This study seeks to compare dexamethasone implant with rescue intravitreal ranibizumab to monthly intravitreal ranibizumab for the treatment of macular edema secondary to branch or central retinal vein occlusion. This is based on the null hypothesis that dexamethasone implant with rescue ranibizumab has inferior best corrected visual acuity at six months compared to monthly ranibizumab alone.

Dexamethasone intravitreal implant (DEX implant; OZURDEX, Allergan, Inc., Irvine, CA) and Ranibizumab (Lucentis, Genentech, Inc., South San Francisco, CA) as needed group:

• Patients will receive a dexamethasone intravitreal implant injection at day 0. Injection procedure will be identical to those previously described.8,19,20 Topical tetracaine drops will be given, a lid speculum inserted, and then 5% povidone iodine drops will be given. After subconjunctival injection of 2% lidocaine, the 0.7mg DEX implant will be inserted through the pars plana using a customized, single use, 22-gauge applicator. Patients will be treated with topical ophthalmic antibiotics four times daily for three days after the procedure.
• During monthly visits 1,2,3, and 5, patients will receive a ranibizumab intravitreal injection if the macula SD-OCT during that visit shows mean central foveal thickness ≥ 250 μm or the best-corrected visual acuity is 20/40 or worse. The injection procedure is described in the next section.
• During monthly visit 4, patients will receive a dexamethasone intravitreal implant injection if the macula SD-OCT during that visit shows mean central foveal thickness ≥ 250 μm or the best-corrected visual acuity is 20/40 or worse.

Monthly Ranibizumab (Lucentis, Genentech, Inc., South San Francisco, CA) group:

• Patients will receive a ranibizumab intravitreal injection on day 0. During each other visit, patients will receive a ranibizumab intravitreal injection. The protocol will use the term "monthly" to represent a 30 day interval between treatments. The minimal interval between treatments may be 25 days.
• Injection procedures will be identical to those previously described.8,19,20 Topical tetracaine drops will be given, a lid speculum inserted, and then 5% povidone iodine drops will be given. After subconjunctival injection of 2% lidocaine, a 30-gauge needle will be inserted through the pars plana, and 0.5 mg (0.05mL) of drug injected.

Inclusion Criteria:

• Signed informed consent form
• 18 to 90 year-old men or women
• Women must be postmenopausal for at least 12 months before study enrollment, or surgically sterile. Potential child bearing women must have a negative serum pregnancy test within 14 days prior to the first treatment and practice effective contraception during and at least 120 days following the last dose of injection.
• Patient of the Wills Eye Institute Retina service, including all Mid-Atlantic Retina offices.
• Healthy enough to participate in the study.
• Willing and able to consent to participation in the study.
• Retinal vein occlusion:
• Must be diagnosed within two weeks of onset of symptoms
• Best Corrected Visual Acuity (BCVA) on initial presentation between 20/40 and 20/320
• No contraindications to intravitreal injection of dexamethasone implant or ranibizumab
• Central foveal thickness greater than 250 m on Spectral Domain-OCT

Exclusion Criteria:

• Unknown duration of symptoms prior to diagnosis.
• Patients with any history of prior intravitreal dexamethasone or anti-VEGF or grid laser.
• Patients with diabetic retinopathy.
• Patients with age-related macular degeneration.
• Patients with an optic neuropathy.
• Patients with a retinal detachment or history of retinal detachment.
• Patients with a significant epiretinal membrane.
• Patients with a history of choroidal neovascularization.
• Patients with glaucoma with visual field loss documented on a Humphrey Visual Field test or ocular hypertension requiring more than 2 medications to control IOP in the study eye.
• Patients with a clinically significant media opacity.
• Patients using or anticipating using systemic steroids.
• Patients with any uncontrolled systemic disease.
• Patients with aphakia or anterior-chamber intraocular lens.
• Patients with active neovascularization of the iris, disc, or retina.