Abstract: Purpose: To investigate long-term ocular manifestations of ocular Behcet’s disease (BD), and the causes for blindness Methods: In August 2008, at Shariati hospital of Tehran (Behcet unit) all files of the ocular BD patients from 1976 to 2008 who were legally blind (Visual acuity=20/200 or less) at least in one eye at the last visit and had at least three years of follow-up were reviewed and the desired informations were extracted. In this retrospective, comparative, investigation, 187 patients (374 eyes) were included in this group (Group 1). They were compared with 81 nonblind (at the last visit) ocular BD patients (162 eyes) who were visited and consequently selected in 2008, our control group (Group 2). They were matched in term of the duration of BD, approximately 18 years. All patients had conventional treatments for ocular BD. Results: 65.2% (N=122) of the blind group were males vs. 56.8% (N=46) of the nonblind (control group), χ2=1.73, P=0.189. High number of initially impaired vision at presentation (vision of 20/200 or less) in the blind group; 230 eyes (61.5%) vs. 18 eyes (11.2%) in the control group was highly significant, χ2=115.6, P=0.000. More frequent cases of visible retinal vasculitis (by ophthalmoscopy) in the blind group; 290 eyes (77.5%) vs. 107 eyes (66.5%) in the control group, χ2=7.78, P=0.005, and higher frequency of vitritis and/or anterior uveitis 90.9% (N=340 eyes) vs. 75.3% (N=122 eyes) in the control group, χ2=23.01, P=0.000 were both considered two major blinding risk factors in ocular BD. At the last visit 77.3% (N=289) eyes in the main group were blind and the main cause of blindness was end-stage disease (retinal vascular necrosis and consequently chorioretinal atrophy and optic atrophy) in 38.5% (144 eyes), and the second major blinding cause was macular scar ± optic atrophy in 14.9% (N=56 eyes). Conclusion: Although ocular BD can have a very severe and blinding outcome, early detection and prompt and intensive treatments may control the disease and save the sight. Keywords: Ocular Behcet’s Disease, Blindness, Risk Factors