Eyeworld

EW FEATURE 80 Update on crosslinking • September 2017 Refractive continued from page 78 possibility of PiXL for presbyopic correction. Dr. Dupps agreed that early trials of refractive crosslink- ing are encouraging, and he thinks that enhancing the predictability of refractive crosslinking is the next critical step in moving the concept forward. "By building on advances in crosslinking science to enhance and more tightly control the stiffening effect, other personalization tools such as corneal tomography, emerg- ing biomechanical measurement technologies, and simulation-based planning tools can help leverage our predictive capabilities toward more personalized treatments," he said. EW References 1. Roy AS, et al. Patient-specific computational modeling of keratoconus progression and dif- ferential responses to collagen cross-linking. Invest Ophthalmol Vis Sci. 2011;52:9174–87. 2. Seiler TG, et al. Customized corneal cross-linking: One-year results. Am J Ophthal- mol. 2016;166:14–21. 3. Cassagne M, et al. Customized topogra- phy-guided corneal collagen cross-linking for keratoconus. J Refract Surg. 2017;33:290–97. 4. Scarcelli G, et al. Biomechanical character- ization of keratoconus corneas ex vivo with Brillouin microscopy. Invest Ophthalmol Vis Sci. 2014;55:4490–5. 5. Tomita M. Combined laser in-situ keratomil- eusis and accelerated corneal crosslinking: an update. Curr Opin Ophthalmol. 2016;27:304– 10. 6. Kanellopoulos AJ, et al. Topography-guided hyperopic LASIK with and without high irra- diance collagen cross-linking: initial compar- ative clinical findings in a contralateral eye study of 34 consecutive patients. J Refract Surg. 2012;28:S837–40. 7. Seiler TG, et al. Superficial corneal cross- linking during laser in situ keratomileusis. J Cataract Refract Surg. 2015;41:2165–70. 8. Elling M, et al. Photorefractive intrastro- mal corneal crosslinking for the treatment of myopic refractive errors: Six-month interim findings. J Cataract Refract Surg. 2017;43:789–795. Editors' note: Dr. Dupps has finan- cial interests with Avedro, OptoQuest (Cleveland), and Carl Zeiss Med- itec (Jena, Germany). Dr. Elling has financial interests with Avedro. Avedro supports Dr. Behndig's ongoing study on PiXL with an unrestricted grant. Contact information Behndig: anders.behndig@umu.se Dupps: bjdupps@sbcglobal.net Elling: Matthias.Elling@kk-bochum.de and the LASIK Xtra model, suggest- ing that mild crosslinking effects wouldn't have an impact on nomo- grams. Protection against ectasia was Dr. Elling and his group perform epi-on refractive crosslinking (PiXL) with an oxygen supply to boost its effect. The patient wears special oxygen goggles, and in the epithelial prep stage, a riboflavin soaked sponge is applied to the treatment area before starting riboflavin drops. This procedure uses a pulsed ultraviolet light. Source: Matthias Elling, MD a harder question to answer because it's a rare condition that would require long-term follow-up to assess the risk. "In the modeling exercise, we saw that if you stiffen that bed it does give the cornea more resistance to shape change," he said, adding later that the most compelling argument for LASIK plus crosslink- ing he's seen is by Kanellopoulos et al. in hyperopic eyes. 6 This study showed the crosslinking LASIK group had less hyperopic regression over the year follow-up and better refractive outcomes. Correcting refractive error Another avenue for crosslinking is correcting refractive error. Photo- refractive intrastromal crosslink- ing (PiXL) is in clinical trials with Avedro's Mosaic system to provide topography-guided accelerated crosslinking to correct low levels of refractive error. "Our experience with PiXL for low myopia has been very positive," Dr. Elling said. "We have been per- forming epithelium-off PiXL since 2014, and since last year, we began offering epi-on treatments with supplemental oxygen. Our patients are very satisfied with the vision improvement, and the idea of a minimally invasive procedure is very appealing. In our clinical studies, we had the possibility to show that we are able to reach a refractive change with PiXL." Dr. Elling added that this technique hasn't shown itself to be as precise as LASIK or PRK. 8 Referencing a company-spon- sored trial with 1-year follow-up, Dr. Elling noted statistically signifi- cant improvements in mean man- ifest sphere at all follow-up visits compared to baseline with a mean change of about 1 D. This reduction remained stable. "Given its noninvasive nature, PiXL presents a potential treatment option for patients with low my- opia who require a less invasive refractive correction procedure than conventional laser vision correction. In comparison to LASIK or PRK we have no tissue ablation. In the fu- ture, PiXL may give us the possibili- ty … for refractive adjustments after cataract surgery, to treat irregular astigmatism, or even to do a touch- up after LASIK with thin residual stromal bed," Dr. Elling said, adding that they are currently evaluating techniques to balance adequate epithelial disruption and postop comfort. Dr. Behndig said results with PiXL have shown stable and "suffi- ciently consistent" results. Going forward, both Drs. Behndig and Elling mentioned the

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