Central retinal vein occlusion
 

There are retinal haemorrhages (dot and blot haemorrhages and flame haemorrhages) in all quadrants.  The veins are tortuous and engorged. There may be multiple cotton-wool spots. The optic disc may  be swollen in the acute stage. In chronic cases, the signs are less florid and do not omit to look for disc  collaterals, macular oedema and peripheral neovascularization. (Note: in chronic cases, the signs may be  similar to diabetic retinopathy.) Also look for: other signs of ischaemia (relative afferent pupillary defect if both pupils were not dilated)  and rubeosis iridis possible causes (for example increased cup disc ratio in glaucoma, diabetic retinopathy  and hypertensive changes in the contralateral eye)

Questions:

1. What are the risk factors for central retinal vein occlusion?

Answer
Hypertension
Diabetes mellitus
Glaucoma
Hyperviscosity syndrome

2. What are the risk factors for neovascularization in central retinal vein occlusion?

Answer
Ischaemia is the main risk factor. The signs are marked loss of central acuity, relative afferent pupillary defect, large numbers of cotton-wool spots, marked loss of visual field and widespread capillary non-perfusion as demonstrated by fluorescein angiography (this is defined as 10 disc diameter of non-perfusion which is equivalent to 50% of the retina). The dark-adapted ERG b:a wave amplitude ratio can also separate the ischaemic and non-ischaemic types of central retinal vein occlusion.

3. What is the benefit of grid laser in macular oedema secondary to central retinal vein occlusion?

Answer
The Central Retinal Vein Occlusion Study shows no evidence of visual improvement between treated and untreated macular oedema in which the visual acuity has been reduced to 20/50 or worse.

 

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