Eyeworld

EW RESIDENTS 46 December 2011 by Ryan St. Clair, M.D., Michael Klufas, M.D., Kristine Yin, M.D., Charles Kim, M.D., and Christopher E. Starr, M.D., F.A.C.S., program director Weill Cornell Medical College residents' review of "Corneal collagen crosslinking I n the recently published article "Corneal collagen crosslinking in progressive keratoconus: Mul- ticenter results from the French National Reference Center for Kera- toconus," Asri et al. evaluated the outcomes of corneal collagen crosslinking (CXL) on patients with progressive keratoconus. The au- thors conducted a large retrospec- tive, uncontrolled, two-center study, which measured corrected distance visual acuity (CDVA), corneal pachymetry, endothelial cell count, Ocular Response Analyzer (ORA, Reichert Inc., Depew, N.Y.) parame- ters, keratometry values, and surgi- cal complications in progressive keratoconus patients 1, 3, 6, and 12 months after CXL. The CDVA stabi- lized in 48%, improved in 32.7%, and decreased in 18% of eyes at 6 months. At 12 months, CDVA stabi- lized in 47.6%, improved in 40%, and decreased in 12% of eyes. Maxi- mum keratometry (K) readings stabi- lized in 49%, decreased in 35.5%, and increased in 15.3% of eyes at 6 months. At 12 months, maximum K readings stabilized in 68.8% and de- creased in 21.3% of patients. Com- plications resulting in loss of vision occurred in 3.5% of patients. En- dothelial cell count and ORA hys- teresis were only measured in a small subset of patients, and no sig- nificant changes in these parameters were noted. We applaud Asri et al. for the multiple merits of the study. Al- though other studies have at- tempted to investigate the efficacy of CXL in keratoconus, most have been limited by small sample size; Asri et al., however, included a rela- tively large sample of 142 eyes of 142 patients. Despite the compila- tion of data from two distinct na- tional centers, the operative CXL protocol and much of the data analysis were performed in a reliable and consistent manner, allowing for reasonable generalization between sites. The evaluation parameters used in this study are consistent with those used in previous studies, allowing for some comparison of the results with those of their predeces- sors. This study affirms many of the conclusions of other large clinical trials on the efficacy of CXL in pro- gressive keratoconus, adding to the rapidly growing literature on this novel treatment. In addition, Asri et al. expand upon the current litera- ture by assessing its effect on corneal biomechanics in a limited number of study eyes and by reporting a case of "ocular burn," a complication not seen in other series. The authors also include a valuable analysis of failure indicators, noting that maximum K value greater than 58.0 D, age older than 35 years, and female gender significantly increase the rate of CXL failure. Like many non-randomized, non-controlled studies, this one is not without its limitations. As ac- knowledged by the authors, the study is a retrospective analysis, and unlike some previous studies (Wittig-Silva et al., 2008; Hersh et al., 2009), it does not include a con- trol in the form of untreated fellow eyes. A strong effort was made to standardize the treatment protocol and outcome measurements; how- ever, elevation topography and pachymetry measurements were taken using Orbscan II (Bausch & Lomb, Rochester, N.Y.) at the Bor- deaux site and Pentacam (Oculus, Lynnwood, Wash.) at the Toulouse site, potentially confounding the re- sults. The follow-up time of 1 year was significantly shorter than that of many previous studies, which fol- lowed keratoconus patients post- CXL for up to 5 years. Another potential confounding factor in the Corneal collagen crosslinking in progressive keratoconus: Multicenter results from the French National Reference Center for Keratoconus J Cataract Refract Surg (December) 2011; 37:2137-2143 Dalal Asri, M.D., David Touboul, M.D., Pierre Fournié, M.D., Florence Malet, M.D., Caroline Garra, Anne Gallois, François Malecaze, M.D., Joseph Colin, M.D. Purpose: To report refractive, topographic, and biomechanical outcomes, efficiency, and safety of corneal collagen crosslinking (CXL) 1, 3, 6, and 12 months after treatment Setting: National Reference Centre for Keratoconus, Bordeaux and Toulouse, France Design: Case series Methods: This retrospective, uncontrolled, double-center study comprised eyes with progressive keratoconus. Uncorrected distance visual acuity, cor- rected distance visual acuity (CDVA), corneal pachymetry, endothelial cell count, and corneal hysteresis and corneal resistance factor were evaluated at baseline and at 1, 3, 6, and 12 months. Results: One hundred forty-two eyes were enrolled in the study. At 6 months, the CDVA had stabilized in 53 eyes (48.1%), improved in 36 eyes (32.7%), and decreased in 18 eyes (16.3%). At 12 months, the CDVA had stabilized in 31 eyes (47.6%), improved in 26 eyes (40.0%), and decreased in 8 eyes (12%). At 6 months, keratoconus progression had stopped in 51 eyes (49.03%), and the maximum keratometry (K) value had decreased by more than 1.0 diopter (D) in 37 eyes (35.5%); it continued to progress in 16 eyes (15.3%). At 12 months, keratoconus progression had stopped in 42 eyes (68.8%), and the maximum K value had decreased by more than 2.0 D in 13 eyes (21.3%). The complication rate with loss of vision was 3.5%. Conclusions: Ultraviolet-A light associated with riboflavin CXL is an effi- cient procedure to stabilize and improve progressive keratoconus. The re- sults reinforce previous studies highlighting the efficacy and safety of the procedure. A large prospective randomized clinical trial is needed. thereby increasing the perceived height and reducing proximal ac- commodation. Adjust the eyepieces to your re- fractive error if you are not em- metropic and do not want to wear glasses. Zero the oculars if you wear glasses or contacts or have no refrac- tive error. Be careful doing this the first time as a resulting different focal point for each eye may encour- age excessive accommodation. When setting your interpupil- lary distance, begin with the oculars set well beyond your known pupil- lary distance and reducing the sepa- ration until fusion first occurs. This will minimize convergence and its accompanied accommodation. After hitting the button to cen- ter the scope under maximal zoom, grossly focus the scope from above down until the iris plane just comes into focus, then zoom out. During the case, using the least amount of magnification or zoom needed for the task you are perform- ing will give you the most natural depth of focus and thereby mini- mize the need to use the focus pedal. Periodically during longer cases look across the room when changing instruments to allow your accommodation time to relax, then fine focus from above down. If all else fails, operate with a presbyopic attending who will let you know he cannot see unless you focus back up with the foot pedal. EW Editors' note: Drs. Bailey, Kolin, and Yung have no financial interests related to this article. Contact information Bailey: rsb419@aol.com Kolin: etddk@aol.com Yung: ryung@iupui.edu Instrument continued from page 45 EyeWorld journal club From the December issue of the Journal of Cataract and Refractive Surgery This month, I asked the Cornell residents under their program director, Christopher Starr, to review this French study on collagen crosslinking for keratoconus. — David F. Chang, M.D., chief medical editor

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