EyeWorld Asia-Pacific September 2012 Issue

54 September 2012 EWAP DEVICES beneath the donor, through the wound, to prevent descent of the donor onto the iris, and only then should the donor be released from the forceps. Full wound closure, centration of the donor, a complete air tamponade, and completion of the DSAEK procedure may then be performed in the usual manner. EndoGlide Ultrathin (UT) version With increasing use of thinner donor tissue (ultrathin DSAEK) to sub-100-micron thicknesses, which may result in better vision, a second version of the EndoGlide, EndoGlide Ultrathin (UT), has been designed, with improved ease of donor coiling for thinner tissues between 50-100 microns. It incorporates a detachable coiling saddle with a conical front end that enables easy coiling without the need to stroke the sides of the donor upward in most cases, unless the donor is less than 50 microns. The EndoGlide UT also has a higher donor well platform, which allows for placement of just the posterior lenticule in situations where only the posterior lenticule is supplied by the eye bank. The EndoGlide UT may also be used for thicker donor tissue (100-250 microns). Technique of donor loading using the EndoGlide UT: Fill the well and the cartridge with balanced salt solution and place both the anterior and posterior lenticules of the donor in the well. Gently remove the anterior lenticule and position the posterior lenticule adjacent to the cartridge opening. Once the donor is close to the entrance, it may then be further drawn toward the cartridge opening by wicking away balanced salt solution from the front of the cartridge, using a dry Weck cell sponge placed at the front open end of the cartridge. As fluid is drawn forward through the cartridge chamber into the sponge, the donor will usually also be drawn by capillary action right up to the entrance of the cartridge. Place a thin strip of dispersive viscoelastic onto the donor, and pull the donor into the cartridge with the straight loading EndoGlide forceps (Figure 4). As the donor tissue enters the capsule, the sides of the donor tissue will naturally curl upward, without wrinkling, along the upward curving walls of the saddle tunnel, and the tissue will form a double coil configuration in the cartridge. Unlike the EndoGlide Classic, it is usually unnecessary to use a cannula to stroke the edges of the donor upward along the sidewalls of the chamber, unless the donor is extra thin (e.g., sub-50 microns). Remove the detachable transparent saddle, and attach the introducer to the back of the cartridge and remove from the preparation base for insertion. Early clinical results with the EndoGlide UT have been encouraging with no cases of graft dislocation or graft failure in the first 20 cases (unpublished data). Another advantage of the EndoGlide donor inserter is the possibility of precut and preloaded donor delivery by eye banks, which further simplifies DSAEK surgery for surgeons. A recent study presented at the 2012 ASCRS•ASOA Symposium & Congress showed there was minimal cell damage after the donor corneas were stored for 24 hours preloaded in the EndoGlide. Following our initial wet lab work, we are using precut and preloaded donors for our clinical cases. More data will be required to confirm our early positive safety and efficacy results. EWAP Editors’ note: Dr. Tan is medical director, Singapore National Eye Centre. He has financial interests with Angiotech, Alcon (Fort Worth, Texas, USA/Hünenberg, Switzerland), Bausch + Lomb (Rochester, NY, USA), Santen (Osaka, Japan), Moria (Antony, France), Carl Zeiss Meditec (Jena, Germany), AcuFocus (Irvine, Calif., USA), and Technolas Perfect Vision (Munich, Germany). Contact information Tan: snecdt@pacific.net.sg “The biomechanical frontier is the next step to the refractive surgery evolution,” Dr. Fontes said. “We need it not only to screen for ectasia risk but to develop an individual nomogram to modulate laser energy for each patient.” Further, the group has acted like a watchdog, ensuring that corneal analysis tools like the Ectasia Risk Score System (ERSS) receive appropriate discussion and deliberation. For instance, Dr. Ambrosio and Michael W. Belin, MD, published an editorial on the ERSS in the Journal of Refractive Surgery in April 2010, noting that 8% of LASIK cases develop ectasia despite a low ERSS score, and there is “a false positive rate as high as 35% if a relatively young population is evaluated.” Tomography vs. topography When the study group started, Dr. Ambrosio didn’t have tomography capability. “I knew I needed it, but I was doing LASIK without it,” Dr. Ambrosio said. Yet he desired something that went beyond current refractive screening for LASIK candidates. “I saw many cases of ectasia that didn’t have an explanation,” Dr. Ambrosio said. Keratoconus itself is a common disease, Dr. Ambrosio said. “It’s more common than the 1 in 2,000 figure reported in the literature,” he said. Even topography could not help to always properly screen refractive surgery candidates. Hence, Dr. Ambrosio developed an interest in spearheading education about tomography versus topography, publishing a guest editorial on this subject in the Journal of Refractive Surgery in November 2010. One important distinction, he said, is that topography refers to analyzing a place on the surface of the cornea, while tomography could go so far as to create a 3D virtual reconstruction of different parts of the cornea including the thickness and front and back elevation. Dr. Ambrosio then referred to a case presentation from Cornea Day at the 2012 ASCRS•ASOA Symposium & Congress. “This is an example of a case that had ectasia after LASIK in spite of the relatively low risk based on standard screening methods,” Dr. Ambrosio said. “Tomography would have detected the risk.” Research in practice Dr. Fontes recalls one company in 2006 that promoted an exact measure of corneal strength without doing appropriate research on the topic. “There were some sponsored papers in this area,” Dr. Fontes said. “Our papers were the first ones published in highly respected journals such as Ophthalmology showing [that measure] has some limitations. We studied the topic deeply and people started to take notice.” The result was that the company began looking at ways to improve its machine and whether it could deliver other information. “I don’t think corneal hysteresis has so much value now,” Dr. Fontes said. “It’s more commercial without much scientific research. “ That said, the subject of corneal hysteresis did open a new door for measuring corneal strength that has led to improved measurements, he said. Today, the group continues to generate knowledge about corneal architecture, anatomy in healthy and pathologic corneas, and tries to study in-depth corneal strength and its response to deformation. It also continues to study corneal biomechanics and tomographic indices to improve knowledge in the field. EWAP Editors’ note: Dr. Ambrosio has financial interests with Oculus (Lynnwood, Wash., USA). Dr. Fontes has no financial interests related to his comments. Contact information Ambrosio: dr.renatoambrosio@gmail.com Fontes: brunomfontes@terra.com.br At the heart - from page 49 EndoGlide - from page 52