Eyeworld

67 EW INTERNATIONAL November 2018 In addition to stabilizing the cornea in keratoconus, CXL has been noted to have a mild refractive effect. One study saw a reduction in K values and topographic regu- larization from the application of CXL, alone, beginning at 3 months to 4 years after surgery. 6 Still other evidence from the literature reported improved vision and more flattening of the cornea from the combined approach. However, a comparison of ICRS alone and combined with CXL demonstrated no significant differ- ences in 121 keratoconus patients (166 eyes) for UDVA, CDVA, spheri- cal error, cylindrical error, and mean keratometry. 7 "The stability of ICRS ultimately depends on the progres- sive nature of the disease at the moment of surgery and can provide stability in patients with no clinical signs of progression. In patients with progressive disease, CXL is added," Dr. Barraquer explained. EW References 1. Raiskup-Wolf F, et al. Collagen crosslinking with riboflavin and ultraviolet-A light in kera- toconus: long-term results. J Cataract Refract Surg. 2008;34:796–801. 2. Koller T, et al. Flattening of the cornea after recovery. Although there is evidence that performing CXL after ICRS may have a small advantage, the order in which they are done seems to have little relevance, according to other studies in the literature. In another trial, investigators found that CXL that is done before ICRS may reduce the efficacy of the femtosecond laser. We in our clinic, however, support a combination of these two pro- cedures in those cases where ICRS alone are not expected to halt the progression—mostly young patients under 20 years with aggressive ker- atoconus—or otherwise progression is observed despite ICRS, adding CXL 3–6 months following the ICRS implantation," Dr. Barraquer said. CXL stops or slows the progres- sion of the ectatic process without significantly changing its shape, while ICRS implantation significant- ly flattens and regularizes the cornea without affecting the biomechan- ical properties of the cornea as the underlying cause of ectasia. A study that investigated the combination of the two procedures asked the question whether a cornea pretreat- ed with CXL would react to ICRS implantation in the expected way or would the effect be lessened by its application over a stiffer cornea. Alternatively, would CXL have the same effect on a cornea with an ICRS in place? When CXL was applied on an intact cornea, investi- gators saw an increase in uncorrect- ed distance visual acuity (UDVA) of about 1 line and corrected distance visual acuity (CDVA) of 0.5 line. There were decreases in spherical equivalent (SE) (1.39 D), manifest cylinder (0.44 D), and the mean K value (0.88 D). When CXL was performed with ICRS in place, there was an increase in UDVA and CDVA and a decrease in manifest cylinder similar to the other group, however there was a smaller decrease in SE and a larger decrease in the mean K value, although neither was statisti- cally significant. 4 Dr. Barraquer explained that a number of studies supported the advantages of combining the two surgeries, however, there was no real consensus on how to combine them. A review of the literature upheld this notion by reporting that the effects of ICRS were enhanced and stabi- lized by CXL in several studies, but the ideal combined technique was not known. 5 collagen crosslinking for keratoconus. J Cata- ract Refract Surg. 2011;37:1488–92. 3. Han Y, et al. Thinner corneas appear to have more striking effects of corneal collagen crosslinking in patients with progressive kera- toconus. J Ophthalmol. 2017:6490915. 4. Coskunseven E, et al. Effect of treatment sequence in combined intrastromal corne- al rings and corneal collagen crosslinking for keratoconus. J Cataract Refract Surg. 2009;35:2084–91. 5. Avni-Zauberman N, Rootman DS. Cross-linking and intracorneal ring segments —review of the literature. Eye Contact Lens. 2014;40:365–70. 6. Wollensak G, et al. Riboflavin/ultravio- let-a-induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol. 2003;135:620–7. 7.Cakir H, et al. Comparison of intrastromal corneal ring segment implantation only and in combination with collagen crosslinking for keratoconus. Eur J Ophthlmol. 2013;23:629– 34. Editors' note: Dr. Barraquer has no financial interests related to his comments. Contact information Barraquer: rib@barraquer.com Three months later a standard CXL protocol was applied to "fixate" the result. However, this resulted in a marked hypocorrection (+3.5 –9 x 80 degrees). Reimplanting a thinner (90 degrees x 150 µm) upper ICRS finally attained UCVA = 20/25 plano, which has been stable for more than 2 years. Source (all): Rafael Barraquer, MD

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