Research Article Differentiation between Good and Low-Responders to Intravitreal Ranibizumab for Macular Edema Secondary to Retinal Vein Occlusion Marcel N. Menke, 1,2 Andreas Ebneter, 2 Martin S. Zinkernagel, 2 and Sebastian Wolf 2 1 Department of Ophthalmology, Cantonal Hospital Aarau, Aarau, Switzerland 2 Department of Ophthalmology, Inselspital, University Hospital of Bern and University of Bern, Bern, Switzerland Correspondence should be addressed to Marcel N. Menke; marcel.menke@gmail.com Received 29 August 2016; Revised 20 October 2016; Accepted 1 November 2016 Academic Editor: Miguel Cordero-Coma Copyright © 2016 Marcel N. Menke et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Ranibizumab is approved for treatment of macular edema in eyes with retinal vein occlusion (RVO). Some eyes show low-response to treatment with regard to visual acuity gain (VA) and OCT central retinal thickness (CRT) reduction. Te goal of this study was to quantify the percentage of low-responders. Methods. Treatment of na¨ ıve eyes with macular edema secondary to RVO was included and monthly VA and CRT were analyzed. Four weeks afer the loading phase, and at the end of the study, eyes were grouped into low- and good responders based on predefned criteria. Te responder and low-responder groups were then compared at various time points. Results. Forty-three eyes were included. Regarding VA, 27.9% were low-responders afer the loading phase and 30.2% at the end of the study. For CRT, 34.9% were low-responders afer the loading phase versus 27.9% at the end of the study. 75% of patients that were VA low-responders and 73.3% of CRT low-responders afer loading phase remained low-responders at the end of the study. Conclusion. Approximately 30% of patients showed low response to ranibizumab afer the loading phase and afer 1 year of treatment. Two-thirds of patients that were low-responders afer the loading phase remained low-responders afer 1 year. 1. Background Central retinal vein occlusion (CRVO) is characterized by blockage of the major outfow vessel of the retina, resulting in retinal hemorrhages, exudates, and macular edema [1]. In branch retinal vein occlusion (BRVO), one of the primary, secondary, or tertiary branches of the central retinal vein are blocked [2]. BRVO leads to similar retinal problems and visual loss due to macular edema if the posterior pole is afected. Intravitreal injection of ranibizumab (Lucentis; Genen- tech, Inc., South San Francisco, CA), a Fab fragment that binds all isoforms of VEGF-A, has been shown to markedly reduce macular edema. Two large, multicenter, double- masked trials—the Ranibizumab for the Treatment of Mac- ular Edema following Branch Retinal Vein Occlusion Study (BRAVO) [3] and the Ranibizumab for the Treatment of Macular Edema afer Central Retinal Vein Occlusion Study (CRUISE) [4] analyzed the efcacy and safety of intravit- real ranibizumab in either types of retinal vein occlusion. Te study results showed that intraocular injections of ranibizumab were benefcial for these patients. Te HORIZON trial (ClinicalTrials.gov identifer: NCT00379795) was designed to obtain additional informa- tion about the long-term efcacy of ranibizumab treatment in two patient cohorts. Cohort 1 included patients with neo- vascular age-related macular degeneration and will not be discussed further. Cohort 2 included patients with macular edema afer retinal vein occlusion that had completed the BRAVO or CRUISE studies [5]. Recently, Bhisitkul et al. reanalyzed data from BRAVO and CRUISE to see if optical coherence tomography (OCT) data at baseline or month 3 Hindawi Publishing Corporation Journal of Ophthalmology Volume 2016, Article ID 9875741, 6 pages http://dx.doi.org/10.1155/2016/9875741