| Feature | Retinal Artery Occlusion (RAO) | Retinal Vein Occlusion (RVO) |
|---|---|---|
| Patho | Arterial embolus (carotid, A-fib) → Ischemia | Venous thrombus (compression) → Hemorrhage |
| Presentation | Sudden, profound, painless vision loss (“curtain”) | Subacute, blurry, painless vision loss |
| Fundoscopy | Pale retina + cherry-red spot | ”Blood & Thunder” (widespread hemorrhages) |
| Key Risk Factors | Carotid stenosis, A-fib, GCA | HTN, DM, Glaucoma |
| Mgmt | EMERGENCY: Ocular massage, ↓IOP. R/o GCA. | Manage complications: Anti-VEGF (for edema) |
| Prognosis | Poor for vision | Variable; better than RAO |
Epidemiology
Etiology
Retinal artery occlusion
- Most common cause is carotid artery atherosclerosis.
- Other causes include cardiogenic emboli (e.g., from atrial fibrillation), and giant cell arteritis (GCA), especially in the elderly.
Retinal vein occlusion
- Caused by thrombosis of the central retinal vein or its branches, often due to compression by an adjacent atherosclerotic artery at an arteriovenous crossing.
- Leads to increased venous pressure, resulting in hemorrhage and fluid leakage into the retina.
- Strongly associated with systemic vascular risk factors like HTN, diabetes mellitus, hyperlipidemia, and glaucoma.
Pathophysiology
- In CRAO, arterial blockage causes ischemic cytotoxic edema as cells swell due to ATP depletion and ion pump failure. Because blood flow is prevented from entering the retina due to arterial blockage, there’s no pressure buildup to cause vessel rupture (hemorrhage).
- In CRVO, venous obstruction creates increased hydrostatic pressure behind the blockage, forcing blood to leak from damaged capillary walls and producing the characteristic widespread hemorrhages throughout the retina.
Clinical features
Retinal artery occlusion
- Central retinal artery occlusion (CRAO)
- Sudden, painless loss of vision in one eye (often described as a “descending curtain”)
- Ophthalmoscopic findings
- Grayish-white (cloudy) discoloration of the entire retina
- A result of edema within the nerve fiber layer (NFL)
- Cherry-red spot at the fovea centralis
- No nerve fibers are present in the foveal avascular zone (FAZ). Therefore, the FAZ is not affected by edema of the nerve fiber layer. The underlying choroid is clearly visible as a cherry-red spot against a dull white background.
- Grayish-white (cloudy) discoloration of the entire retina
- BRAO
- Sudden onset of visual field defects (scotomas) in the affected eye
- Ophthalmoscopic findings
- Grayish-white discoloration of the retinal quadrant supplied by the affected vessel
Retinal vein occlusion
- Ischemic CRVO
- Sudden, severe loss of vision in the affected eye
- Ophthalmoscopic findings
- Many dot-and-blot and/or flame-shaped hemorrhages in all four retinal quadrants and venous thickening (blood and thunder appearance)
- Cotton wool spots
- Characterized by yellow-white deposits on the retina
- Caused by swelling of retinal nerve fibers due to ischemia
- Severe macular edema
- Severe papilledema
- Many dot-and-blot and/or flame-shaped hemorrhages in all four retinal quadrants and venous thickening (blood and thunder appearance)
Diagnostics
Retinal artery occlusion
- Evaluation for cardiovascular risk factors:
- Carotid doppler (to look for atherosclerotic plaques)
- Echocardiography (to identify potential sources of emboli, e.g. cardiac vegetations, patent foramen ovale)
- Tests to rule out temporal arteritis:
- Inflammatory markers (e.g., ↑ ESR)
- Temporal artery biopsy
Tip
Retinal artery occlusion is also called ‘retinal stroke”; patients with retinal artery occlusion are at a significantly higher risk of having a stroke.