Hello and welcome to the zero to finals podcast. My name is Tom and in this episode I'm going to be talking to you about retinal vein occlusion. And you can find written notes on this topic at zero to finals.com slash retinal vein occlusion or in the ophthalmology section of the second edition of the

zero to finals medicine book and you can find flashcards and questions to train your knowledge

and help you remember the information for longer at members.0.0.com. So let's get straight into it. Retinal vein occlusion occurs when a blood clot

or a thrombus forms in the retinal veins, blocking the drainage of blood from the retina.

The thrombus may form in the central retinal vein or a branch retinal vein.

The branch retinal veins drain into the central retinal vein,

which runs through the optic nerve to drain into either the superior ophthalmic vein

or the cavernous sinus.

Blockage of one of the branch veins affects the area drained by that branch.

Blockage in the central vein causes problems with the whole retina.

The sites where the retinal arteries cross over the top of the veins can cause narrowing of

the vein. These sites are at higher

risk of occlusion. Blockage of a retinal vein causes venous congestion in the retina. Increased pressure

in the retinal veins results in fluid and blood leaking into the retina, causing macular odema and retinal hemorrhages,

leading to retinal damage and vision loss.

Retinal vein occlusion can be categorized as ischemic or non-ischemic.

Ischemia refers to restricted or reduced blood flow and oxygen to a particular tissue.

Retinal ischemia leads to the release of vascular endothelial growth factor or VEGF,

resulting in new blood vessel development, which is called neovascularization.

Let's talk about the risk factors.

The risk factors for retinal vein occlusion are hypertension or high blood pressure,

high cholesterol, diabetes, smoking, a high plasma viscosity, for example with conditions like myeloma,

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