Eyeworld

EW FEATURE 80 Corneal collagen crosslinking • September 2016 AT A GLANCE • Discussion continues on whether —and when—epi-on crosslinking should be done. • Epi-on and epi-off treatments each present their own set of pros and cons. • Experts advise strict patient selection for epi-on procedures, noting efficacy concerns compared to epi-off. by Liz Hillman EyeWorld Staff Writer most of the time he performs epi-off procedures. Young patients who might not be as tolerant of pain and who have limited progression of the disease make better epi-on candidates, Dr. Graue-Hernandez said. Those who have had significant progression within 6 months to a year, however, fare better with epi-off treatment. "We know the biomechani- cal effect for epi-on treatment is reduced, but the clinical results can be the same in the long run," he said. "Epi-off has a greater amount of biomechanical effect. We know the demarcation line is deeper, and therefore we think that the biome- chanical strengthening of the cornea is greater." Should a patient receive epi-on treatment and experience progres- sion, Dr. Graue-Hernandez said epi- off can still be performed. "The evidence in favor of doing epi-off is strong and it's not refutable. The evidence of epi-on is spare general anesthesia and save OR time," Dr. Elbaz said. "On the other hand, the epi-off procedure may result in persistent epithelial defect, haze, and corneal ulcer, although the risk for these complications is quite low." Dr. Elbaz said he only performs epi-off procedures on his patients, calling it "more efficient in arrest- ing the progression of keratoconus" with "minimal" risk. Picking the right protocol for the patient Enrique Graue-Hernandez, MD, Institute of Ophthalmology Conde de Valenciana, Mexico City, agreed that the data for epi-on crosslinking is not as strong as that available for epi-off, but "that doesn't mean that epi-on doesn't work," he added. "I think there are good patients for both treatments. There are certain conditions that may cause me to do epi-on or epi-off," Dr. Graue-Hernandez said, noting that of transepithelial (epi-on) crosslink- ing, which leaves the epithelium intact, but requires the riboflavin to sit (or load) on the eye longer. Recent studies that have com- pared epi-on vs. epi-off crosslinking have found that both protocols improve corrected and uncorrect- ed distance visual acuity. 3 Other research found that both protocols might cause hypoesthesia, but all patients recovered completely re- gardless of the protocol taken. 4 The researchers found hypoesthesia was more pronounced in epi-off cases and recovery was shorter for epi-on cases though. Uri Elbaz, MD, Department of Ophthalmology, Rabin Medical Center, Tel Aviv University, Tel Aviv, Israel, cited other research that sug- gests "evidence for epi-on [crosslink- ing] efficacy is weak," he said. 5–7 "Obviously, there are numerous advantages for the epi-on proce- dure, including patient comfort, throughput, fast recovery with less work. Also, the epi-on procedure can Deciding when to deviate from standard crosslinking protocol, if at all, comes down to careful patient selection T o scrape or not to scrape? That is the question. Removal of the epithe- lium prior to soaking the cornea in a riboflavin solu- tion and exposing it to ultraviolet light is the standard protocol to cre- ate new collagen bonds and stabilize ectatic corneas, such as in patients with progressive keratoconus. But some say the epithelium does not need to be removed to achieve this stabilizing effect with the benefit of reducing patient discomfort, proce- dure time, and risk of infection. Traditional epi-off crosslinking on human subjects—the Dresden protocol—was first described in the American Journal of Ophthalmology in 2003 by Gregor Wollensak, MD, Eberhard Spoerl, MD, and Theo Seiler, MD. 1 This study described the technique of scraping off keratoco- nus patients' epithelium, soaking their eyes in a riboflavin solution, and exposing their eyes to UVA light at 1-cm distance for 30 minutes. It stopped progression in all 22 patients. Since then, several different iterations of crosslinking protocols to treat progressive keratoconus and ectasia have emerged in the hope of improving safety and efficacy. 2 Perhaps one of the most dis- cussed alternative protocols to the traditional Dresden protocol is that Epi-off vs. epi-on debate continues continued on page 82 The Pentacam image at the far left, 3 months after epi-off crosslinking, shows inferior steepening with K readings reaching 59.4 D at the center of the cone. The middle image taken 1.5 months prior to crosslinking shows K readings reaching 60.9 D at the center of the cone. This is evidence of cone flattening of 1.5 D at 3 months after treatment as shown in the right image. Source: Uri Elbaz, MD

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