EyeWorld Asia-Pacific December 2017 Issue

continued on page 38 December 2017 EWAP SECONDARY FEATURE 35 follow instructions and stay still during the procedure. He agreed that patient selec- tion could expand as more sur- geons in the U.S. gain experience with crosslinking. “I think there are many exciting applications for this technology,” he said. “I hope that it will gain an indication for keratitis.” Contraindicated conditions and patient types “At this point we have not been able to do any patients who re- quire IV sedation/general anes- thesia,” Dr. Garg said. “Certainly, this is a group that will greatly benefit from the procedure. I’m hoping that as the procedure be- comes shorter/more efficient, we will be able to treat these patients in the operating room with ad- equate anesthesia support.” There have been a few report- ed cases of endothelial decompen- sation with irreversible corneal edema when treating patients whose corneas are too thin, Dr. Raizman said, noting that he has treated patients with corneas as thin as 350 microns. In those cas- es, he was able to swell the cornea prior to UV light treatment, but patients with thin corneas should be warned in advance that their corneas may not swell enough for treatment, he said. Dr. Berdahl said that crosslinking is a safe procedure, and risks are low. The risk of in- fection after removing the epithe- lium is the main concern, he said, noting that he doesn’t see any strong contraindications. If the patient has a history of herpetic eye disease, it’s a little riskier. Ad- Patient undergoing epithelium-off corneal collagen crosslinking Source: Sumit “Sam” Garg, MD Views from Asia-Paci c Mahipal S. SACHDEV, MD Chairman, Medical Director, and Senior Consultant, Ophthalmology Centre for Sight B 5/24, Safdurjung Enclave, New Delhi-110029, India Tel. no. +91-9810046017 Learning from our mistakes C rosslinking has evolved over the past decade as the mainstay treatment for keratoconus. As the procedure is still in its infancy in the United States, it is imperative to learn from the mistakes already committed during the development of various modi cations and combination procedures of crosslinking. Increased intraoperative duration and postoperative pain following epithelial debridement were the two major concerns with the standard Dresden protocol. The former concern has largely been addressed with the advent of accelerated protocols based on the Bunsen-Roscoe law of reciprocity. However, it is important to recognize a lower ef cacy was demonstrated by faster protocols in vivo, with lower attening effect than the conventional approach. Thus far a 10 minute UV-A irradiation of 9 mW/cm 2 appears to provide the best balance, reducing treatment time while retaining ef cacy. A more rapid oxygen depletion during the accelerated protocol is the proposed reason for reduced ef cacy. Though a pulsed delivery appears more promising, the appropriate duration of on-off time is still a matter of controversy. Epithelial-off crosslinking continues to remain the gold standard of treatment with various studies demonstrating superiority over the transepithelial approach. An intact epithelium limits the intrastromal penetration of ribo avin. Adjunctive agents such as EDTA and BAC augment ribo avin absorption in the transepithelial approach; however, they have failed to demonstrate levels similar to epithelium- off treatment. Additionally, the epithelium consumes oxygen at a faster rate than the stroma further limiting the ef cacy. Iontophoresis has been applied as an adjunct to transepithelial delivery; however, studies validating its ef cacy vis- a-vis epithelium-off approach are required. Until further concrete evidence is obtained, the epithelium-off approach especially in pediatric eyes where the risk of progression is greater should be utilized. Various advancements have been proposed for crosslinking corneas thinner than 400 µm . Hypoosmolar ribo avin increases the distance between collagen bers due to corneal swelling. Intraoperative augmentation with the aid of a contact lens or a stromal lenticule may be more effective approaches. The concept of adapted uence is also gaining ground where the total uence is customized to the corneal thickness. Early results from the studies which are already underway are eagerly awaited. The newer iterations of crosslinking including customized treatment and PiXL for low myopia are gaining ground. Customized crosslinking delivers greater uence in the area of the cone, with subsequently lower energy outwards. The resultant differential attening helps achieve greater corneal regularization with improved visual outcomes. Early results of PiXL demonstrate a reduction in spherical equivalent of about a diopter. Supplementation of oxygen to this transepithelial approach may provide a greater degree of attening. This could potentially replace ablative procedures in suspect thinner corneas, post LASIK regression and suspicious corneal tomographies. Several studies have undoubtedly established the safety and ef cacy of topo- guided surface ablation with crosslinking. The potential to further augment the visual outcomes in combination with customized crosslinking, is an avenue that requires exploration. While we look forward to the exciting new advancements in the eld of crosslinking, it is important to progress without reinventing the wheel and to continue and abide by the basic principles that early studies from Dresden have taught us. Editors’ note: Dr. Sachdev is a consultant for Johnson & Johnson Vision (Sta. Ana, California), Zeiss (Jena, Germany), and Avedro (Waltham, Massachusetts).