4.2 Branch Retinal Vein Occlusion

Fig. 4.1 A 74-year-old patient with an unambiguous, severely ischemic superior HCRVO and a simultaneous less ischemic inferior HCRVO. The yellow arrow denotes an arteriovenous shunt vessel that does not supply intervening capillaries that are closed. The red arrow denotes an analogous vessel that connects a superior arteriole with an inferior venule, an early manifestation of an intraretinal collateral vessel that shunts venous drainage to the less severely obstructed inferior venous system

tion.5 They developed a classification for RVOs that emphasizes local effects on the vein wall (Fig. 4.2). They contend that their classification more cleanly separates the RVOs by etiology and provides a more logical framework for analyzing risk factors.5 In their schema, the categories are arteriovenous crossing RVO, optic cup RVO, and optic nerve RVO. Arteriovenous crossing RVO would be called peripheral BRVO by many clinicians. The category optic cup RVO is a novel category that would correspond to a pooling of the more traditional categories of major BRVO and HCRVO in which the occlusion occurs at the cup. Optic nerve RVO is a novel category that would correspond to a pooling CRVO and HCRVO in which the occlusion occurs in the nerve. Optic nerve RVOs were further subdivided into a category without optic nerve head edema and another with optic nerve edema.

Many studies use the terms nonischemic and ischemic but fail to define what is meant.8,12,35,40,50,51 Others define the terms but use different

definitions.11,14,17,19,27,31,39,47,52,53 This makes it

difficult to compare results across studies.

To add to the complexity, ischemia can vary within different regions of the retina in a single patient (Fig. 4.1). With candor and accuracy, Binder and colleagues wrote, “The definitions for ischemic versus non-ischemic CRVO differ wildly in the literature,” and the same applies to BRVO and HCRVO.7

Beaumont and Kang have argued that site of occlusion is an important variable for categoriza-

4.2 Branch Retinal Vein Occlusion

BRVO is classified into major and macular types. Major BRVO (MJBRVO) involves a first-, second-, or third-order vein in which the macular involvement is not the greatest fraction of the involved retina (Fig. 4.3). Macular BRVO (MCBRVO) denotes an occlusion of a small vein draining a sector of the macula; the retina outside the posterior pole is not involved (Fig. 4.4).26,37 MCBRVO comprises 17–29% of cases of BRVO.26,30 Thereproducibilityofthisclassification has not been examined.

MJBRVO is further subclassified into nonischemic versus ischemic.43 Although the degree of

Fig. 4.4 An 81-year-old woman was seen with sudden onset of blurred vision of the left eye. The visual acuity of the left eye was 20/70. A macular BRVO with macular edema was present. (a) A color fundus photograph at the time of initial presentation shows a sector of intraretinal hemorrhage inferonasal to the fovea and involving three clock hours of the foveal avascular zone border. (b) A frame from the late fluorescein angiogram taken several

weeks later shows hypofluorescence corresponding to the intraretinal hemorrhage and some leakage of fluorescein obscured by the blood. (c) An OCT false-color map shows edema centered nasal to the fovea. (d) An OCT horizontal line scan shows superficial intraretinal blood (yellow arrow) that blocks visualization of the RPE and Bruch’s membrane complex (turquoise arrow)

Fig. 4.3 A 74-year-old man with primary open-angle glaucoma and a retinal vein occlusion. This case could be classified as a major BRVO using Hayreh’s system26 or could be classified as an optic cup-sited RVO using the system of Beaumont and Kang.5 Optic cup-sited RVOs had the strongest association with primary open-angle glaucoma of any type of RVO.5,6 (a) Monochromatic fundus photograph showing a sector of intraretinal hemorrhages in the superotemporal quadrant. (b) Magnified monochromatic photograph of the optic disc. Glaucomatous cupping is present, as is a peripapillary zone of retinal pigment epithelial atrophy. The site of the vein occlusion is not at the arteriovenous crossing (green arrow). Instead, the site of the occlusion is at the rim of the optic cup (red arrow) as manifested by the venous dilation proximal to the arterio-

venous crossing but colocalized with the rim of the optic disc cup. (c) By a fluorescein angiographic classification system, this branch vein occlusion is nonischemic. This frame from the mid-phase fluorescein angiogram shows that the perifoveal capillary border is intact and that capillary perfusion is present throughout the area of distribution of the retinal hemorrhages. It is, therefore, a nonischemic MJBRVO. (d) Frame from the late-phase fluorescein angiogram shows that the retinal vessels in the superotemporal macula leak fluorescein. (e) Optical coherence tomography from 10/29/2010 shows cystoid macular edema. The best corrected visual acuity was 20/50. The patient elected no treatment. The patient returned on 2/1/2011 with visual acuity reduced to 20/70 and with worsening of the macular edema on OCT