Abstract
Retinal vein occlusion (RVO) is a heterogenous disorder in which the formation of a thrombus results in the retinal venous system narrowing and obstructing venous return from the retinal circulation. The pathogenesis of RVO remains uncertain, but it is believed to be multifactorial and to depend on both local and systemic factors, which can be divided into vascular, platelet, and hypercoagulable factors. The vascular factors include dyslipidaemia, high blood pressure, and diabetes mellitus. Regarding the platelet factors, platelet function, mean platelet volume (MPV), platelet distribution width (PDW), and platelet large cell ratio (PLCR) play key roles in the diagnosis of retinal vein occlusion and should be monitored. Nevertheless, the role of a hypercoagulable state in retinal vein occlusion remains unclear and requires further studies. Therefore, the following article will present the risk factors of RVO associated with coagulation disorders, as well as the acquired and genetic risk factors of thrombophilia. According to Virchow’s triad, all factors mentioned above lead to thrombus formation, which causes pathophysiological changes inside venous vessels in the fundus of the eye, which in turn results in the vessel occlusion. Therefore, a diagnosis of retinal vein occlusion should be based on both eye examination and general examination, including laboratory tests.
Highlights
Retinal vein occlusion (RVO) is a heterogenous disease, in which thrombus is formed the retinal venous system, resulting in the obstruction of venous return from the retinal circulation. The classification of this disorder depends on the site of occlusion: branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO) [1]
This is in turn degraded by activated protein C (APC)
It should be mentioned that recent reports suggest that, beside elevated values of mean platelet volume (MPV) which are observed in RVO patients, some other platelet parameters calculated from complete blood count, such as platelet distribution width (PDW) or platelet large cell ratio (PLCR)
Summary
Retinal vein occlusion (RVO) is a heterogenous disease, in which thrombus is formed the retinal venous system, resulting in the obstruction of venous return from the retinal circulation. The atherosclerotically altered retinal artery exerts pressure on the retinal vein, especially in places when they share a common adventitial sheath This pressure results in a haemodynamic disturbance in blood flow and, in consequence, to damage to the endothelium. Arterial and venous thrombosis have been classified as separate phenomena for many years, they share both many similarities in their pathophysiology, as well as their risk factors Both arterial and venous thrombosis are characterised by a hypercoagulable state, as well as inflammation, the presence of prothrombotic microparticles and excessive platelet activation [10]. In all patient age groups (≤45 years, 45–60 years, >60 years), the absence of common vascular risk factors, such as high blood pressure, dyslipidaemia or diabetes mellitus, is regarded as the indication of the presence of severe coagulation disorders [13,14]. Acquired thrombophilia involves elevated antiphospholipid antibodies in antiphospholipid syndrome and hyperhomocysteinemia [15]
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