Retinal Vein Occlusion
Retinal vein occlusion (RVO) is most commonly associated with advancing age and hypertension; however, it also has less common or rare associations. A patient with RVO should be medically evaluated, and, in the absence of cardiovascular disease, a search for other causative or predisposing systemic conditions should be considered, especially among patients younger than 50 years old.
All patients with RVO should undergo a comprehensive ocular examination. Glaucoma, in both open- and narrow-angle forms, is a major risk factor for RVO. In the Eye Disease Case-Control Study (EDCC), a history of glaucoma was found to increase a patient’s risk of CRVO by a factor of 5.3, and of BRVO by a factor of 2.5. Elevated retinal venous pressure and reduced blood flow are thought to be among the few avoidable factors associated with both branch and central retinal vein occlusion. Retinal venous pressure may increase in the supine position (ie, when sleeping), and blood pressure medications can reduce perfusion pressure and blood flow; therefore, it has been suggested that patients should avoid taking their blood pressure medications at bedtime.
Intraretinal hemorrhages and dilated tortuous retinal vasculature are classic findings in the affected retina, and in severe cases, cotton-wool spots may be present (Fig 6-5). In acute disease, the level of visual acuity impairment depends on the severity of the macular ischemia or edema and the presence of intraretinal hemorrhages affecting the fovea. Macular edema is best assessed with spectral-domain optical coherence tomography (SD-OCT), while ischemia is best detected using fluorescein angiography or OCT angiography. Without treatment, increasing amounts of ischemic retina confer increasing risk for neovascularization. In patients with BRVO, neovascularization most commonly occurs in the healthy retina at the border of the affected, ischemic retina or, less commonly, at the optic nerve head, and, in rare instances, in the anterior segment. In patients with CRVO, neovascularization occurs most commonly in the anterior segment, manifesting as iris or angle neovascularization, but can also occur in in the retina or at the optic nerve head. Because anterior segment neovascularization is found in both branch and central retinal vein occlusions, periodic, undilated examinations of the iris and gonioscopic angle is recommended for all patients with RVO.
Improvement or spontaneous resolution can occur in patients with RVO. Improvement is usually associated with the development of adequate collateral blood flow. In BRVO, capillaries extending across the median raphe dilate, helping to compensate for the compromised venous drainage. In CRVO, small vessels that normally connect the retinal circulation to the choroidal circulation near the optic nerve head expand, resulting in the undulating appearance of optociliary shunt vessels. These mechanisms redirect venous drainage to the choroid, vortex veins, and superior and inferior ophthalmic veins in the orbit, bypassing the occluded central retinal vein. Chronic, untreated venous occlusive disease commonly leads to development of retinal microvascular changes characterized by microaneurysms, telangiectasias, and macular edema (Fig 6-6).
Figure 6-5 Branch retinal vein occlusion (BRVO) with ischemia. A, Fundus photograph shows inferotemporal BRVO. B, Fluorescein angiography image corresponding to A reveals pronounced retinal capillary nonperfusion in the distribution of the retina drained by the obstructed vein. C, Spectral-domain optical coherence tomography (SD-OCT) image of the same eye reveals cystoid macular edema (CME).
(Courtesy of Neal H. Atebara, MD.)
Anti–vascular endothelial growth factor (VEGF) drugs are mainstay of RVO treatment because of their excellent efficacy and safety profiles. Best visual acuity outcomes are achieved by administering anti-VEGF treatment immediately upon diagnosis of RVO-related macular edema. Anti-VEGF treatment also suppresses neovascular complications of RVO. Intraocular steroid treatments and macular or scatter panretinal photocoagulation are also employed to manage vision loss from, and complications of, RVO.
Specific considerations for branch and central retinal vein occlusion are discussed in the following sections.
Goldman DR, Shah CP, Morley MG, Heier JS. Venous occlusive disease of the retina. In: Yanoff M, Duker JS, eds. Ophthalmology. 4th ed. Philadelphia: Elsevier/Saunders; 2014: 526–534.
Hayreh SS. Retinal vein occlusion. Indian J Ophthalmol. 1994;42(3):109–132.
Branch Retinal Vein Occlusion
In BRVO, obstruction of the vein occurs most commonly at an arteriovenous crossing, where thickening of the arterial wall compresses the adjacent vein within a common adventitial sheath. When the occlusion does not occur at an arteriovenous crossing, the possibility of an underlying retinochoroiditis or retinal vasculitis should be considered. The quadrant most commonly affected is the superotemporal (63%); a clinical finding of nasal vascular occlusion is rare. The artery serving the area of venous occlusion may become narrowed and sheathed over time.
Figure 6-6 Chronic changes from nonischemic central retinal vein occlusion (CRVO) in a 30-year-old woman with a history of diabetes mellitus and blurry vision for 2 months. Visual acuity is 20/25. A, Color fundus photograph of a mild nonischemic, or perfused, CRVO. Dilated retinal veins and retinal hemorrhages are present, as are scant macular exudates inferior to fovea. B, Fluorescein angiography image taken 22 seconds after injection reveals capillary telangiectasias and microaneurysms throughout the posterior pole. C, Late angiogram taken at 9 minutes reveals diffuse retinovascular leakage and microaneurysms. D, OCT scan reveals mild cystic changes and microaneurysms but minimal retinal thickening and normal foveal contour.
(Courtesy of Neal H. Atebara, MD.)
Risk factors for the development of BRVO
The mean age of patients at the time of occurrence is in the seventh decade. The EDCC and other studies have identified the following risk factors for the development of BRVO:
Other studies have disputed the role of smoking or glaucoma as risk factors for BRVO. Diabetes mellitus was not a major independent risk factor in the EDCC, although 10%–12% of patients with RVO have the disease.
Prognosis for patients with BRVO
In acute disease, the presence or absence of macular or foveal involvement determines the visual prognosis. Prior to the availability of pharmacologic intervention, the Branch Vein Occlusion Study (BVOS) found that the incidence of neovascularization from the retina or optic nerve was 36% in eyes with extensive retinal ischemia; extensive ischemia was defined as an area of at least 5 disc diameters in size. Vitreous hemorrhage developed in 60%–90% of such eyes if laser photocoagulation was not performed.
Over the long term, permanent vision loss may be related to macular ischemia, cystoid macular edema (CME), lipid residues (hard exudates) in the fovea, pigmentary macular disturbances, subretinal fibrosis, and epiretinal membrane formation. Less common causes of vision loss include vitreous hemorrhage, tractional retinal detachment, and rhegmatogenous retinal detachment (RRD). RRD typically develops following a break in retina adjacent to, or underlying retinal neovascularization induced by vitreous traction.
Treatment of BRVO
Pharmacologic management Pharmacologic management is currently the mainstay of RVO management. See the section Pharmacologic Management of Retinal Vein Occlusion for a discussion of this topic.
Surgical management of BRVO
MACULAR LASER SURGERY
Laser grid photocoagulation may be applied to areas of macular edema caused by the obstructed vein (Fig 6-7). The BVOS found that laser-treated eyes with intact foveal vasculature, macular edema, and visual acuity in the 20/40–20/200 range were more likely to gain 2 lines of visual acuity (65%) than untreated eyes (37%). At 3-year follow-up, treated eyes were more likely to have 20/40 or better visual acuity than untreated eyes (60% vs 34%, respectively), with a mean visual acuity improvement of 1.3 ETDRS (Early Treatment of Diabetic Retinopathy Study) lines versus 0.2 line, respectively. In the BVOS, laser treatment of macular edema was delayed for at least 3 months to permit the maximum spontaneous resolution of intraretinal blood and the edema. While this practice may still be appropriate for macular laser therapy, treatment with pharmacologic agents should commence immediately upon diagnosis of BRVO.
The BVOS showed that scatter photocoagulation to the area of retinal capillary nonperfusion is effective in causing regression of the new vessels in eyes with retinal, optic nerve head, or iris neovascularization (Fig 6-8); it also reduced the risk of vitreous hemorrhage from 60% to 30%. Although the BVOS showed that patients with large areas of nonperfusion (see Fig 6-5) were found to be at significant risk of developing neovascularization, the study concluded that ischemia alone was not an indication for treatment, provided that follow-up could be maintained.
Figure 6-7 BRVO. A, Fundus photograph of inferotemporal BRVO. Corresponding fluorescein angiography images show, at 49 seconds after injection (B), telangiectatic vessels in the distribution of the inferotemporal vein, and at 393 seconds after injection (C), intraretinal leakage of dye from the capillaries in macular distribution of the vein occlusion (white). D, Fundus photograph after treatment shows a grid of macular photocoagulation lesions in the affected area but sparing the foveal region.
(Courtesy of Gary C. Brown, MD.)
Figure 6-8 BRVO with neovascularization. A, Neovascularization of the optic nerve head occurring secondary to a superotemporal BRVO. B, Corresponding fluorescein angiography image taken 18 seconds after injection reveals marked hyperfluorescence of the new vessels originating on the optic nerve head.
(Courtesy of Gary C. Brown, MD.)
Clinically, it is important to distinguish neovascularization of the optic nerve head or retina from collateral vessels, which have a larger caliber and do not leak when viewed with fluorescein angiography. Neovascularization of the iris occurs in approximately 2% of eyes with BRVO. In these cases, scatter laser photocoagulation in the distribution of the occluded vein should be considered to prevent the development of neovascular glaucoma.
Fuller JJ, Mason JO III. Retinal vein occlusions: update on diagnostic and therapeutic advances. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 2007, module 5.
PARS PLANA VITRECTOMY
Vitrectomy may be indicated for eyes that develop vitreous hemorrhage or retinal detachment (also see Chapters 16 and 20 in this volume).
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.