EyeWorld Asia-Pacific December 2016 Issue

EWAP SECONDARY FEATURE 29 December 2016 penetration of rose bengal is not as deep as riboflavin. 2 In a study on this, rose bengal was applied to the rabbit cornea and a green light turned on afterward. “When we looked at the amount of crosslinking and compared the two, it was equivalent,” Dr. Melki said. In his view, the most obvious advantage of the rose bengal is that it would enable practitioners to treat thinner corneas. “Once you start thinning with keratoconus, after a certain level you’re not able to use riboflavin anymore,” he said. While some hypoosmolar solutions can swell the cornea, once you get below a certain level, even that is not going to help, he pointed out. In Dr. Wilson’s view, crosslinking will become an important part of many practices and provide a new tool that will further decrease the incidence of penetrating keratoplasty. “That’s a good thing because while transplants in patients who need them are a wonderful thing—they restore vision, but they also have a high rate of rejection—it takes a long time for the patient to get useful vision in many cases, and we struggle with problems like abscesses from sutures breaking or high astigmatism,” Dr. Wilson said. “I think the more we can reduce penetrating keratoplasty, the better off we are.” EWAP References 1. Torricelli AA, et al. BACEDTA transepithelial riboflavinUVA crosslinking has greater biomechanical stiffening effect than standard epitheliumoff in rabbit corneas. Exp Eye Res . 2014;125:114–7. 2. Zhu H, et al. Corneal crosslinking with rose bengal and green light: efficacy and safety evaluation. Cornea . 2016;35:1234–41. Editors’ note: Dr. Melki and Dr. Wilson have no financial interests related to their comments. Contact information Melki : melki@bostonlaser.com Wilson : WILSONS4@ccf.org Views from Asia-Pacific Gerard SUTTON, MD Ophthalmologist gerard.sutton@visioneyeinstitute.com.au Christopher HODGE, PhD Clinical Research Coordinator christopher.hodge@visioneyeinstitute.com.au Vision Eye Institute 3/270 Victoria Avenue, Chatswood, NSW, Australia 20167 Tel. no. +612-94249999 Fax no. +612-94103000 C rosslinking is making a real impact upon rates of corneal transplantation. 1 This is a reflection of strong long-term safety and efficacy data that supports the use in cases of progressive keratoconus. 2 As this month’s article suggests, we now have available a number of options for crosslinking that demand our attention. It is critical however that we maintain a healthy scepticism about new protocols until additional robust large-scale data become available. Transepithelial techniques reportedly offer “less risk of infection, greater postoperative comfort and fewer issues with aggressive wound healing” than standard epithelial-off protocols. This is important; however, with complication rates already low in epithelial-off literature, it is the stabilizing of the cornea that remains paramount. If a patient has progressive disease, there is no value in treating them half-heartedly. Currently, only two prospective, randomized controlled studies comparing epithelial on and off techniques are available at relatively long term. 3, 4 Although both studies have suggested no significant difference in corrected visual acuity at 24 months, epithelial-off crosslinking provided greater improvement in keratometry values and was more effective stabilizing the condition and limiting regression. Of significance to the current article, Rush et al. incorporated the extensive use of benzalkonium chloride during the transepithelial dosing stage suggesting no additional clinical benefit for this revision. 4 Longer term data is still essential and we look forward to these outcomes. The potential of rose bengal and green light irradiation as an alternative to riboflavin and UVA is proposed in a number of reports. Consistent across the literature however remains the decreased penetration of rose bengal/green light compared to standard technique. 5, 6 This is reflected clinically by the reduced effectiveness in minimising keratometric change. This is clearly not optimal for our patients. Dr. Melki suggests a niche role in the treatment of thinner corneas due to the rose bengal’s relative lack of corneal penetration. This makes some sense, as does the corresponding use of transepithelial techniques; however, once again long-term comparative, controlled trials are required to tease out whether or not these options represent a more effective process. The large variability in published outcomes almost certainly reflects the lack of a consistent gold standard measure for corneal biomechanical parameters. This remains a particular consideration when discussing the effectiveness of treatments. Perhaps a more appropriate goal is to increase our general understanding of keratoconus and early diagnosis of at-risk patients. This will ultimately provide the best path forward in our goal to minimise (or eradicate) this condition. References 1. Godefrooij DA, Gans R, Imhof SM, Wisse RP. Nationwide reduction in the number of corneal transplantations for keratoconus following the implementation of cross-linking. Acta Ophthalmol . 2016 Nov;94(7):675-678. 2. Gomes JA1, Tan D, Rapuano CJ, Belin MW, Ambrósio R Jr, Guell JL, Malecaze F, Nishida K, Sangwan VS; Group of Panelists for the Global Delphi Panel of Keratoconus and Ectatic Diseases. Global consensus on keratoconus and ectatic diseases. Cornea . 2015 Apr;34(4):359-69. 3. Bikbova G, Bikbov M. Standard corneal collagen crosslinking versus transepithelial iontophoresis-assisted corneal crosslinking, 24 months follow-up: randomized control trial. Acta Ophthalmol . 2016 Nov;94(7):e600-e606. 4.RushSW,RushRB.Epithelium-offversustransepithelialcornealcollagencrosslinkingforprogressivecornealectasia:arandomised and controlled trial. Br J Ophthalmol . 2016 Jul 7. pii: bjophthalmol-2016-308914. doi: 10.1136/bjophthalmol-2016-308914. 5. Singh M, Li J, Han Z, Vantipalli S, Liu CH, Wu C, Raghunathan R, Aglyamov SR, Twa MD, Larin KV. Evaluating the Effects of Riboflavin/UV-A and Rose-Bengal/Green Light Cross-Linking of the Rabbit Cornea by Noncontact Optical Coherence Elastography. Invest Ophthalmol Vis Sci . 2016 Jul 1;57(9):OCT112-20. 6. Bekesi N, Kochevar IE, Marcos S. Corneal Biomechanical Response Following Collagen Cross-Linking With Rose Bengal-Green Light and Riboflavin-UVA. Invest Ophthalmol Vis Sci . 2016 Mar;57(3):992-1001. Editors’ note: Drs. Sutton and Hodge declared no relevant financial interests.