Retinal vein occlusion

Retinal vein occlusion. It is a common vascular disorder of the retina and a leading cause of vision loss. The condition occurs when one of the veins draining blood from the retina becomes blocked, leading to hemorrhage, edema, and ischemia. Management involves addressing the underlying systemic risk factors and treating sight-threatening complications like macular edema and neovascularization.

Signs and symptoms

Symptoms typically present as sudden, painless monocular vision loss or blurring, which can be severe in central retinal vein occlusion or more sectoral in branch retinal vein occlusion. Patients may report metamorphopsia or the appearance of floaters. On funduscopy, findings include widespread retinal hemorrhages, dilated and tortuous veins, and optic disc swelling, often described as a "blood and thunder" appearance in the ischemic form. Complications such as macular edema significantly reduce central vision, while neovascular glaucoma can cause painful elevation of intraocular pressure.

Causes and risk factors

The primary cause is a thrombus formation at sites of shared adventitial sheaths with a retinal artery, often at the lamina cribrosa or an arteriovenous crossing. Major systemic risk factors mirror those for cardiovascular disease and include hypertension, diabetes mellitus, dyslipidemia, and atherosclerosis. Other significant associations are with primary open-angle glaucoma, hypercoagulable states such as antiphospholipid syndrome, and inflammatory conditions like sarcoidosis. Age is a strong determinant, with incidence increasing significantly after age 50.

Pathophysiology

The occlusion, typically thrombotic, impedes venous outflow, causing a rise in intravascular pressure upstream. This leads to breakdown of the blood-retinal barrier, resulting in intraretinal hemorrhage, leakage of fluid, and retinal edema. Capillary non-perfusion and retinal ischemia trigger the release of vascular endothelial growth factor, which promotes pathological neovascularization of the retina, iris, or optic disc. In central retinal vein occlusion, the blockage is at the level of the optic nerve, while in branch retinal vein occlusion, it occurs at an arteriovenous crossing, usually in the superotemporal quadrant served by the superior temporal arcade.

Diagnosis

Diagnosis is primarily clinical through dilated fundus examination by an ophthalmologist. Key diagnostic tools include optical coherence tomography to quantify macular edema and assess retinal layers, and fluorescein angiography to evaluate retinal perfusion, pinpoint areas of capillary non-perfusion, and detect leakage or neovascularization. Ancillary testing may involve ultrasonography if media opacity precludes a view, and systemic workup often coordinated with a primary care physician or internist to identify underlying conditions like hyperhomocysteinemia.

Treatment

Treatment focuses on managing complications to preserve vision. First-line therapy for macular edema from branch retinal vein occlusion or central retinal vein occlusion is intravitreal anti-vascular endothelial growth factor agents like aflibercept or ranibizumab. Intravitreal corticosteroid implants such as dexamethasone are also used, particularly in pseudophakic eyes. Panretinal photocoagulation is indicated for treating neovascular complications. Management of systemic risk factors in collaboration with a cardiologist is crucial, and aspirin therapy may be considered for secondary cardiovascular prevention but does not improve ocular outcomes.

Prognosis

The visual prognosis varies by type and severity. Branch retinal vein occlusion generally has a better prognosis than central retinal vein occlusion, with many eyes maintaining useful vision. The major determinant of final visual acuity is the development and chronicity of macular edema. Ischemic forms with extensive capillary non-perfusion carry a poorer prognosis and a high risk of neovascular complications like vitreous hemorrhage or neovascular glaucoma, which can lead to profound vision loss. Regular monitoring by a retina specialist is essential for long-term management. Category:Ophthalmology Category:Retinal disorders