Eyeworld

EW FEATURE 82 Corneal collagen crosslinking • September 2016 Dr. Elbaz said using a local anes- thetic to disrupt epithelial integrity can also help improve penetrance of Ricolin (Carleton Optical, Buck- inghamshire, U.K.), a 1% riboflavin solution with enhancers. Even still, Dr. Elbaz said better solutions for the efficacy of epi- on need to emerge before many ophthalmologists choose to convert from epi-off. Epi-off crosslinking continues to evolve outside of the Dresden proto- col as well. Dr. Graue-Hernandez said his team has been using an accelerat- ed crosslinking protocol for the last 4 years. This protocol increases UVA energy delivered to the eye but reduc- es the exposure time significantly. He said a "pulse" technique could be beneficial as well. "Theoretically, oxygen is needed for the reaction to occur. Whenever you use continuous illumination, oxygen is deprived and reaction is less," Dr. Graue-Hernandez said. "There have been a few trials and a few in vivo experiments with pulse therapy. We don't have it but you can buy a system that increases the oxygen concentration on the eye. There is a little patch that is plugged into an oxygen device that pumps 90% oxygen into an environment right in front of the eye. That's used in combination with a pulse therapy to increase the reaction." Overall, Dr. Garg said the cur- rent atmosphere of crosslinking is "very exciting." "I do think that with time our treatments will evolve and perhaps we will have an epi-on treatment that will provide efficacy on par with epi-off treatments with im- proved safety and patient experi- ence," Dr. Garg said. "My take-home message is that we need to continue improving the epi-on technique so the efficacy will be at least equivalent to the epi-off technique. Until then, the epi-on technique should be reserved only for rare cases where, for example, a general anesthesia procedure is contraindicated in a child with pro- gressive keratoconus, knowing that a retreatment may be needed in the future," Dr. Elbaz said. "Otherwise, the vast majority of patient should receive the epi-off crosslinking." EW References 1. Wollensak G, et al. Riboflavin/ultraviolet -a-induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol. 2003;135:620–7. 2. Cummings AB, et al. Newer protocols and future in collagen cross-linking. Indian J Ophthalmol. 2013;61:425–7. 3. Rossi S, et al. Standard versus trans-epi- thelial collagen cross-linking in keratoconus patients suitable for standard collagen cross-linking. Clin Ophthalmol. 2015;9:503–9. 4. Spadea L. Recovery of corneal sensitivity after collagen crosslinking with and without epithelial debridement in eyes with keratoco- nus. J Cataract Refract Surg. 2015;41:527– 32. 5. Caporossi A, et al. Transepithelial corneal collagen crosslinking for progressive kerato- conus: 24-month clinical results. J Cataract Refract Surg. 2013;39:1157–63. 6. Soeters N, et al. Transepithelial versus epithelium-off corneal cross-linking for the treatment of progressive keratoconus: a randomized controlled trial. Am J Ophthalmol. 2015;159:821–8. 7. Eraslan M, et al. Efficacy of epithelium -off and epithelium-on corneal collagen cross-linking in pediatric keratoconus. Eye Contact Lens. 2016 Feb 29. [Epub ahead of print]. 8. Hashemi H, et al. Evaluation of the pro- phylactic use of mitomycin-C to inhibit haze formation after photorefractive keratectomy in high myopia: a prospective clinical study. BMC Ophthalmol. 2004;4:12. Editors' note: The physicians have no financial interests related to their comments. Contact information Elbaz: urielbaz@gmail.com Garg: gargs@uci.edu Graue-Hernandez: egraueh@gmail.com While research has shown mito- mycin-C (MMC) can prevent corneal haze after photorefractive keratec- tomy (PRK), 8 Dr. Graue-Hernandez doesn't use MMC in crosslinking, calling the haze caused by this procedure different than that seen post-refractive surgery. Dr. Garg also does not use MMC. Standard postop care involves a course of antibiotics and topical ste- roids, although Dr. Graue-Hernandez said the steroid use might be longer for epi-off patients as there is more inflammation. Dr. Garg said he treats crosslinking patients as he would a PRK patient with topical steroid taper and aggressive preservative-free artificial tears. Improving epi-on and enhancing epi-off One way to possibly advance per- formance of the epi-on technique would be to improve riboflavin penetration into the corneal stroma. Several companies have developed riboflavin solutions that include "enhancers" for this purpose. "There are several reported ad- ditives to increase the permeability of riboflavin through the epithelium into the stroma: BAK, tetracaine, surfactants, tris hydroxymethyl ami- nomethane, and/or sodium EDTA," Dr. Garg said. debatable, and there is significant- ly more risk of progression with epi-on, but that doesn't mean it doesn't work in good patients. That means you have to choose the right patient," Dr. Graue-Hernandez said, explaining that epi-on patients should be informed of the risk of progression and be carefully moni- tored postop. Considering the risk-benefit ratio Epi-on might take less time and come with less pain, a quicker recovery, and less risk for infection, but continued progression might be looming. Epi-off, on the other hand, is a longer, more painful procedure with greater risk for infection and other side effects such as corneal haze, but with the stronger like- lihood of stopping keratoconus progression. "Complications have been reported for both techniques," said Sumit "Sam" Garg, MD, Gavin Herbert Eye Institute, University of California, Irvine, who performed epi-off crosslinking as part of an Avedro (Waltham, Massachusetts)- sponsored accelerated treatment protocol study. "It is important to follow these patients closely and to educate your patients about signs that may be harbingers to serious complications." Epi-off continued from page 80

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