 Risks of intravitreal injections are well known and include endophthalmitis and retinal detachment. This risk should be less than 1 with proper injection technique and experienced retinal surgeons. As the incidence of neovascular glaucoma with resultant loss of central and peripheral visual fields is approximately 50 in ischemic CRVO, the small risk of intravitreal injection is warranted if the drug shows efficacy. In a small number of subjects in previous animal and human trials, intraocular pressure was acutely elevated when the drug volume was placed intravitreally. An eye with a compromised circulation such as ischemic CRVO may experience less perfusion if this occurred. Previous intravitreal studies of ranibizumab have not utilized anterior chamber paracentesis to compensate for the volume of intravitreal drug to be placed. This was reasonable because an eye with a normal retinal circulation can tolerate relatively high intraocular pressure for a limited time. This protocol for this study will include anterior chamber paracentesis prior to intravitreal injection to minimize this potential risk. 