Eyeworld

83 EW FEATURE September 2015 World Cornea Congress highlights I've hydrated the anterior stroma, I'll peel it off layer by layer until I get down to Descemet's membrane and then proceed as I usually do," he said. The surgeon may potentially encounter a tear or perforation in Descemet's membrane. For a perfora- tion, Dr. Rootman said his old rule of thumb was that if he could inject air into the anterior cham- ber and if the sclera was held by Descemet's membrane, he could proceed with DALK. He is even more confident now in the technique and would possibly still proceed even with a larger tear. "I think it's important to em- phasize that you shouldn't just give up if you don't get the big bubble the first time," Dr. Rootman said. Even if you do a dissection and leave a little stroma, patients are likely to do well, he said. Learning the skills and technique for DALK is import- ant because of the possibility to help keratoconus patients avoid a rejec- tion episode or endothelial failure. You can treat a higher percentage of these patients with DALK rather than a penetrating graft, he said. the bubble does not form after more than 1 injection of air, the stroma can still be dissected. "All the stroma layers are turned white and therefore more distinguishable from the DM," he said. The localization of a deep stroma transparent layer allows the surgeon to guide the dissection up to a layer as close as possible to the DM. "In the event of a small DM perforation, stromal excision may be completed by reforming the anterior chamber with air, allowing [the sur- geon] to complete the procedure," Dr. Fontana said. If there is a large tear in the DM, a PK may be the best option. "Keratoplasty, whether PK or DALK, is indicated [when a] patient's visual acuity may not be improved using glasses or contact lenses," Dr. Fontana said. "In keratoconus a patient's ectatic cornea profile may be improved surgically by means of intracorneal ring segment implanta- tion or customized surface ablation using an excimer laser." Crosslinking for corneal ectasia Paolo Vinciguerra, MD, Milan, Italy, discussed crosslinking for the treatment of corneal ectasia. Currently, he said there are 3 main crosslinking protocols: epi-on, epi- off, and iontophoresis with epi-on. Epi-off uses 30 minutes of soaking time and a demarcation line be- tween 230 and 320 microns. Epi-on has a demarcation line between 50 and 100 microns. The iontophoresis protocol uses a demarcation line between 230 and 320 microns. The real differentiating factor is the de- marcation line, Dr. Vinciguerra said. "The demarcation line is the depth reached in the crosslinking process." The deeper and larger the percentage of tissue involved, the stronger the cornea, he said. Dr. Vinciguerra shared his general guidelines for deciding which protocol is best suited for the patient. He said that normally in the decision-making process, he would choose the standard epi-off proto- col for younger patients, or those under 18 years of age. For patients older than 45, epi-on can be a good option. He suggested iontophoresis After removal of the anterior stroma in DALK, clear Descemet's membrane remains on top of an air bubble in the anterior chamber. Source: David Rootman, MD Needle and cannula DALK Luigi Fontana, MD, Reggio Emilia, Italy, spoke on needle and cannula DALK. "DALK is more commonly performed in keratoconus patients when both glasses and contact lenses do not provide adequate correction," he said. "In these cases the DALK technique of choice is the big bubble technique as it may allow [surgeons] to bare the Descemet's membrane over a large surface area, providing a pristine graft-host interface and allowing for visual results comparable to PK." Dr. Fontana said it is easier now for surgeons to learn DALK because of the numerous meetings that offer courses, wet labs, and video resourc- es. "I would recommend practicing DALK using donor corneas not suitable for keratoplasty mounted on an artificial anterior chamber or whole globes from an animal," he said. "Most of the DALK techniques may be carried out using this exper- imental model." Additionally, he said that DALK could be attempted in the course of a planned PK for keratoconus. Dr. Fontana said that when using the big bubble technique, if with epi-on for patients older than 30. In the future, Dr. Vinciguerra ex- pects crosslinking will progress with different riboflavin concentrations, different soaking times, customized beams and more effective lasers in the periphery. He added that more advanced nomograms are needed. The crosslinking treatment var- ies depending on the disease being treated, whether it's keratoconus or other ectatic conditions. In other ectatic disorders (not keratoconus), Dr. Vinciguerra said the deepest pos- sible demarcation line is needed to be effective, which can be achieved with epi-off and a long soaking time. The laser is not as effective for many reasons on the corneal periphery for focusing and beam energy densi- ty. "So we should focus [on the] periphery and offset the laser beam inferiorly," he said. EW Editors' note: Drs. Fontana and Rootman have no financial interests re- lated to this article. Dr. Vinciguerra has financial interests with Nidek (Fremont, Calif.), Oculus (Arlington, Wash.), and Schwind eye-tech solutions (Kleinostheim, Germany). Contact information Fontana: luifonta@gmail.com Rootman: d.rootman@utoronto.ca Vinciguerra: paolo.vinciguerra@humanitas.it AT A GLANCE • DALK may be used for keratoconus patients when glasses and/or contact lenses do not provide the necessary correction. • If a surgeon is not able to generate a big bubble on the first attempt, he or she should not give up. Surgeons may be able to do so on another attempt but should be cautious in dissecting, especially if working with a type 2 bubble instead of type 1. • The demarcation line reached in the crosslinking process is important because the deeper and larger the percentage of tissue involved, the stronger the cornea.

• Cover