Introduction:

Central retinal vein occlusion (CRVO) is due to an obstruction of the central retinal vein at or proximal to the lamina cribrosa. The incidence of CRVO in the US is 30,000 per annum. Risk factors include age >55 years, a history of glaucoma, systemic hypertension, smoking, hyperlipidemia, diabetes, atherosclerosis, coagulopathies, vasculitis, and oral contraceptive use.

Clinical Features:

Dilated, tortuous retinal veins and intraretinal hemorrhages are noted in all four quadrants (Fig. 14.2.1). Cotton wool spots, disc edema and macular edema may also be seen. CRVO may be subdivided into ischemic or non-ischemic based on the degree of peripheral retinal non-perfusion seen on fluorescein angiography. Ischemic CRVO tend to have worse visual acuity (<20/200) and more confluent hemorrhage and cotton wool spots. Non-ischemic CRVO usually presents with better visual acuity and the relative paucity of cotton wool spots. Non-ischemic CRVO will convert to ischemic CRVO over weeks to months in about 20–30% of cases. Although the diagnosis of CRVO can be made by the characteristic fundus appearance, perfusion and the presence of ischemia is best assessed by a fluorescein angiogram.

OCT Features:

Macular edema, a critical feature of CRVO, is best evaluated by an OCT scan (Figs 14.2.2 and 14.2.3). A line scan through the macula shows diffuse thickening with hyporeflective spaces within the outer retinal layers consistent with cystoid macular edema. Some subretinal fluid may also be noted, which most likely is secondary to excess intraretinal fluid ‘overflowing’ into the subretinal space.

A macular cube scan shows diffuse thickening. Central subfield thickness on a cube scan as well as the topography of the edema on the macular map is an effective way of monitoring macular edema over serial visits as well as response to treatment and correlates well to visual acuity in non-ischemic CRVO.

Ancillary Testing:

Intravenous fluorescein angiography may show areas of blocked fluorescence from the intraretinal blood, staining of the vessel walls, a delayed arteriovenous phase, non-perfused areas and perifoveal leakage. In the early stages, the presence of hemorrhage may block fluorescence and make it difficult to assess for ischemia. Moreover, the fluorescein angiogram may not show the full extent of perifoveal leakage because of lack of intact perifoveal vessels. Neovascularization of the retina in CRVO will show diffuse leakage from abnormal blood vessels.

Treatment:

There is no known effective mechanism to treat macular ischemia in CRVO. However, macular edema may effectively be treated with intravitreal anti-VEGF agents such as bevacizumab, ranibizumab and aflibercept, as well as intravitreal triamcinolone and a sustained release fluocinolone steroid implant. Neovascularization in CRVO is treated with pan retinal photocoagulation laser. Anti-VEGF agents may also be used as adjuncts in the treatment of neovascularization secondary to CRVO.