EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/194331
October 2013 Views from Asia-Pacific: DSAEK vs. DMEK IMPORTANT SAFETY INFORMATION FOR THE VERION™ REFERENCE UNIT AND VERION™ DIGITAL MARKER CAUTION: Federal (USA) law restricts this device to sale by, or on the order of, a physician. INTENDED USES: The VERION™ Reference Unit is a preoperative measurement device that captures and utilizes a high-resolution reference image of a patient's eye in order to determine the radii and corneal curvature of steep and flat axes, limbal position and diameter, pupil position and diameter, and corneal reflex position. In addition, the VERION™ Reference Unit provides preoperative surgical planning functions that utilize the reference image and preoperative measurements to assist with planning cataract surgical procedures, including the number and location of incisions and the appropriate intraocular lens using existing formulas. The VERION™ Reference Unit also supports the export of the high-resolution reference image, preoperative measurement data, and surgical plans for use with the VERION™ Digital Marker and other compatible devices through the use of a USB memory stick. Alvin L. Young, FCOphth, FRCOphth The VERION™ Digital Marker links to compatible surgical microscopes to display concurrently the reference and microscope images, allowing the surgeon to account for lateral and rotational eye movements. In addition, the planned capsulorhexis position and radius, IOL positioning, and implantation axis from the VERION™ Reference Unit surgical plan can be overlaid on a computer screen or the physician's microscope view. CONTRAINDICATIONS: The following conditions may affect the accuracy of surgical plans prepared with the VERION™ Reference Unit: a pseudophakic eye, eye fixation problems, a non-intact cornea, or an irregular cornea. In addition, patients should refrain from wearing contact lenses during the reference measurement as this may interfere with the accuracy of the measurements. Only trained personnel familiar with the process of IOL power calculation and astigmatism correction planning should use the VERION™ Reference Unit. Poor quality or inadequate biometer measurements will affect the accuracy of surgical plans prepared with the VERION™ Reference Unit. The following contraindications may affect the proper functioning of the VERION™ Digital Marker: changes in a patient's eye between preoperative measurement and surgery, an irregular elliptic limbus (e.g., due to eye fixation during surgery, and bleeding or bloated conjunctiva due to anesthesia). In addition, the use of eye drops that constrict sclera vessels before or during surgery should be avoided. WARNINGS: Only properly trained personnel should operate the VERION™ Reference Unit and VERION™ Digital Marker. Only use the provided medical power supplies and data communication cable. The power supplies for the VERION™ Reference Unit and the VERION™ Digital Marker must be uninterruptible. Do not use these devices in combination with an extension cord. Do not cover any of the component devices while turned on. Only use a VERION™ USB stick to transfer data. The VERION™ USB stick should only be connected to the VERION™ Reference Unit, the VERION™ Digital Marker, and other compatible devices. Do not disconnect the VERION™ USB stick from the VERION™ Reference Unit during shutdown of the system. The VERION™ Reference Unit uses infrared light. Unless necessary, medical personnel and patients should avoid direct eye exposure to the emitted or reflected beam. PRECAUTIONS: To ensure the accuracy of VERION™ Reference Unit measurements, device calibration and the reference measurement should be conducted in dimmed ambient light conditions. Only use the VERION™ Digital Marker in conjunction with compatible surgical microscopes. ATTENTION: Refer to the user manuals for the VERION™ Reference Unit and the VERION™ Digital Marker for a complete description of proper use and maintenance of these devices, as well as a complete list of contraindications, warnings and precautions. © 2013 Novartis 9/13 VRN13015JAD-PI Tae-Im Kim, MD I n the January 2013 issue of EyeWorld, cornea surgeons came together to compare thin Descemet's stripping automated endothelial keratoplasty and Descemet's membrane endothelial keratoplasty as options for endothelial keratoplasty procedures. "DSEK involves a transplant of the back layers of a donor cornea into a patient's eye. This technique offers a certain ease because it has been the procedure of choice for many years. DSAEK is the automated version of this procedure, which uses a machine to cut tissue," the article said. "DMEK, on the other hand, uses extremely thin donor tissue, with a better chance of restoring good vision to the patient. However, surgeons using this technique often experience obstacles with handling the donor tissue because of how fragile the grafts can be. Recently, thin DSAEK has offered an alternative to the other two techniques, utilizing the ease of DSAEK with thinner grafts." In our sister publication, EyeWorld Asia-Pacific, Alvin L. Young, FCOphth, FRCOphth, of Hong Kong, and Tae-Im Kim, MD, of Korea, shared their thoughts on the techniques. Dr. Young: There has been a major paradigm shift in the field of corneal transplantation since the advent of modern endothelial keratoplasty. The popularity of the technique has been widespread. One of the main reasons for the immense positive response toward this surgery is the relative ease of performing the whole procedure. In the earlier days, DLEK (deep lamellar endothelial keratoplasty) surgery was technically more demanding and difficult, hence subsequently replaced by DSEK. Most corneal surgeons are now using DSEK or DSAEK depending upon the availability of an automated microkeratome or precut tissue in their setup. More recently, the focus of discussion has shifted to the use of thin donor lenticules, consequently bringing ultra-thin DSAEK and DMEK to the forefront. However, there are certain pertinent issues that need to be considered before these relatively new surgeries can be adopted. Obtaining a thin cut donor lenticule or only the Descemet's membrane (in DMEK) can be a difficult proposition resulting in inadvertent wastage of human tissue, which certainly is not affordable in countries where there is an obvious dearth of donor corneas. In addition, using two microkeratome heads for ultra-thin DSAEK lenticules would impose extra financial burden in less affluent economies and especially when these heads are disposable. Furthermore, Asian eyes are commonly found to have shallow anterior chambers, limiting the freedom of movement inside the eye when the surgeon is trying to "center" or orientate a very thin donor lenticule. The situation becomes worse if another intervention, such as refloating the graft, is required. At the moment, there is still a relative scarcity of reports on excellent visual outcomes after thin lenticule DSAEK or DMEK. In the absence of any long-term comparative clinical trials, one needs to weigh the benefits and risks that are local in terms of graft availability, preparation, wastage rate, patient factors, and surgeons' expertise in deciding whether or not to adopt thin lenticule DSAEK, DMEK, or to "settle" with a fairly confidently attainable visual acuity of 20/30 with conventional DSEK/DSAEK. As mentioned earlier, the ease of performing a conventional DSEK/ DSAEK is one of the highlights of this surgery. Further research and refinement in innovation of better technology and techniques aimed at the better and safer preparation of donor material (perhaps best served by an eye bank), surgical handling of donor and its insertion are warranted. Dr. Kim: Over the years, keratoplasty has been developed and has recently diversified from penetrating keratoplasty (PK) to refined lamellar keratoplasty. Anterior stromal corneal abnormality was corrected by lamellar keratoplasty or deep lamellar keratoplasty using various techniques. The posterior part of the cornea abnormality, mainly related to endothelial dysfunction, was treated by selective replacement of diseased recipient endothelium via Descemet's stripping endothelial keratoplasty (DSEK) or Descemet's membrane endothelial keratoplasty (DMEK). In Descemet's stripping automated endothelial keratoplasty (DSAEK), the outer layers of the cornea are skimmed off using a mechanical microkeratome, leaving a very thin layer of stromal fibers supporting the inner Descemet's membrane and the endothelial cells. The bottom 20% of divided cornea is used for DSAEK and the top 80% can be used as donor tissue for anterior lamellar transplants. Automated cutting improves the donor preparation procedure with smooth cut surfaces and predictable thickness. The quality of the visual recovery after DSAEK is generally better than that achieved by a penetrating graft. The stability of the refraction and rapid visual rehabilitation are major advantages of all endothelial keratoplasty techniques. However, because of the remaining stromal tissue and the interface, DSAEK still shows suboptimal visual acuity and relatively slow visual rehabilitation. Also, expensive equipment and a drop in donor endothelial cell density in the early postoperative period