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Vacular occlusions

 

Retinal vein occlusion:
Retinal vein occlusion is commonly seen in most of the eye clinics. It is second only to diabetic retinopathy as a cause of visual loss due to retinal vascular disease. There are two forms of retinal vein occlusion.
-Branch retinal vein occlusion (BRVO)
-Central retinal vein occlusion (CRVO)
Branch retinal vein occlusion (BRVO):
It is occlusion of a portion of the circulation that drains the retina of blood. Retinal arteries supply blood to the retina. The blood then passes through the capillaries and finally drains into the venous system. With blockage of any vein there is back up pressure in the capillaries leading to fluid leakage and hemorrhages on the retina. The site of occlusion determines the extent of the hemorrhages. Branch retinal vein occlusion is by far the most common cause of retinal occlusive disease. Males and females are affected equally. Aging, high blood pressure, diabetes and smoking are all risk factors.

Central retinal vein occlusion (CRVO):
It is closure of the main retinal vein (located at the optic nerve) which collects total blood from the retina after it passes through the capillaries.
Central retinal vein occlusion is generally categorized in to two forms
-Non-ischemic
-Ischemic
The difference between the two is Ischemic type of CRVO is associated with areas of non perfusion due to significant obstruction of capillaries to cause areas with no blood supply. This type of CRVO is associated with complications like neovascularization (new vessel formation). This neovascularization leads to neo vascular glaucoma and vitreous hemorrhage. These complications are also seen in patients with BRVO.


Diagnosis:
Dilated Fundus examination: Obstructed blood vessel is dilated. Hemorrhages and edema are seen in the area of retinal vein drainage. When the blocked vein drains the macular area macular edema is seen causing gross visual loss.
Fundus fluoresceine angiography: Various vascular changes including venous dilatation, suspected area of obstruction, areas of non perfusion and areas of dye leakage from the capillaries or from new vessels are seen.
Optical coherence tomography: This test is done to detect macular edema and for following response to treatment
Treatment:
If FFA indicates that the visual loss is due to macular ischemia (closure of blood vessels that supply nutrients to the retina) it is unlikely that the vision will improve significantly over time regardless of any treatment.
Laser treatment: Patients with BRVO and CRVO should be followed frequently in order to detect any neovascularization. If FFA indicates areas of neovascularization laser surgery should be done to prevent complications like neovascular glaucoma, vitreous hemorrhage and retinal detachment.
Intravitreal Injections: Recently intraocular injection of anti VEGF drugs has shown promising results in the control of neovascularization and macular edema, also promising results have been noted in controlling macular edema following use of long acting steroid injections.

OCT pre injection showing macular edema

OCT 1month post steroid injection showing a decrease in macular edema
      
Dexamethasone intravitreal implant(OZURDEX): 0.7 mg is a biodegradable implant injected into the eye (vitreous) to treat adults with macular edema following branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO) and to treat adults with noninfectious uveitis affecting the posterior segment of the eye.

 















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