EyeWorld India December 2017 Issue

Surgeons continue to debate this issue because there are pros and cons to both techniques I n recent years, there has been much debate over the protocol for corneal colla- gen crosslinking. In 2003, the Dresden protocol established epi-off crosslinking as the gold standard, and epi-off crosslinking was approved by the U.S. Food and Drug Administration in April 2016. Using this method, the epithelium is removed prior to soaking the cornea in a riboflavin solution and exposing it to ultra- violet light. The results have been good, but the technique is not ideal. Because part of the epithe- lium is scraped off, there is a risk of infection and side effects, such as corneal haze. More recently, ophthalmolo- gists have begun to consider whether the epithelium needs to be removed. Leaving the epithe- lium intact would make the pro- cedure less invasive and less time consuming. There are advantages and dis- advantages to both methods. In the less invasive epi-on method, patients experience less pain and faster recovery, but there is the risk of progression. In contrast, with the epi-off approach, the epi- thelium is removed to get quicker, deeper saturation of the ribofla- vin, which may be more effective, but there is the risk of infection. Epi-off Epi-off is the traditional method for corneal collagen crosslink- ing, and Matthias Elling, MD, Bochum, Germany, thinks it is the best, most effective choice for patients. “In Germany, we have had access to both the epi-off and epi-on approaches for many years. Today, we use an epi-off approach for most of our keratoconus pa- tients because we are confident that it will be effective in stabiliz- ing progression. There is much interest in the epi-on treatment as a gentler method, but for a patient with keratoconus, progression means worsening vision, and we want to offer our patients the best chance to preserve visual func- tion. Epi-off is the established standard of care, and both our personal experience and the peer- reviewed literature provide strong support for the efficacy of the epi- off approach,” Dr. Elling said. A recent European review noted that almost all published long-term data and comparative studies have been performed with the epi-off technique. 1 Epi-on studies suggest some efficacy, but less than with epi-off treatments, and long-term data are unavail- able. “Although the epi-on ap- proach has seen spikes in popu- larity over the years as new riboflavin formulations have been released, these approaches have not been validated in the peer-reviewed literature. 2 What we see in the scientific literature is that riboflavin is only one part of the equation and that the epithelium also acts as a barrier to sufficient availability of UVA light and oxygen,” Dr. Elling said. “Recently, we have been evaluating new technology from Avedro [Waltham, Massachusetts] aimed at addressing these limita- tions, which includes specialized riboflavin formulations and the delivery of supplemental oxygen to the stroma using oxygen gog- gles. It’s very exciting research and is important for the refractive applications of crosslinking, such as the PiXL procedure.” 3 He noted that the epi-off method has been firmly estab- lished to be both safe and effec- tive and is the global standard of care for the treatment of progres- sive keratoconus. “In patients with progressive disease, discom- fort associated with removal of the epithelium is far outweighed by maximizing the potential to preserve visual function. Patients may come into the hospital with an idea of which procedure is preferable, but in the end, it is our responsibility to provide the procedure that is best for their long-term disease prognosis. The peer-reviewed literature suggests that there are greater rates of pro- gression with currently studied epi-on techniques,” he said. Epi-on Doyle Stulting, MD, PhD , Atlanta, is a strong proponent of the epi-on method. He be- gan performing crosslinking in 2008 using the classical Dresden technique. “The data we pro- duced from the study in 2008 went toward obtaining approval for Avedro for that technique. We also ran a clinical trial for Top- con [Tokyo, Japan] with a similar protocol,” he said. In October 2013, Dr. Stulting began working with a protocol devised by CXL-USA, which is a physician-sponsored, prospective research effort underway at 13 sites across the country. The CXL- USA protocol gives the surgeon the freedom to choose the epi-on or epi-off technique, and most of the investigators in CXL-USA choose epi-on. “Epi-on is all I have done since October 2013. With that protocol, we have been obtaining results that are equal to or better than what has been ob- tained with the epi-off protocol, the classical Dresden protocol, in our hands and in others. We are preparing those data for publica- tion,” Dr. Stulting said. He has observed better ri- boflavin penetration and better riboflavin concentrations in the stroma using the epi-on proto- continued on page 40 September 2017 Dec EWAP SECONDARY FEATURE 39 Corneal collagen crosslinking: Is epi-off or epi-on best for patients? by Michelle Stephenson EyeWorld Contributing Writer AT A GLANCE • There are advantages and disadvantages to both epi-on and epi-off corneal collagen crosslinking. • In the less invasive epi-on method, the cornea’s epithelial layer is left intact. Patients experience less pain and faster recovery. • With the epi-off approach, the epithelium is removed to get quicker, deeper saturation of the ribo avin.