Central Retinal Vein Occlusion
Increased venous back pressure and the hypoxia of venous stasis cause widespread retinal hemorrhages. The hemorrhages alongside the veins have a feather-like shape because they lie between the ganglion cell axons in the retina's most superficial layer. They are so numerous that some people call this the "tomato catsup fundus."
Compare these hemorrhages with the others that occur in the retina (see Retinal Hemorrhages).
Distended retinal veins
Notice that the retinal veins are almost twice normal in caliber. This is because of increased pressure within their walls, owing to downstream occlusion.
Retinal vein occlusion
The patient presents with painless loss of vision, often mixed with sparkles, that may be sudden or evolve over hours to days. Systemic hypertension is the most common cause; hyperviscous and hypercoagulable states must also be considered.
What to do?
Refer to an ophthalmologist urgently, although there is no immediate treatment. (Anticoagulation is not used as it is for venous occlusion elsewhere in the body).
The blood eventually resolves, but recovery of vision varies depending on how severe the ischemia has been. In cases of severe ischemia, new blood vessels may develop within months on the surface of the iris (). These new vessels eventually "zipper up" the anterior chamber angle structures, impede the exit of aqueous, and drive intraocular pressure sky high. This "neovascular glaucoma" causes severe pain and further loss of vision. Pan-retinal photocoagulation may reverse this process.