EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/407647
39 EW REFRACTIVE SURGERY November 2014 Contact information Lin: tclin@shaw.ca Stein: rstein@bochner.com have been exploring both combined and consecutive crosslinking and ab- lation procedures, but seem to trend toward performing a combined procedure. Because both procedures require removal of the corneal epithelium, it makes sense to do them simulta- neously, Drs. Lin and Stein said. A combined surgery is easier on the patient and also saves valuable OR time. Pearls for getting started Topography-guided laser systems base their measurements on Placido disc topography, Scheimpflug imag- ing, or a combination of the two. In September 2013, the FDA approved two excimer lasers with topogra- phy-guided ablation software—the WaveLight ALLEGRETTO WAVE EyeQ (Alcon, Fort Worth, Texas) and the NAVEX Quest EC-5000 (Nidek, Fremont, Calif.). Both systems use Placido disc-based topography and proprietary software to customize the tissue ablations. Every laser imaging system is different, so Dr. Lin stressed the need to understand the laser that you are using. The best thing to do, he said, is to look at what a pure topography-guided treatment would do—based on the topography mea- surements, set the refraction to zero and observe whether it is inducing myopia or hyperopia. It is also important to estab- lish proper patient expectations, Dr. Stein said. Make sure that the patient understands that the goal of a topographic ablation is to improve best spectacle corrected visual acuity and not best uncorrected visual acuity, he said. He recommended starting out with keratoconus eyes in which the dioptric difference across the cornea is less than 10 D. Corneas should be relatively clear without scarring and have a satisfactory corneal thickness of at least 450 µm, he added. "Use a PTK mode to remove the corneal epithelium set at 50 µm with a 9 mm optical zone," he said. "This is followed by the topography- guided PRK treatment, which should generally be limited to 50 µm. My preference is to use large optical zones of 6.5 mm or 6.0 mm." Dr. Stein uses a balanced salt solution frozen "popsicle" at the end of the laser ablation for 10 to 20 seconds as he does with all PRK treatments, to enhance postop comfort. He also routinely uses a pledget of mitomycin-C to decrease the risk of corneal haze. EW Editors' note: Drs. Lin and Stein have no financial interests related to their comments. Ordering information: IOP Ophthalmics (800) 535-3545 Product Number: 68330 Product description: ½ Cornea with Scleral Rim *68329 Product description: 1∕ ³ Cornea with Scleral Rim *not all grafts may be available in your market /area 8100 R0 05/15/14 Tutoplast is a registered trademark of Tutogen Medical, GmbH 30 Days Stunning Results! 7 Days 1 Day Photos courtesy of N. Douglas Baker, MD placement of a clear cornea patch graft during glaucoma tube shunt surgery We are pleased to announce the addition of clear cornea tissue to our line of ophthalmic patch grafts. This tissue is processed to the same rigorous standards as our other Tutoplast® processed grafts with the added benefit that only clear corneal tissue can bring. Why Clear Cornea from IOP? Safety • 3,000,000+ implants sterilized through the Tutoplast® tissue sterilization process with zero incidence of implant associated infection. • The Tutoplast® tissue sterilization process including low dose gamma irradiation achieves 10 - 6 sterility assurance level. Flexibility • Clear cornea tissue is supplied with sclera rim in ½ & ¹⁄ ³ configurations. • 5 year shelf life at room temperature. No special shipping or refrigeration required. Aesthetics • Clear cornea can be used for inferior or exposed placement when an translucent outcome is desired.