Retinal Vein Occlusion
Retinal vein occlusion [Branch Retinal Vein Occlusion (BRVO), Central Retinal Vein Occlusion (CRVO)] are vascular occlusions of either the branch or central retinal vein resulting in potential vision changes and long term sequelae.
- Central Retinal Vein Occlusion (CRVO) occurs with a thrombus occludes the central retinal vein near the lamina cribosa (Green, 1981)
- Branch Retinal Vein Occlusion (BRVO) occurs when a thrombus occurs at the arteriovenous crossing point secondary to atherosclerosis of the retinal artery causing compression and occlusion of the retinal vein. (Frangieh, 1982)
- Open angle glaucoma
- Diabetes mellitus
- Cardiovascular disease
- Open angle glaucoma
- High body mass index (not diabetes mellitus)
- CRVO – A thrombus forms at the central retinal vein near the lamina cribosa (Green, 1981)
- BRVO – Arterial compression of the vein at the arteriovenous crossing causes turbulence which may lead to endothelial cell damage and thrombus formation (Frangieh, 1982)
Retinal vein occlusions can cause macular edema, retinal ischemia, neovascular complications such as glaucoma, vitreous hemorrhage and retinal traction.
Optimal management of associated risk factors.
Diagnosis is based upon the retinal examination findings of intraretinal hemorrhages, dilated veins, and often cotton wool spots often described as a "blood and thunder appearance" for CRVO. There may be macular edema also present.
Patients often present with acute vision loss. They may have a history of cardiovascular disease, diabetes mellitus and/or hypertension.
Clinicians should consider performing an undilated slit lamp anterior segment examination with gonioscopy to look for neovascularization of the angle prior to a dilated fundus examination with ophthalmoscopy. In addition, fluorescein angiography and optical coherence tomography (OCT) may supplement clinical decision making. Fluorescein angiography is useful for determining the degree of ischemia present. OCT is useful for monitoring macular edema.
Retinal vein occlusions demonstrate variable degrees of intraretinal hemorrhage, cotton wool spots, macular edema, subretinal fluid, collateral vessels (chronic), iris and retinal neovascularization, dilated and tortuous veins, and sclerotic vessels with atrophy when chronic.
Common: Central or peripheral monocular vision loss. Less common: Transient visual obscurations or asymptomatic
Since the differential diagnosis is limited, retinal vein occlusions are often diagnosed with history and physical examination alone.
Fluorescein angiography may be used to determine the degree of retinal ischemia and diagnose macular edema. This may be important for prognostic reasons and to predict the development of neovascular sequelae. Optical coherence tomography may be used to diagnose macular edema and gauge response to treatment.
In older patients with cardiovascular risk factors, no laboratory tests are needed. In atypical cases such as younger patients and bilateral or recurrent retinal vein occlusions, laboratory tests such as a complete blood count, fasting serum glucose, serum protein electrophoresis, homocysteine, serum viscosity, and thrombophilic screening (factor V Leiden mutation, protein C or S deficiency, antithrombin III deficiency, antiphospholipid antibodies) may be considered.
Ocular ischemic syndrome, diabetic retinopathy, human immunodeficiency virus (HIV) retinopathy, hypertensive retinopathy, retinopathy related to blood dyscrasias
No treatment is available to reverse retinal vein occlusions. However, the iris/retinal neovascularization or macular edema may be managed with anti-vascular endothelial growth factor (VEGF) or steroid injections. Macular edema in BRVO may also be managed with grid laser photocoagulation. Please refer to the EyeWiki BRVO and CRVO pages for detailed discussions of treatment options.
Medical therapy can limit complications from retinal vein occlusions. Anti-VEGF intraocular injections can induce regression of iris neovascularization (Ciftci, 2009) and decrease macular edema (Spaide, 2009; Kondo, 2009). In addition, the SCORE study demonstrated the benefit of triamcinolone acetonide for macular edema secondary to central retinal vein occlusions (vs. sham) (Ip, 2009) but did not demonstrate benefit for branch retinal vein occlusions (vs. focal laser) (Scott, 2009).
The first-line therapy for macular edema with either CRVO or BRVO is currently anti-VEGF injections . Both ranibizumab (BRAVO and CRUISE) and aflibercept (GALILEO/COPERNICUS; VIBRANT)  have been shown to be efficacious in the treatment of macular edema. Significant gains in visual acuity have been demonstrated along with improvement in macular edema with therapy. Both drugs are recommended to be used monthly for the first 6 treatments and then as needed. Bevacizumab is also used off-label to treat macular edema and neovascularization in CRVO and BRVO.
Steroid implants, such as the dexamethasone implant (OZURDEX)  has also been FDA-approved to treat macular edema in CRVO and BRVO. It is generally used as a second-line therapy or for eyes with chronic edema that is poorly responsive to anti-VEGF injections.
The SCORE2 Study compared aflibercept with bevacizumab for macular edema due to CRVO using a non-inferiority trial design. The primary endpoint was at 6 months. Bevacizumab was non-inferior to aflibercept with respect to visual acuity and OCT thickness.  After 6 months, good responders were divided into monthly and treat and extend (TAE) regimens using the original assigned drugs. No significant difference was seen between monthly and TAE for each drug. There were fewer treatments given for the TAE arms as compared to monthly.  Poor responders at 6 months were assigned a different treatment: aflibercept eyes were assigned to dexamethasone implant and bevacizumab eyes were assigned to aflibercept. The numbers of poor responders were too small in both groups to make a definitive recommendation. However, visual acuity improved in both groups after switching.
Medical follow up
Ischemic retinal vein occlusions can cause iris or retinal neovascularization in addition to macular edema and should be monitored with an undilated iris and angle examination followed by a dilated fundus examination on a periodic basis. CRVO eyes should be examined monthly for 6 months. The risk is highest for development of rubeosis within the first 90 days and decreases through 6 months. This risk may be delayed if the patient is receiving anti-VEGF injections. Therefore, patients with ischemic retinal vein occlusions who later discontinue anti-VEGF therapy need to be watched closely. In general, fluorescein angiography should be delayed until retinal hemorrhages clear to allow for good visualization of the choriocapillaris.
The Central Retinal Vein Occlusion Study supported panretinal photocoagulation for iris neovascularization after it occurs. (CVO Study Group N Report, 1995) It did not support grid photocoagulation for macular edema. (CVO Study Group M Report, 1995) The Branch Vein Occlusion Study supported the use of grid laser photocoagulation of edematous area. (BVO Study Group, 1984) In addition, The BVO Study Group recommended sectoral panretinal photocoagulation for the development of retinal neovascularization. (BVO Study Group, 1986)
Surgical follow up
Complications associated with intravitreal injections include infection, hemorrhage, retinal detachment, cataract, and both infectious and sterile uveitis; however, these complicatations remain relatively rare. Triamcinolone acetonide and dexamethasone implant can also cause a steroid-induced glaucoma.
The prognosis is highly variable depending on the location of the retinal vein occlusion, degree of ischemia, and development of sequelae. Please see EyeWiki BRVO and CRVO pages for more in depth information.
- Boyd K, Janigian RH. Central Retinal Vein Occlusion. American Academy of Ophthalmology. EyeSmart® Eye health. https://www.aao.org/eye-health/diseases/central-retinal-vein-occlusion-list. Accessed April 04, 2019.
- Boyd K, Vemulakonda GA. Branch Retinal Vein Occlusion (BRVO). American Academy of Ophthalmology. EyeSmart® Eye health. https://www.aao.org/eye-health/diseases/branch-retinal-vein-occlusion-brvo-list. Accessed April 04, 2019.
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