Retinal Venous Occlusion Flashcards
What is retinal venous occlusion?
An interruption of the normal venous drainage from the retinal tissue
What can become occluded in retinal venous occlusion?
- Central retinal vein
- Branch of the central retinal vein
What are the two possible (and sometimes overlapping) types of central retinal venous occlusion?
- Non-ischaemic CRVO
- Ischaemic CRVO
What is non-ischaemic CRVO?
A milder form of the disease that may resolve fully with a good visual outcome
What percentage of CRVO’s are non-ischaemic in nature?
75%
What is the risk of non-ischaemic central retinal venous occlusion?
It can progress to become ischaemic type
What can occur as a result of ischaemic central retinal venous occlusion?
Patient may be left with neovascular glaucoma and painful eye with severe visual impairment
Is central retinal venous occlusion or branched retinal venous occlusion more common and by how much?
Branched retinal venous occlusion is 3 times as common as central
How are branched retinal venous occlusions further classified?
Whether the affected vein is a major, minor or peripheral vessel
What is it called when (uncommonly) a vein that drains half the retina is affected?
Hemiretinal vein occlusion
What is the most common cause of retinal venous occlusion?
Thrombus formation
What are some less common causes of retinal venous occlusion?
- Disease of the vessel wall
- External compression of the vein
What happens to the blood as a result of retinal venous occlusion?
There is a backlog and stagnation which combines with hypoxia to result in extravasation of constituents causing further compression and a vicious circle is produced
What is stimulated if there is ischaemic damage to the retina?
Increased production of vascular endothelial growth factor (VEGF)
What does VEGF cause?
Neovascularisation
What can neovascularisation lead to?
- Haemorrhage
- Neovascular glaucoma
Why can neovascularisation lead to haemorrhage?
As the new vessels are of poor quality
What is neovascular glaucoma?
Where new blood vessels grow into the aqueous drainage system and cause blockage
What are the risk factors for retinal venous occlusion?
- Hypertension
- DM
- Hyperlipidaemia
- Smoking
- Obesity
- Raised IOP
- Inflammatory disease e.g. sarcoidosis
- Hyperviscosity states e.g. myeloma
- Thrombophilic disease
What does presentation of branch retinal venous occlusion largely depend upon?
Amount of compromise to the macular drainage
What does the extent of the effect on macular drainage influence?
The effect on visual acuity
What is the most common presentation of branch retinal venous occlusion?
- Unilateral, painless blurred vision
- Metamorphopsia
- Field defect