Branch Retinal Artery Occlusion Workup
- Author: Niraj R Nathan, MD; Chief Editor: Hampton Roy, Sr, MD more...
Laboratory tests to consider in patients with suspected branch retinal artery obstruction (BRAO) include the following:
In patients older than 50 years, consider ordering an immediate erythrocyte sedimentation rate (ESR) to help rule out giant cell arteritis.
In patients younger than 50 years or in patients with the appropriate risk factors, consider the following tests to evaluate for coagulopathies: antitreponemal antibody, antiphospholipid antibody, antinuclear antibody, rheumatoid factor, serum protein electrophoresis, hemoglobin electrophoresis, prothrombin time/activated partial thromboplastin time (PT/aPTT), fibrinogen, protein C and S, antithrombin III, and factor V Leiden.
A CBC count is obtained to evaluate for anemia, polycythemia, and platelet disorders.
Fasting blood sugar, glycosylated hemoglobin, cholesterol, triglycerides, and lipid panel are obtained to evaluate for atherosclerotic disease.
Blood cultures are obtained to evaluate for bacterial endocarditis and septic emboli.
Two-dimensional or transesophageal echocardiography
Elderly patients and patients with high-risk characteristics for cardioembolic disease warrant medical workup involving either 2-dimensional or transesophageal echocardiography. High-risk characteristics include a history of rheumatic heart disease, mitral valve prolapse, prosthetic valve placement, history of subacute bacterial endocarditis, recent heart attack, intravenous (IV) drug abuse, any type of valvular heart disease (congenital or acquired), detectable heart murmurs, and ECG changes (eg, atrial fibrillation, changes indicating myocardial damage).
Carotid ultrasonography studies and magnetic resonance angiography
Considering the higher incidence of fatal stroke in the elderly population, atherosclerotic disease should be evaluated if no other etiology is obvious.
ECG/Holter monitor is used to evaluate for atrial fibrillation.
In cases of suspected Susac syndrome, MRI may be helpful to look for classic findings in the corpus callosum. Any concern for concurrent stroke symptoms would warrant the appropriate brain imaging and workup, usually guided by neurologic consultation.
Delayed filling of the affected artery and hypofluorescence in the surrounding retina will be visible immediately after onset of the occlusion. Vessels distal to the site of obstruction may show retrograde filling from surrounding perfused capillaries. Late staining of the vessel walls may be seen.
After resolution of the obstruction, flow may return to normal. However, narrowing or sclerosis of the affected artery can occur. Artery-to-artery collaterals may form in the retina and are highly suggestive of an old branch retinal artery obstruction.
Optical coherence tomography
Optical coherence tomography (OCT) has been used to demonstrate structural damage of the retinal layers after retinal artery occlusion.
One study showed diffuse thickening of the neurosensory retina where the artery occlusion occurred. Increased reflectivity was noted in the inner retinal layers with decreased reflectivity of the photoreceptors and retinal pigment epithelium, which supported the pathophysiology of increasing intracellular fluid of the inner retinal layer.
Another study used OCT to demonstrate the long-term structural result after arterial occlusion. One year after diagnosis of branch retinal artery obstruction, the authors found segmental inner retinal layer and peripapillary retinal nerve fiber layer thickness to be reduced. They correlated visual field deficits with OCT thickness and found that a worse functional outcome was associated with a more extensive thinning of the macula and retinal nerve fiber layer.
Another study suggested that spectral domain OCT may be a useful adjunct in the acute phase in characterizing retinal artery emboli, including perfusion characteristics (eg, extent of luminal occlusion) and emboli characteristics and embolus structure (eg, more crystalline in appearance or softer and more conforming to the shape of the vessel lumen).
Serial Humphrey visual field testing reveals any field deficits and can be used to monitor the stability or improvement of these deficits.
An electroretinogram (ERG) is of limited usefulness. Findings may be normal. In the case of a large branch retinal artery obstruction, it may show loss of oscillatory potential and transient depression of the B wave.
Because the prognosis for branch retinal artery occlusion (BRAO) is very good, no interventions usually are taken. In the event of involvement of the perifoveolar capillaries, treatment as for central retinal artery occlusion (CRAO) may be attempted (see Central Retinal Artery Occlusion).
Intra-arterial thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) via a guiding catheter inserted into the femoral artery, placed into the internal carotid artery, and advanced into the ophthalmic artery has been used for CRAO with varying success. This has also been applied to some patients with BRAO with limited benefit compared to conventional forms of therapy or observation.
Another procedure that has been attempted for both BRAO and CRAO is transluminal Nd:YAG laser embolysis or TYE. This method relies on the Nd:YAG laser to shatter the embolus, clear the arteriole lumen, and improve perfusion without harming the vessel wall. Potential risks include retina tears, vitreous and retinal hemorrhages, choroidal neovascularization, and epiretinal membrane formation. One study found visual improvement to occur immediately after the embolysis.
Branch retinal artery occlusion causes ischemia to the inner layers of the retina, which causes inner and intracellular edema and a coagulative necrosis.
Eventually, loss of the inner retinal layers occurs, including the nerve fiber layer to the inner nuclear layer.
Because the glial cells have also been destroyed, usually no gliosis is noted.
Histologic evidence of emboli or other etiology may be present.
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