A leading cause of monocular vision loss, central retinal vein occlusion (CRVO) is most commonly caused by thrombosis of the central retinal vein, resulting in retinal edema and hemorrhage.
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Terminology
Occlusion of the central retinal vein is subclassified as ischemic and non-ischemic based on the presence or absence of capillary blood flow 5.
Instead of the central retinal vein, the occlusion may occasionally affect a venous tributary only, which is termed branch retinal vein occlusion (BRVO).
Epidemiology
Risk factors
Risk factors associated with central retinal vein occlusion include 7:
- hypertension
- diabetes mellitus
- hyperlipidemia
- vasculitides
- hypercoagulable states
- glaucoma
- compressive orbitopathies
Clinical presentation
Typically more subtle in presentation than occlusion of the central retinal artery, central retinal vein occlusion presents on a continuum from a mild alteration in visual acuity and subjective blurring to profound monocular vision loss. Funduscopic examination classically reveals tortuous, engorged retinal veins with diffuse hemorrhages throughout the fundus, often referred to colloquially as a "blood and thunder" appearance. Papilledema may also be observed.
Radiographic features
Ultrasound
Spectral and color flow Doppler allow non-invasive examination of the retinal vasculature. Color flow Doppler is used to identify the location of the retrobulbar vessels, with subsequent pulsed wave Doppler interrogation of each flow signal. The central retinal vein may be identified as follows:
- color flow Doppler interrogation of the distal optic nerve reveals central paired vessels, representing the central retinal artery and vein
- pulsed wave Doppler may be used to simultaneously interrogate both vessels:
- the flow below the baseline, coursing away from the probe, corresponds to the central retinal vein
- flow is typically continuous with post-systolic peaks at fixed intervals from the systolic peak of the central retinal artery waveform
- the normal maximum velocity in the central retinal vein (CRV) may range from 2.9 to 5.7 cm/s 4
Sonographic features suggestive of central retinal vein occlusion include:
- decrease in the peak systolic and end diastolic velocities of the ipsilateral ophthalmic and central retinal artery 2
- concomitant increase in the resistive indices of both vessels
- this finding may be limited to the ischemic variant of central retinal vein occlusion
- decreased venous flow velocity in the central retinal vein
- a decrease in the maximum and minimum venous velocities may be present in severe cases
- a minimum venous velocity of less than 2 cm/s may be indicative of non-ischemic variants of central retinal vein occlusion 3