الفهرس 
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Abstract
Retinal vein occlusions (RVOs) are the second most common type of retinal vascular disorder after diabetic retinal disease. They can occur at almost any age (although typically in middle to later years - most in those aged over 65 years) and their severity ranges from asymptomatic to a painful eye with severe visual impairment.
Retinal vein occlusion is one of the most common causes of sudden painless unilateral loss of vision. Loss of vision is usually secondary to macular oedema. Occlusion may occur in the central retinal vein or branch retinal vein.
Occlusion of the retinal venous system by thrombus formation is the most common cause but other causes include disease of the vein wall and external compression of the vein .Retinal arteries and arterioles and their corresponding veins share a common adventitial sheath. It is thought that the thickening of the arteriole compresses the vein, eventually causing occlusion.
A backlog of stagnated blood combined with associated hypoxia results in extravasation of blood constituents, causing further stagnation and so on, resulting in the creation of a vicious circle of events. Ischaemic damage to the retina stimulates increased production of vascular endothelial growth factor (VEGF) which, in turn, may lead to neovascularisation a process that can result in haemorhage (as the new vessels are of poor quality) or neovascular glaucoma (the new vessels grow into the aqueous drainage system, so clogging it up). Factors contributing to this pathophysiology include:
• Advancing age
• Systemic conditions such as hypertension (found in 64% of patients with RVO).
• hyperlipidaemia, diabetes, smoking and obesity.
• Raised intraocular pressure.
• Inflammatory diseases such as sarcoidosis, Behçet’s syndrome.
• Hyperviscosity states such as myeloma .
• Thrombophilic disorders.
CRVO has two broad categories, which may overlap:
• The milder form of the disease is non-ischaemic CRVO (accounting for ~75% of CRVOs). This may resolve fully with good visual outcome or progress to the ischaemic type.
• The severe form of the disease is ischaemic CRVO. Patients may be left with neovascular glaucoma and a painful eye with severe visual impairment
The patient frequently presents with sudden unilateral painless loss of vision or blurred vision, often starting on waking.
• Non-ischaemic - mild or absent afferent pupillary defect. There are widespread dot-blot and flame haemorrhages throughout the fundus and some disc oedema.
• Ischaemic - severe visual impairment with a marked afferent pupillary defect. The fundus looks similar to the non-ischaemic picture but disc oedema is more severe. Haemorrhages scattered throughout the fundus in typical blood-storm pattern with cotton wool spots (sparse scattered
haemorrhages with less complete blockage). There may occasionally be an associated retinal detachment.
• Lines of treatment include;
• Aspirin.
• Anti-inflammatory agents.
• Isovolemic hemodilution.
• Plasmapheresis.
• Systemic anticoagulation with warfarin, heparin, and alteplase.
• Fibrinolytic agents.
• Systemic corticosteroids.
• Local anticoagulation with intravitreal injection of alteplase
• Intravitreal injection of ranibizumab.
• Intravitreal injection of aflibercept
• Intravitreal injection of triamcinolo.
• Intravitreal injection of bevacizumab .
• Dexamethasone intravitreal implant.
In our study we aimed to compare the effect of Intravitreal injection of ranibizumab versus the effect of grid laser photocoagulation on the macular oedema due to CRVO. thirty patients underwent full medical history and complete ocular examination during the first visit including; visual acuity, intraocular pressure, slit lamp and fundus examination.
After receiving three Intravitreal injection of ranibizumab in group A, grid laser photocoagulation in group B Patients were asked about symptoms of diminution of vision.
Objective clinical measures included ;OCT and snellen’s chart , After 6 months of follow up we noticed much improvement in patient of group A symptoms and signs than those in groupB. Ranibizumab proved to be more effective in treatment of macular oedema due to CRVO than grid laser photocoagulation.