They consist of partial or total obstruction of the veins of the retina.

They can be of two types:

Central venous occlusion (the central vein of the retina becomes obstructed)
Venous branch occlusion. It consists of an obstruction caused by a thrombus that occurs in the areas where the arteries and veins cross

How are they diagnosed?

To diagnose venous occlusions of the retina, a complete ophthalmological examination is required, which includes the following tests in consultation:

Fundus examination
Fluorescein angiography (FFA)
Retinography
OCT (Optical Coherence Tomography)