Retinal vein occlusion occurs when the veins which responsile to drain the blood from retina are blocked due to blood clots or narrowing of the vessels. This causes the accumulation of the blood in the retina. Retinal vein occlusion also causes the formation of new blood vessels which are weak and can easily leak. The center part of the retina is called the macula, hence the blood leaking into the macula causes swelling which lead to macular edema. This condition affects the vision and results in blurring of vision, double vision, a sensation of foreign body in the eye, reduced color vision, and blindness. Macular edema due to retinal vein occlusion can be diagnosed with a fundoscopic examination, visual field test, visual acuity, color blindness test and optical coherence tomography (OCT). It can be treated with laser photocoagulation, intraocular steroid injections, intravitreal vascular endothelial growth factor inhibitor injections, and vitrectomy.