EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/111385
54 EW FEATURE February 2011 Refractive/astigmatism February 2013 Correcting continued from page 52 LRIs Last year���s ASCRS Innovator���s Lecture clarified what ���posterior corneal astigmatism��� is (courtesy of Douglas Koch, M.D.). Dr. Nichamin said ���one of the ramifications of [this work] is that we now have further evidence that with-the-rule (WTR) astigmatism behaves differently than ATR, and that���s due in part to the posterior corneal contributions.��� Dr. Nichamin���s LRI nomo- grams have ���for many years��� been divided into two separate tables��� one for WTR and the other for ATR. ���I���m probably a bit of an anomaly because I separate them���it���s not significantly different, and almost in the same ratio as what [Dr. Koch] has pointed out in terms of quantified differences that occur in the posterior corneal measurements in the setting of toric IOL use,��� Dr. Nichamin said. As such, Dr. Koch���s Caution: United States Federal Law restricts this device to sale and use by or on the order of a physician or licensed eye care practitioner. Indication: The LenSx�� Laser is indicated for use in patients undergoing cataract surgery for removal of the crystalline lens. Intended uses in cataract surgery include anterior capsulotomy, phacofragmentation, and the creation of single plane and multi-plane arc cuts/incisions in the cornea, each of which may be performed either individually or consecutively during the same procedure. Restrictions: t t t t 1BUJFOUTNVTUCFBCMFUPMJF��BUBOENPUJPOMFTTJOBTVQJOFQPTJUJPO 1BUJFOUNVTUCFBCMFUPVOEFSTUBOEBOEHJWFBOJOGPSNFEDPOTFOU 1BUJFOUTNVTUCFBCMFUPUPMFSBUFMPDBMPSUPQJDBMBOFTUIFTJB 1BUJFOUTXJUIFMFWBUFE*01TIPVMEVTFUPQJDBMTUFSPJETPOMZVOEFSDMPTFNFEJDBM supervision. 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Precautions: t %POPUVTFDFMMQIPOFTPSQBHFSTPGBOZLJOEJOUIFTBNFSPPNBTUIF-FO4Y��-BTFS t %JTDBSEVTFE1BUJFOU*OUFSGBDFTBTNFEJDBMXBTUF AEs/Complications: t $BQTVMPUPNZ QIBDPGSBHNFOUBUJPO PSDVUPSJODJTJPOEFDFOUSBUJPO t *ODPNQMFUFPSJOUFSSVQUFEDBQTVMPUPNZ GSBHNFOUBUJPO PSDPSOFBMJODJTJPOQSPDFEVSF t $BQTVMBSUFBS t $PSOFBMBCSBTJPOPSEFGFDU t 1BJO t *OGFDUJPO t #MFFEJOH t %BNBHFUPJOUSBPDVMBSTUSVDUVSFT t "OUFSJPSDIBNCFS��VJEMFBLBHF BOUFSJPSDIBNCFSDPMMBQTF t &MFWBUFEQSFTTVSFUPUIFFZF ��/PWBSUJT -49+"% recent findings with regard to ATR versus WTR astigmatism and its varying response to correction through the use of toric implants parallels what he has experienced when utilizing LRIs. ���There���s still much that we don���t understand and until recently, did not measure very well either.��� For instance, the limbus is a little closer to the visual axis at 6 and 12 o���clock as compared to 9 and 3 o���clock, and ���inter-��� as well as ���intra���-corneal meridional differences can complicate calculations; traditional measurements tend to occur only at two points in each meridian, which may not be sufficient. Surgeons have also seen meridional differences between Occidental and Asian eyes. ���I���ve been a big proponent of LRIs for a long time, but one of the concerns with these incisions is that every patient responds differently based on multiple parameters,��� Dr. Donnenfeld said, adding Dr. Koch���s work has helped to clarify some of those discrepancies. ���It���s more of an art form than science, and LRI results can be variable even in the hands of the best surgeons because of the patient variability.��� LRIs remain a reasonable option for anything under 1.0 D or 1.5 D, Dr. Tipperman said, but ���based on Dr. Koch���s work, maybe we should limit that to 0.75 D or 1.25 D if they���re WTR.��� Dr. Nichamin suggested that all surgeons continually adjust and refine their nomograms and start thinking of them as fluid measurements rather than static ones. Femtosecond laser Dr. Donnenfeld has begun performing arcuate incisions with a femtosecond laser ���because the accuracy is uncanny,��� he said. ���The incisions are perfectly symmetric so there is less irregular astigmatism and none of the surgeon variability that can be present with manual LRIs.��� With the LenSx (Alcon), he uses a 9 mm optical zone, and an 8 mm optical zone with the IntraLase (AMO). By titrating the incisions, ���we���re achieving superior outcomes. Before the femtosecond laser, any incision we made was permanent,��� he said. The femtosecond laser allows surgeons to create the incision but not fully open it until deemed necessary, either intraoperatively or post-op, allowing the surgeon to adjust the results. ���You don���t have to open the incisions at the time of surgery,��� Dr. Tipperman said. ���One of the biggest advantages of the femto incision is that it���s adjustable and titratable.��� He treats at 9 mm, and ���I use 90% of the nomogram and about 85% depth.��� Dr. Nichamin has worked with the LensAR (Orlando, Fla.) laser and although FDA approval for relaxing incisions is still pending, in the laboratory ���we have been able to create near perfect incisions all the way out to the limbus in most cases.��� ASCRS is working on developing nomograms for the different femtosecond lasers/arcuate incisions. Toric IOLs Toric IOLs are still the preferred treatment if patients have undergone previous refractive surgery, have higher levels of astigmatism, or have thin corneas, Dr. Nichamin said. ���Toric IOLs have been our game changer in astigmatism management��� because of their stability and predictability, Dr. Tipperman said. ���I like toric lenses,��� Dr. Donnenfeld said. ���They don���t have the incisions, they don���t induce dry eye, and they���re more accurate for higher amounts of astigmatism.��� He routinely combines arcuate incisions with toric IOLs and uses the former as a template for where to place the lens; he opens the incisions post-op ���if I need to do any fine-tuning.��� Dr. Tipperman suggests marking at 6 o���clock using a circular marker and ensuring the viscoelastic is removed at the end of the procedure to avoid post-op rotation. ���For surgeons to achieve optimal results, they need to be familiar with all of these treatment modalities,��� Dr. Nichamin said. ���You can���t hang your hat on just one.��� The decision of which technique to use ���is quite complex, and there���s not one quick, simple answer. It depends on the surgeon���s comfort level, what technologies are readily available, cost, and perhaps most importantly, specific patient characteristics.��� EW Editors��� note: Dr. Donnenfeld has financial interests with Alcon and AMO. Dr. Nichamin has financial interests with LensAR. Dr. Tipperman has financial interests with Alcon and Marco (Jacksonville, Fla.). Contact information Donnenfeld: 516-766-2519, ericdonnenfeld@gmail.com Nichamin: 814-849-6547, ldnichamin@aol.com Tipperman: 484-434-2716, rtipperman@mindspring.com