Retinal Vein Occlusions

Patient usually present with decreased vision of the affected eye. Dilated fundus examination findings in retinal vein occlusions include tortuosity and dilation of the retinal veins, superficial retinal hemorrhages, retinal edema, often cotton-wool spots (areas of retina nerve fiber layer infarcts), and with time, the corresponding arteries may become narrowed and sheathed. 

Risk factors for retinal vein occlusions include: 

Systemic hypertension, diabetes, history of glaucoma and hardening of the arteries (arteriosclerosis). Other risk factors are oral contraceptives and any disease the cause alteration in clotting mechanism and blood viscosity. 

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Retinal vein occlusions can subdivided in two categories:

1 -Branch retinal vein occlusions

2- Central retinal vein occlusions

Branch retinal vein occlusions (BRVO):

Involve only a sector of the retina drained by the affected vein. Occlusion occurs most commonly at an arteriovenous crossing where common adventitia binds the artery and the vein together and that thickening of the arterial wall compress the vein, resulting in turbulence of flow, endothelial cell damage and thrombotic occlusion.

Central retinal vein occlusion (CRVO):

All the areas of the retina are affected. Thrombosis of the central retinal vein occurs at and posterior to the level of the lamina cribrosa. 

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Vision can be affected by:

Macular edema, macular edema with lipid exudates, macular ischemia, pigmentary macular disturbances, subretinal fibrosis and epiretinal membrane formation. Less commonly, vision is lost from vitreous hemorrhage or tractional and/or rhegmatogenous retinal detachment. Other complication is development of neovascular glaucoma. 

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Retinal vein occlusions can be diagnosed by characteristics findings during dilated fundus examination. Optical coherence tomography (OCT) is used to evaluate the presence and severity of the macular edema and fluorescein angiography (FA) gives us information about the degree of ischemia and presence of abnormal neovascularization. 

Macular edema is usually treated with intravitreal injections (anti-vascular endothelial growth factors, steroids or steroid implants). Focal laser is also an option in selected cases. Panretinal photocoagulation is recommended is the presence of iris or retina neovascularization or severe ischemia. Parsplana vitrectomy is recommended when unclearing or severe vitreous hemorrhage is present and in cases of retina detachment. Glaucoma medications, glaucoma specialist evaluation and possible glaucoma surgery needed if the patient develops neovascular glaucoma.