Epidemiology

Etiology

Retinal artery occlusion

• Embolism
  • Release of thrombotic emboli as a result of carotid artery atherosclerosis (most common)

Retinal vein occlusion

• Systemic diseases
  • Atherosclerosis
  • Hypertension
  • Diabetes mellitus

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.
• 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

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

Treatment