Retinal Vein Occlusion
- Author: Jesse Borke, MD, FACEP, FAAEM; Chief Editor: Robert E O'Connor, MD, MPH more...
Retinal vein occlusion (RVO) is a common vascular disorder of the retina and one of the most common causes of vision loss worldwide. Specifically, it is the second most common cause of blindness from retinal vascular disease after diabetic retinopathy. RVO has been recognized as an entity since 1855, but many aspects of the pathogenesis and management of this disorder remain uncertain. In the Canadian Journal of Ophthalmology in 2007, it was noted that "Research into CRVO is fraught with challenges, from accurate disease classification to its treatment; even the most prestigious trials have become controversial."
RVO is classified according to where the occlusion is located. Occlusion of the central retinal vein at the level of the optic nerve is referred to as central retinal vein occlusion (CRVO). Occlusion at the primary superior branch or primary inferior branch involving approximately half of the retina is referred to as hemiretinal vein occlusion (HRVO). Obstruction at any more distal branch of the retinal vein is referred to as branch retinal vein occlusion (BRVO). The location of the occlusion influences the pathogenesis, clinical presentation, and management of RVO.
RVO is further subdivided into nonischemic and ischemic types, according to the amount of retinal capillary ischemia seen by the ophthalmologist on fluorescein angiography. Such a distinction is relevant to the clinician, since two thirds of patients with the ischemic type develop the dreaded complications of macular edema, macular ischemia, and neovascularization that lead to blindness. However, the two subtypes cannot always be reliably distinguished based on physical examination alone and have little bearing on the initial management in the emergency department (ED). For these reasons, the emergency physician should focus on diagnosis and recognition of the clinical scenario, so that prompt management can commence and urgent ophthalmologic evaluation obtained.
RVO is essentially a blockage of a portion of the venous circulation that drains the retina. With blockage, pressure builds up in the capillaries, leading to hemorrhage and leakage of fluid and blood. This can lead to macular edema with leakage near the macula. Macular ischemia occurs when these capillaries, which supply oxygen to the retina, manifest leakage and nonperfusion. Neovascularization, new abnormal blood vessel growth, then occurs, which can result in neovascular glaucoma, vitreous hemorrhage, and, in late or severe cases, retinal detachment. Visual morbidity and blindness in RVO result from macular edema, retinal hemorrhage, macular ischemia, and neovascular glaucoma.
Intraluminal thrombus formation in RVO is associated with the venous stasis, endothelial injury, and hypercoagulability of the Virchow triad. In CRVO, the vein is typically occluded by thrombus formation consisting of fibrin and platelets at or posterior to the level of the lamina cribrosa. The inciting factor in BRVO is often compression of the adjacent vein by atherosclerotic retinal arteries at the site of AV crossing, leading to turbulent flow and venous stasis.[35, 32, 33, 34]
In both ischemic and nonischemic CRVO, blockage of the retinal vein occurs, but the nonischemic type is able to maintain better relative blood flow to the retina through collaterals. The nonischemic type of CRVO is the milder clinical presentation and accounts for 75%-80% of cases. Neovascularization is rare. Unfortunately, conversion to the ischemic type is common. The ischemic type is associated with marked decreased vision, as ischemic CRVO predisposes to anterior neovascularization called rubeosis irides, which leads to high-pressure neovascular glaucoma. Neovascularization in the posterior eye can lead to vitreous hemorrhage and retinal detachment.
Central retinal vein occlusion
Most patients with CRVO are older than 65 years. Most cases are unilateral, with approximately 6%-14% of cases bilateral. A study in Taiwan in 2008 noted a seasonal variation of CRVO, with a peak incidence occurring during the month of January.
Branch retinal vein occlusion
BRVO is 3 times more common than CRVO. Men and women are affected equally, with the bulk of presentations between age 60 and 70 years.
A large population-based study in Israel reported a 4-year incidence of RVO of 2.14 cases per 1000 of general population older than 40 years and 5.36 cases per 1000 of general population older than 64 years.
In Australia, the prevalence of RVO ranges from 0.7% in patients aged 49-60 years to 4.6% in patients older than 80 years.
The primary concern is vision loss; the morbidity of this disorder depends on the location of the occlusion and the degree of ischemia.
Neovascularization can result in neovascular glaucoma, vitreous hemorrhage, and, in late or severe cases, retinal detachment. Visual morbidity and blindness in RVO result from macular edema, retinal hemorrhage, macular ischemia, and neovascular glaucoma.
Central retinal vein occlusion/hemiretinal vein occlusion
The Central Venous Occlusion Study (CVOS) has helped to define visual loss morbidity in CRVO. Visual recovery in the study was found to vary, with the presenting visual acuity the best predictor of final visual acuity. Sixty-five percent of eyes with an initial acuity of 20/40 or higher had the same or better visual acuity on final evaluation. In contrast to this, only 20% of patients who presented with an initial acuity of less than 20/200 had any significant improvement in final visual acuity. HRVO generally has an outcome similar to that of CRVO.
Patients with ischemic CRVO are much more likely to have poor visual acuity, both at initial presentation and final visual acuity, compared to those with the nonischemic type.
Branch retinal vein occlusion
Patients with nonmacular BRVO may be asymptomatic, and normal visual acuity is the rule. Patients with macular involvement or edema from BRVO may have mild to (rarely) severely decreased visual acuity that may spontaneously improve within the first 3 months or so after the episode.
A large 2010 study reported the prevalence of BRVO to be 2.8 per 1000 in whites, 3.5 in blacks, 5.0 in Asians, and 6.0 in Hispanics and the prevalence of CRVO to be 0.88 per 1000 in whites, 0.37 in blacks, 0.74 in Asians, and 1.0 in Hispanics.
A population cohort study showed no significant difference between men and women in terms of incidence.
The prevalence of all types of RVO increases with age. Most CRVOs are seen in patients older than 65 years. Most BRVOs are seen in patients greater than 50 years old, with the highest rate of occurrence during the seventh and eighth decades of live. This age stratification is likely due to the association of age with atherosclerosis. When RVO is seen in younger patients, they are more likely to have an underlying coagulopathy, and patients younger than 45-50 years who lack identifiable cardiovascular risk factors should be screened for coagulopathy.
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