Description
In branch retinal vein occlusion (BRVO) there is a tendency for the occlusive thrombus to occur at arteriovenous crossings, where the stiff-walled atheromatous artery may compress the lumen of the adjacent thin-walled vein, creating blood turbulence and thrombotic build-up. BRVO shows a strong association with systemic diseases such as hypertension, diabetes and hyperlipidaemia, as well as with arterial diseases such as atherosclerosis and carotid artery disease, temporal arteritis, and hypercoagulation or vasculitis disorders. The condition is also associated with ocular conditions, including raised intraocular pressure (IOP), von HippelLindau disease, Coats disease and Eales disease.
Symptoms
The patient may notice a BRVO if it affects a large area of retina or the macula itself. There may be a prior history of brief loss of vision (amaurosis fugax), transient ischemic attack fTIA) or stroke (cerebrovascular accident).
Signs
Initial signs of BRVO are flame, dot and blot hemorrhages adjacent to a dilated and tortuous vein. The condition is usually unilateral, localized to one area of retina, and does not usually cross the horizontal midline. BRVOs may be characterized by:
- Distance of the occlusion from the optic disc, which dictates the size of
the affected area of retina - Presence of macular edema, affected by the proximity of the occlusion to the macula, which in turn affects the visual prognosis
- Presence of retinal ischemia – more likely if there are signs such retinal edema and cotton-wool spots. Retinal
ischemia is assessed via fluorescein angiography.
- Time since the occlusion – further signs may develop in the natural course of the BRVO, if adequate venous drainage does not redevelop.
The natural course of BRVO is associated with a relatively good prognosis in many cases. However, possible changes include:
- Collateral vessels may develop in the months after an occlusion to improve the blood flow away from the affected zone. Unlike neovascularization, collateral vessels are not leaky and are considered a beneficial change in the resolution of the BRVO.
- Arterial macroaneurysms result from focal damage to the vessel wall. They appear as an isolated swelling of the vessel and carry the risk of leakage (see BRVO – sequelae).
- Lipid (hard) exudates may be precipitated from the leaky vessels. They are dense, waxy and yellow in color, and usually preceded by retinal edema. Inthe macular area, the exudates may appear like a radiating star (see BRVO – sequelae).
- Other possible changes include neovascularization, vitreous hemorrhage, fibrosis, retinal detachment and, rarely, neovascular glaucoma.
Prevalence
BRVO is the second most common vascular disease affecting the retina after diabetic retinopathy. Although, overall, vascular occlusions are uncommon (1 : 1000), they are relatively common (1 : 100) in specific at-risk groups, such as people aged over 50 years.
Significance
BRVOs may be vision threatening, and also flag the risk of potentially life
Description, symptoms, signs, prevalence, significance, differential diagnosis, see also See Branch retinal vein occlusion – assessment.
Description
Urgent Initial management relates to any underlying systemic disease or possible glaucoma. Treatment may help to reduce the risk of stroke (cerebrovascular accident) or an additional subsequent ocular vascular occlusion.
Btood tests Patients need a full blood work-up to treat any underlying systemic risk factors such as hypertension, diabetes, carotid stenosis or cardiovascular disease.
Oral medication Review antihypertensive and other medications, and consider daily aspirin. Consider discontinuing oral contraceptives if being taken.
Ocular tests Risk factors for glaucoma should be evaluated, and intraocular pressure reduced if necessary. Assess for neovascularization of the disc or elsewhere on the retina. Neovascularization of the iris, anterior angle or neovascular glaucoma are rarer complications. Fluorescein angiography may be indicated to assess retinal capillary nonperfusion; the presence of an area of more than five disc diameters is a risk for development of neovascularization. Usually a fluorescein angiography is indicated 2-3 months after a BRVO, once the hemorrhages have cleared.
Laser treatment In many patients with BRVO, no laser treatment may be necessary. However, recognized indications are macular edema or neovascularization. Grid argon laser treatment for macular edema is indicated in the presence of:
- Reduced visual acuity (<20/40)
- Good macular perfusion, with intact capillaries evident on angiography
- Resolution of most of the adjacent hemorrhages (Branch Retinal Vein Occlusion Study or BRVOS).
The natural course of BRVO is associated with a relatively good prognosis in many cases. However, possible changes include:
- Collateral vessels may develop in the months after an occlusion to improve the blood flow away from the affected zone. Unlike neovascularization, collateral vessels are not leaky and are considered a beneficial change in the resolution of the BRVO.
- Arterial macroaneurysms result from focal damage to the vessel wall. They appear as an isolated swelling of the vessel and carry the risk of leakage(see BRVO – sequelae).
- Lipid (hard) exudates may be precipitated from the leaky vessels. They are dense, waxy and yellow in color, and usually preceded by retinal edema. Inthe macular area, the exudates may appear like a radiating star (see BRVO – sequelae).
- Other possible changes include neovascularization, vitreous hemorrhage, fibrosis, retinal detachment and, rarely, neovascular glaucoma.
Prevalence BRVO is the second most common vascular disease affecting the retina after diabetic retinopathy. Although, overall, vascular occlusions are uncommon (1 in 1000), they are relatively common (1 in 100) in specific at-risk groups, such as people aged over 50 years.
Significance BRVOs may be vision threatening, and also flag the risk of potentially life
Fig. 17.1
Hemorrhages, exudates and cotton-wool spots associated with a superior temporal branch vein occlusion. The macula is affected, impacting on the patient’s visual acuity.
Fig. 17.2
Long-standing superior temporal branched retinal vein occlusion. with collateral vessels just above the disc, sheathed retinal veins and aneurysms above the macula.
threatening systemic conditions such as stroke, requiring prompt investigation and treatment.
Differential diagnosis
Central retinal vein occlusion; commotio retinae; ocular ischemic syndrome (all usually unilateral); hypertensive retinopathy; diabetic retinopathy (usually bilateral).
See also
Branch retinal vein occlusion – sequelae; branch retinal artery occlusion; central retinal artery occlusion.
Management
See Branch retinal vein occlusion management.