Criteria
RVO is usually classified by the location of the occlusion.[4] Examination and investigation findings vary by location of occlusion as follows:
Central retinal vein occlusion (CRVO):
Four quadrants of retinal haemorrhages, vascular tortuosity and dilation, and retinal thickening
Optic nerve head oedema
Delayed central retinal venous filling on fluorescein angiogram.
Branch retinal vein occlusion (BRVO):
One quadrant of retinal haemorrhage, vascular tortuosity and dilation, and retinal thickening
Delayed branch retinal venous filling on fluorescein angiogram.
Hemiretinal vein occlusion (HRVO):
Retinal haemorrhages, vascular tortuosity and dilation, and retinal thickening limited to superior or inferior retinal hemisphere
Optic nerve head oedema may be present
Delayed filling of superonasal and superotemporal or inferonasal and inferotemporal retinal veins on fluorescein angiogram.
Ischaemic/non-perfused versus non-ischaemic/perfused RVO
Ischaemic CRVO is associated with: the presence of ≥10 disk areas of non-perfusion on 7-field fluorescein angiography and usually ≥1 of the following:[26]
Poor visual acuity (<6/60)
Relative afferent pupillary defect
Multiple dark deep intraretinal haemorrhages
Multiple cotton wool spots
Retinal vein tortuosity and dilation
Reduced b-wave amplitude, reduced b:a ratio and prolonged b-wave implicit time on electroretinogram.
In BRVO the degree of non-perfusion is important to guide treatment and prognosis:[4]
Non-perfused: presence of ≥5 disk areas of non-perfusion as assessed by fluorescein angiography.
Perfused: presence of <5 disk areas of non-perfusion.
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