Eyeworld

EW FEATURE 50 Crosslinking playbook • January 2019 AT A GLANCE • Crosslinking (CXL) is the only therapy indicated to slow the progression of ectasia, which if left uncontrolled may necessitate corneal transplantation. • Research is expanding indications of CXL to include refractive applica- tions and corneal infections, while exploring potential substitutions to the components of the procedure. • Stem cells may change the para- digm of treatment by facilitating stromal regeneration. • Doctors are divided on Bowman's layer transplantation, a complicated procedure with a steep learning curve that has the advantages of an acellular graft and sutureless tech- nique that may arrest progression of ectasia. by Chiles Aedam R. Samaniego EyeWorld Asia-Pacific Senior Staff Writer said. "We make most of our daily decisions based on topographic and tomographic data from a Pentacam system [Oculus, Wetzlar, Germany]." While corneal tomographers do not assess true biomechanics, they provide morphologic information on curvature and elevation that can be used to assess disease severity and localization. Meanwhile, devices such as the Corvis ST (Oculus) and Ocular Response Analyzer (Reichert Technologies, Depew, New York) derive additional data on biome- chanical strength from the cornea's dynamic response to an air puff, representing a more comprehensive picture of the state of the cornea. In terms of research, Dr. Thompson noted that Brillouin spectroscopy and OCT biomechan- ical assessment may provide better tools for mapping the strength of the cornea in three dimensions. Dr. Alió emphasized the value of biomechanics measuring devices in research, noting that "the cost benefit of their use is negative for the practical clinician." This does not devalue their application in clinical research, but in practice, "you do not need them for good treatment of keratoconus." Epi-on Research on epi-on protocols high- lights the role of oxygen in CXL. "Recent studies have shown that oxygen plays a key role in regulat- ing the amount of crosslinking that we can induce, particularly when other techniques (for example, Intacs [Addition Technology, Lom- bard, Illinois], DALK, or Bowman's layer transplantation) may be supe- rior options," he said. Dr. Alió, often cited for his research on the topic, detailed his approach to CXL. "I use CXL in my practice in all keratoconus that is suspicious of evolution, either demonstrated by objective methods or if the patient is under 30," he said. "In patients over 40, I make a follow-up observation of the case, even though more and more I think that we should do crosslinking in these patients, especially if they have a decrease in best corrected visual acuity." Dr. Alió follows the Dresden protocol for clearly progressing keratoconus or in the high-risk age group but performs epi-on in patients over 35 in whom progres- sion is doubtful or who may have problems with follow-up. "I per- form epi-on crosslinking making [a] few scratches in the epithelium to enhance the penetration of ribo- flavin," he added. "This increases the penetration of the riboflavin and increases the effect of the UV light to the superficial 150 microns stroma, which seems to be sufficient in many patients to have the effect." Evaluating biomechanics The clinical evaluation of corneal biomechanics is currently lacking. "Accurate measurement of corne- al biomechanics in a real world clinical environment remains a challenge today," Dr. Thompson and if not controlled, it may result in corneal transplantation," he said. Despite being first described more than 20 years ago, "crosslink- ing continues to generate a tremen- dous amount of research interest around the world," Dr. Thompson added. EyeWorld corresponded with Dr. Thompson, as well as Jack Parker, MD, PhD, Parker Cornea, Birmingham, Alabama, and Jorge Alió, MD, professor and chairman of ophthalmology, University of Al- icante, Spain, to find out where this research is taking the procedure. In practice While Dr. Thompson performs epi- off CXL for patients with progres- sive keratoconus and corneal ectasia using the Avedro KXL device with the Photrexa riboflavin formula- tions, the practice is also participat- ing in an Avedro-sponsored Phase 3 clinical trial to evaluate an approach to epithelium-on CXL. "Optimi- zation of epi-on protocols for the treatment of keratoconus is an espe- cially hot topic today," he said. Dr. Parker (together with John Parker, MD) operates the Kerato- conus Center of Alabama, hence, CXL is "an indispensable part of our practice," he said. "It's useful not only for our keratoconic patients with documented progression, but also for individuals with pellucid marginal degeneration and post- LASIK ectasia." However, Dr. Parker said that the procedure might only be effec- tive in mild to moderate disease. "In patients with more severe ectasia, Ophthalmologists look ahead at the future of crosslinking A ccording to Vance Thompson, MD, Vance Thompson Vision, Sioux Falls, South Dakota, "Crosslinking [CXL] with the Avedro KXL device [Waltham, Massachusetts] is the only FDA ap- proved therapy to slow the progres- sion of ectasia. "Progression results in reduc- tion of visual acuity that becomes increasingly difficult to manage with scleral or specialty contact lenses, Future directions of CXL continued on page 52

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