Eyeworld

EW CORNEA 84 August 2017 by Liz Hillman EyeWorld Staff Writer the Dresden protocol of soaking the eye with a riboflavin solution takes 30 minutes. Decreasing the soaking time from upward of 30 minutes to just 5 is an advantage for the patient and the physician, Dr. Lombardo said. He acknowledged that there is a bit of suction on the cornea during iontophoresis with the electrode, but patient discomfort in the process is uncommon. In the study, 34 eyes of 25 patients were randomized to receive either T-ionto crosslinking (22 eyes of 20 patients) or the Dresden pro- tocol (12 eyes of 10 patients) with a 12-month follow-up period. In terms of corneal topography, the average Kmax decrease was –0.52 ± 1.30 D and –0.82 ± 1.20 D in the T-ionto and Dresden protocol groups, respectively. A flattening effect of more than –0.5 D occurred in 50% of the T-ionto eyes and 66% of the Dresden protocol eyes. Con- versely, a steepening of more than 0.5 D occurred in 8% of T-ionto eyes and 5% of control eyes. "Comparing the changes in Kmax from baseline between groups revealed no statistically significant differences at 12 months," Lombardo et al. wrote. In terms of the visual improve- ments, the study authors wrote that significant improvements in correct- ed distance visual acuity (CDVA) and manifest refraction were observed in the T-ionto group. Although there was no significant difference in CDVA at baseline between the two groups, CDVA improved significant- ly in the T-ionto group at 12 months of follow-up—from 0.12 ± 0.20 to manner that was "almost compa- rable to that of standard crosslink- ing." 8 Other research involving T-ionto CL has found it to result in less tissue damage than the Dresden protocol and other epi-on techniques. Although it was less effective than standard crosslinking at 24 months postop, it did achieve the goal of stopping keratoconus progression. 9–10 Dr. Lombardo said in this study, investigators used a dextran-free, phosphate-enriched riboflavin solution (0.14% riboflavin-5-phos- phate hypotonic solution with ethylenediaminetetraacetic acid and trometamol), which a commercial- ly available iontophoresis device helped to penetrate through the epithelium into the stroma. "The mechanism of action of iontophoresis is to generate a very low electricity around the cornea in order to move these ions into the corneal tissue. We applied a cur- rent voltage and let the negatively charged phosphate-enriched ribofla- vin enter the stroma," Dr. Lombardo explained. Dr. Lombardo said the ion- tophoresis process of riboflavin loading takes only 5 minutes, while found that iontophoresis-assisted transepithelial crosslinking was as effective as the Dresden protocol in terms of stabilizing the cornea in adults older than 24 years old. "We were well aware of the efficacy of iontophoresis improv- ing the biomechanical stability of the cornea," Dr. Lombardo said, noting several years of laboratory validation. But in some ways "the results we found in the clinical study went beyond our expectations. For example, I recorded a significant visual improvement in most of the patients and also a decrease in the myopic spherical equivalent refrac- tion, which has never been recorded before in either the gold standard protocol or former transepithelial protocols using dextran-enriched riboflavin solutions." Dr. Lombardo and his colleagues have been researching transepithe- lial corneal crosslinking using ion- tophoresis (T-ionto CL) for several years. In 2014, Dr. Lombardo and fellow investigators published the results of T-ionto CL on four human donor eye globes, finding that this technique increased biomechanical strength of the corneal tissue in a Using an electrical charge to drive riboflavin deeper into the corneal layers resulted in biomechanical strengthening and several other promising factors E pithelium-on (also called transepithelial) corne- al crosslinking has been shown repeatedly to not be quite as effective as the standard epithelium-off Dresden protocol as treatment for progressive keratoconus and corneal ectasia. 1–3 However, the benefits of epi-on crosslinking—increased patient com- fort, a better healing response, and less risk for haze or corneal ulcers— and promising results (even when shown to be less effective than the epi-off protocol) continue to drive researchers to investigate techniques to improve the ability for riboflavin to penetrate through the epithelium into the stroma and enhance the crosslinking effects that occur upon UVA irradiation. 4–6 One such technique—iontopho- resis—uses a low-voltage electrical current to drive the riboflavin effi- ciently and deeper into the corneal layers. Epi-on crosslinking using iontophoresis has been researched before with encouraging results, but a recently published randomized controlled trial that compared tran- sepithelial crosslinking using ionto- phoresis with the Dresden protocol in progressive keratoconus patients yielded several interesting results. 7 The research, led by Marco Lombardo, MD, PhD, Rome, Italy, Study compares standard crosslinking protocol to iontophoresis-assisted epi-on technique " The results we found in the clinical study went beyond our expectations. " —Marco Lombardo, MD, PhD continued on page 86 Research highlight the laboratory and it has great prom- ise, but it's not there yet." Synthetic collagen material used as a corneal substrate—just stroma, not endothelium or epithelium—has shown some promise in previous research. "However, the problem with that is it is not a strong materi- al," Dr. Akpek said. "You can only replace the stroma part, which wouldn't work so well because the need is not there." Dr. Aquavella is more optimistic about the collagen approach and noted research continues on improv- ing it. "They are getting better at it, but it's not here yet," Dr. Aquavella said. Another approach that has generated some interest among re- searchers is the use of stem cells on the ocular surface. The approach has been able to reduce the incidence of corneal melting and ulcers, but the stem cells are often transplanted from other patients so recipients face the prospect of requiring anti- rejection drugs for the rest of their lives, Dr. Aquavella said. EW Editors' note: Drs. Akpek and Aquavella have no financial interests related to their comments. Contact information Akpek: esakpek@jhmi.edu Aquavella: James_Aquavella@URMC.Rochester.edu Artificial continued from page 83

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