EyeWorld Asia-Pacific December 2015 Issue

54 EWAP CORNEA December 2015 Views from Asia-Pacific Colin CHAN, MD Associate Professor, Vision Eye Institute and University of New South Wales Level 3 270 Victoria Avenue Chatswood, NSW, Australia Tel. no. +612 94249999 Fax no. +612 94249944 Colin.chan@vgaustralia.com D DALK is a technically challenging procedure with a steep learning curve. In this article, Dr. Rootman and Dr. Fontana provide some excellent pearls and reassurance. In particular, Dr. Rootman’s advice not to give up if you don’t achieve a big bubble the first time and that patients do well even with a more layer by layer dissection is very helpful. Like Dr. Rootman, the patients I have seen with small perforations typically still do well and a small perforation does not seem to be a definite reason to convert a DALK procedure to a PK. I agree with Dr. Fontana’s advice that surgeons should avail themselves of the excellent wetlab courses held at numerous conferences and that one less burdensome way to begin would be to attempt DALK on patients with a planned PK. Dr. Fontana also mentions intracorneal rings segments as a method of improving the keratoconic topography. I agree ring segments are a good option but I have become a lot more selective in whom I recommend for rings. One reason is that I have found that only peripheral or type 1 ectasia cones have consistently good results and the other reason is that the newer generation contact lenses are more difficult to fit over ring segments. I applaud Dr. Vinciguerra for explaining a poorly understood but crucial element of crosslinking. I have long argued that we need to better understand how to titrate the level of crosslinking for the individual patient’s needs. As Dr. Vinciguerra states, a young patient with rapidly deteriorating and aggressive keratoconus needs a greater degree of crosslinking than an older patient. Therefore an epithelium off protocol is more appropriate. Like Dr. Vinciguerra, I think further research is required to develop more customized protocols for crosslinking. Editors’ note: Dr. Chan declared no relevant financial interests. LIM Li, MD Senior Consultant and Co-Head (Clinical and Education) Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 168751 Tel. no. +65-2277255 Fax no. +65-2277290 Lim.li@snec.com.sg C rosslinking for Corneal Ectasia Currently, crosslinking procedure for corneal ectasia can be divided into conventional (30 minutes riboflavin soak and 30 minutes UVA irradiation at 3 mW/cm2 ) and accelerated (with shorter riboflavin soak time and varying shorter UVA irradiation at higher power settings, e.g., 9, 18, 30mW/cm2 ). Corneal crosslinking is usually performed with the epithelium off but recently epithelium on techniques have become available using riboflavin solutions that contain benzalkonium chloride to aid in riboflavin penetration past the epithelium. Epithelium on techniques have been shown to be less effective than epithelium off techniques with the exception of epithelium on technique combined with iontophoresis. In the future, the visual outcome after crosslinking may improve with customization of laser beam and improvement of laser nomograms. DALK for keratoconus Keratoconus is a corneal stromal disease and anterior lamellar keratopalsty allows for stromal replacement while preserving the corneal endothelium thereby significantly increasing graft survival by reducing graft attrition and allograft rejection rates. Deep anterior lamellar keratoplasty (DALK) is currently the procedure of choice for advanced keratoconus requiring keratoplasty. The Descemet’s membrane (DM) baring Anwar big bubble technique of deep lamellar keratoplasty provides better visual outcome than pre-DM techniques such as manual dissection. My preferred technique for DALK is the modified Anwar technique in which an anterior lamellar cap is removed to enable the injection of air into the deeper stromal layers of the cornea (recommended to be within 100 µm of the endothelium) which improves the chances of obtaining a big bubble. If the big bubble is not generated despite second and third attempts of air injection, I proceed to do a manual dissection of the remaining stromal layers which are already emphysematous and easier to differentiate from the DM layer. The Tan marginal dissector is a useful tool for manual dissection as it has a blunt tip to minimize perforation of the DM. Editors’ note: Dr. Lim declared no relevant financial interests. 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 experimental 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 the bubble does not form after more than one 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 surgeon] 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 DALK - from page 53