Criteria

RVO is usually classified by the location of the occlusion.[4]​ Exam and investigation findings vary by location of occlusion as follows:

Central retinal vein occlusion (CRVO):

  • Four quadrants of retinal hemorrhages, vascular tortuosity and dilation, and retinal thickening

  • Optic nerve head edema

  • Delayed central retinal venous filling on fluorescein angiogram.

Branch retinal vein occlusion (BRVO):

  • One quadrant of retinal hemorrhage, vascular tortuosity and dilation, and retinal thickening

  • Delayed branch retinal venous filling on fluorescein angiogram.

Hemiretinal vein occlusion (HRVO):

  • Retinal hemorrhages, vascular tortuosity and dilation, and retinal thickening limited to superior or inferior retinal hemisphere

  • Optic nerve head edema may be present

  • Delayed filling of superonasal and superotemporal or inferonasal and inferotemporal retinal veins on fluorescein angiogram.

Ischemic/nonperfused versus nonischemic/perfused RVO

Ischemic CRVO is associated with:​ the presence of ≥10 disk areas of nonperfusion on 7-field fluorescein angiography and usually ≥1 of the following:[26]

  • Poor visual acuity (<6/60)

  • Relative afferent pupillary defect

  • Multiple dark deep intraretinal hemorrhages

  • Multiple cotton wool spots

  • Retinal vein tortuosity and dilation

  • Reduced b-wave amplitude, reduced b:a ratio and prolonged b-wave implicit time on electroretinogram.

In BRVO the degree of nonperfusion is important to guide treatment and prognosis:[4]

  • Nonperfused: presence of ≥5 disk areas of nonperfusion as assessed by fluorescein angiography.

  • Perfused: presence of <5 disk areas of nonperfusion.

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