com Weinstock: 727-244-1958, rjweinstock@yahoo.com February 2011 What's ahead in 2012 December 2011 Aligning continued from page 33 The iTrace can help surgeons plan their astigmatic corrections Source: William B. Trattler, M.D. The SMI shows surgeons the location of the axis Source: SensoMotoric Instruments

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