9

QUESTION

WHAT DO I DO WHEN I SEE A BRANCH RETINAL VEIN OCCLUSION?

Andrew M. Hendrick, MD
Michael S. Ip, MD

The diagnosis of branch retinal vein occlusion (BRVO) is made clinically. Most individuals are in their seventh decade of life and nearly two-thirds are hypertensive.¹ Other risk factors include a history of cardiovascular disease, smoking, and increased body mass. Extensive work-up following BRVO is typically not necessary in older individuals as the common risk factors are easily elicited; however, in persons under age 50 with no risk factors, a work-up may be warranted and the primary care physician consulted.

It is hypothesized that thickening of overlying branch retinal arteries within a shared adventitia results in mechanical compression of the underlying compliant venule. This occlusion of the venous circulation impairs return of blood with a spectrum of clinical findings depending on the location of the occlusion, area affected, and extent of blockage.

BRVO occurs most commonly in the superotemporal quadrant, at the junction where a branch retinal artery crosses over an underlying branch retinal vein. Sequelae of the occlusion are visible (Figure 9-1) as variable amounts of intraretinal hemorrhage, cotton-wool spots, cystoid macular edema (CME), and a tortuous dilated branch retinal vein in the affected segmental distribution distal to the site of the occluded vein. The segmental distribution is diagnostically important to distinguish BRVO from other potentially similar conditions that typically have more widespread involvement such as retinopathy from diabetes, hypertension, or radiation.

Over time, features of BRVO evolve. The intraretinal hemorrhage and any cotton-wool spots typically disappear over several weeks, although they may persist for years in some eyes. In a chronic, nonperfused BRVO, sclerosis and sheathing of the affected retinal veins may be observed. The development of venous-venous collateralization is an important feature of chronicity and provides alternative routes of venous drainage.

Fluorescein angiography (FA) is not mandatory to make the diagnosis of BRVO but can be useful to confirm the diagnosis and characterize the sequelae (Figure 9-2). FA often reveals a delay in venous filling within the area drained by the occluded vein, narrowed affected venous tributaries, and occasionally early hyperfluorescence just proximal to the site of occlusion. Retinal ischemia and posterior segment neovascularization are important sequelae of BRVO. FA is useful for distinguishing collateral vessels from neovascularization. Collateral vessels are flat and do not leak fluorescein in contrast to the 3-dimensionality and leakage of neovascularization. FA helps delineate the extent of capillary dropout to classify BRVO as perfused or nonperfused per the Branch Vein Occlusion Study (BVOS) criteria.² Although guidance from the BVOS is helpful in rendering prognosis, in clinical practice it is more useful to regard BRVO on a continuum of severity spectrum.

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