Eyeworld

EW CORNEA 86 August 2017 6. Chen S, et al. Epithelium-on corneal collagen crosslinking for management of ad- vanced keratoconus. J Cataract Refract Surg. 2016;42:738–49. 7. Lombardo M, et al. Randomized con- trolled trial comparing transepithelial corneal cross-linking using iontophoresis with the Dresden protocol in progressive keratoconus. Ophthalmology. 2017;124:804–12. 8. Lombardo M, et al. Biomechanical changes in the human cornea after transepithelial corneal crosslinking using iontophoresis. J Cataract Refract Surg. 2014;40:1706–15. 9. Mastropasqua L, et al. Structural modifi- cations and tissue response after standard epi-off and iontophoretic corneal crosslinking with different irradiation procedures. Invest Ophthalmol Vis Sci. 2014;55:2526–33. 10. Bikbova G, et al. Standard corneal collagen crosslinking versus transepithelial iontophore- sis-assisted corneal crosslinking, 24 months follow-up: randomized control trial. Acta Ophthalmol. 2016;94:e600–e606. 11. Vinciguerra P, et al. Transepithelial iontophoresis corneal collagen cross-linking for progressive keratoconus: initial clinical outcomes. J Refract Surg. 2014;30:746–53. 12. Lombardo M, et al. Novel technique of transepithelial corneal cross-linking using iontophoresis in progressive keratoconus. J Ophthalmol. 2016;2016:7472542. Editors' note: Dr. Lombardo has no financial interests related to his comments. Contact information Lombardo: mlombardo@visioeng.it 0.03 ± 0.10 logMAR—compared to 0.06 ± 0.10 logMAR at baseline to 0.03 ± 0.09 logMAR at 12 months in the control group. Manifest spheri- cal equivalent refraction changed by +0.71 ± 1.44 D in the T-ionto group and +0.21 ± 0.76 D in the control group. Dr. Lombardo said leaving the epithelium intact might have the benefit of not irradiating the most anterior portion of the stroma di- rectly. "This may have an important effect on manipulating the mechan- ical integrity of the anterior cornea and also the optical properties of the anterior cornea, which are the most important for changing the refrac- tive properties of the eye," he said. A previously published study involving transepithelial ionto- phoresis crosslinking also noted improved CDVA at 1 year postop in addition to halted progression of keratoconus. 11 Dr. Lombardo said in compar- ison to some other iontophoresis crosslinking studies, this study saw better results, which he credited to the removal of the mucin layer prior to the iontophoretic process. 12 "I remove this electronegative pre-corneal mucin layer in order to increase the movement of the ribo- flavin-phosphate into the stroma during iontophoresis. If I can further improve the penetration of ribofla- vin into the stroma, I think we can further improve the clinical results," he said. In fact, Dr. Lombardo said his team is working on a new technol- ogy that can measure the riboflavin concentration in the human cornea to theoretically customize the treat- ment to each patient's eye. "We have correlated the riboflavin concentration in the stroma during treatment with an increased stiffness of the stroma," Dr. Lombardo said. "We know we need to go over a threshold of riboflavin during irradiation and in order to generate additional corneal crosslinking in the stroma. We now have an understanding of which are the best riboflavin concentrations to enter the stroma." Overall, the investigators found their method of iontophoresis-as- sisted, epi-on crosslinking improved keratometry readings in 80% of cases and saw stable or improved uncorrected distance visual acuity and CDVA in 100% of cases along with a decrease in myopic defocus in 60% of cases. Standard crosslinking, in contrast, improved Kmax values in 90% of cases but only reduced myopic defocus in 33% of cases. The main limit of the T-ionto protocol, Dr. Lombardo said, was seen in patients younger than 24 years old, where it was significant- ly less effective than the Dresden protocol. "My recommendation is to keep using the gold standard in pediatric patients and those patients young- er than 24 years old. Probably this is because at this age keratoconus progression is more aggressive, and it's likely biomechanical strengthen- ing is not as effective as in the gold standard," he said. The researchers stated that further comparative studies with larger data sets and longer follow-up periods are needed to validate this epi-on technique. EW References 1. Rush SW, et al. Epithelium-off versus transepithelial corneal collagen crosslinking for progressive corneal ectasia: a ran- domised and controlled trial. Br J Ophthalmol. 2017;101:503–08. 2. Cerman E, et al. Transepithelial versus epithelium-off crosslinking in adults with progressive keratoconus. J Cataract Refract Surg. 2015;41:1416–25. 3. Shalchi Z, et al. Safety and efficacy of epithelium removal and transepithelial corneal collagen crosslinking for keratoconus. Eye (Lond). 2015;29:15–29. 4. Nawaz S, et al. Trans-epithelial versus conventional corneal collagen crosslinking: A randomized trial in keratoconus. Oman J Ophthalmol. 2015;8:9–13. 5. Spadea L, et al. Recovery of corneal sensitivity after collagen crosslinking with and without epithelial debridement in eyes with keratoconus. J Cataract Refract Surg. 2015;41:527–32. Study continued from page 84 Crosslinked corneal tissue Crosslinking procedure Source (all): Phoebe Lenhart, MD

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