EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/78788
February 2011 August 2012 EW REFRACTIVE SURGERY 33 Cutting intrastromally by Enette Ngoei EyeWorld Contributing Writer New way of creating arcuate incisions shows promise in correcting astigmatism I ntrastromal arcuate incisions using the IntraLase femtosec- ond laser (Abbott Medical Optics, AMO, Santa Ana, Calif.) for the correction of astigma- tism produce safe and precise results, according to one of the first re- searchers of the procedure, Gunther Grabner, M.D., professor of ophthalmology and chairman, Uni- versity Eye Clinic, Paracelsus Med- ical University, Salzburg, Austria. Because it doesn't cut through Bowman's layer, the laser treatment eliminates the danger of infection, wound gape, or epithelial ingrowth, said Perry S. Binder, M.D., clinical professor, Gavin Herbert Depart- ment of Ophthalmology, University of California, Irvine. Performed intrastromally with the laser, these incisions don't dam- age the epithelium, the superficial nerves, or Bowman's membrane, and no loss of endothelial cells has been observed, Dr. Grabner said. "It is much more stable than with the diamond knife, and it does not cut as many corneal nerves so you don't get problems with vascu- larization, loss of sensitivity, dry eyes that are induced with LRIs. It's very fast—something like two inci- sions last about 12 seconds. It's pain- less, and the patient is back to work half an hour later," he said. Correctability Preliminary data from separate stud- ies done by Dr. Grabner and another early researcher, Roberto Zaldivar, M.D., scientific director, Zaldivar Institute, Argentina, shows that on the average, between 1.0 and 1.5 D of correction is obtained, said Dr. Binder. "The reader might say that's a lot less than you would get when you incise with the diamond blade to the full thickness of the cornea and that's correct, but the range, the minimum amount and the maxi- mum amount, was much smaller when we operate within the cornea so our predictability is better," he said. "We're very positive and excited about this," he added. It can also be used for treating such cases as keratoconus and post- corneal transplantation so that after the treatment, patients may benefit from spectacles or contact lenses by reducing their astigmatism, Dr. Binder added. Patients who would not be good candidates for the procedure include those who have had previous inci- sions within the cornea, be they radial keratotomy or astigmatic keratotomy, he said. He also wouldn't use it in peo- Intrastromal arcuate incisions performed with the IntraLase (pictured here) produce safe and precise results, according to recent research Source: Howard Kornstein, M.D. To overcome the potential problem that the procedure corrects less than the standard incision, Dr. Gunther said that he and colleagues are working on nomograms with double incisions and possibly even triple incisions so that more correc- tion might be obtained with more incisions. Potential risks The potential problem with any intrastromal procedure is the pre- dictability of where the laser's going to cut, Dr. Binder said. If the laser cuts too superficially, it isn't a prob- lem. However, if it perforates posteri- orly, then it's analogous to hydrops of the cornea, he said. If it simultaneously perforates the front and the back of the cornea, which is a hard thing to do, then there would have to be stitches in the front part of the cornea to seal that up, he added. Other risks include those typi- cally associated with any refractive procedure—too little correction or too much correction, Dr. Binder said. "Since this is a relatively new procedure, we're developing and understanding its predictability, so these incisions are placed at differ- ent diameters, there are different arc lengths, size, you could place one or two, and then there's a sidecut. In- stead of a steady incision perpendi- cular to the cornea, the surgeon [can decide he wants] this angulated; the reason to do that is if you cut at an angle, you're increasing the surface that's cut to increase the affectivity of the procedure," he explained. The good news, he said, is staying within the cornea reduces or eliminates the risks of epithelial ingrowth, instability of refraction, risk of infection, recurrent corneal erosion, and instability of the procedure. Indications The procedure can be beneficial to a number of different patients, includ- ing those with naturally occurring astigmatism. Patients undergoing cataract surgery, be it for monofocal, multifocal, or even toric IOLs (whether prior to surgery, during, or after surgery to correct any minimal astigmatism that might remain), will benefit from these incisions as well, Dr. Binder said. ple with corneal scars because fem- tosecond lasers don't go through corneal scars very well, their energy is dissipated, and focus is decreased, he explained. Patients with irregu- larly thin corneas, previous trauma, highly advanced keratoconus, or pellucid marginal degeneration are also not good candidates for the incisions. Ongoing work AMO is currently sponsoring a mul- ticenter prospective study outside of the U.S. to evaluate the safety and effectiveness of arcuate incisions performed with the IntraLase femtosecond laser, Dr. Binder said. EW Editors' note: Drs. Binder and Grabner have financial interests with AMO. Contact information Binder: 858-922-8699, garrett23@aol.com Grabner: g.grabner@salk.at Modified DSAEK technique may cause less endothelial cell damage A Japanese researcher is touting a modified surgical technique that optimizes the use of a Busin glide for Descemet's stripping automated endothelial keratoplasty (DSEK) and may lessen endothelial cell damage as a result. Prewetting the glide and hydrodissecting the very thin donor lamella lessens the chances of wrinkles or folds when loading the lamella onto the glide, according to lead researcher Akira Kobayashi, M.D., Department of Ophthalmology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan, who reported his findings in the July issue of Clinical Ophthalmology. "This technique is quite useful when the DSAEK is performed using precut tissue, as these tissues are usually distributed with the cap adhered to the dissected stromal bed. In 10 out of 10 consecutive cases, we saw that simply dragging donor-endothelial lamella directly onto the glide caused macroscopic wrinkling or folding of the donor lamella," Dr. Kobayashi said in the report. "Furthermore, prewetting of the glide enabled quite smooth pull-through of the donor lamella in all cases."