Thelansis

  Retinal vein occlusions (RVO) constitute a heterogeneous group of disorders characterized by impaired venous return from the retinal circulation. Classification of RVO can be subdivided into branch retinal vein occlusion (BRVO), hemiretinal vein occlusion (HRVO), and central retinal vein occlusion (CRVO), depending on the obstruction site. An occlusion within or posterior to the optic nerve head is termed CRVO, an occlusion at the major bifurcation is classified as HRVO, and any obstruction within a tributary is identified as BRVO. HRVO is often considered a distinct condition, exhibiting characteristics intermediate between BRVO and CRVO. Typical atherosclerosis risk factors are commonly associated with all types of RVO, though vein occlusions can also arise secondary to other processes such as inflammation, vasospasm, or compression. Major risk factors for BRVO include systemic arterial hypertension, arteriosclerosis, and diabetes, with additional associations reported, inclu...