What are transient retinal symptoms?

Transient Retinal Symptoms

Transient retinal symptoms, primarily known as transient monocular vision loss (TMVL) of vascular origin, represent retinal transient ischemic attacks (TIAs) that should be considered ocular and systemic emergencies requiring immediate diagnosis and treatment. 1

Definition and Classification

• TMVL of vascular origin is a retinal TIA, characterized by sudden, painless loss of vision in one eye that clears within seconds to minutes 1, 2
• TMVL is part of the spectrum of acute retinal arterial ischemia, which also includes branch retinal artery occlusion (BRAO) and central retinal artery occlusion (CRAO) 1
• These conditions reflect acutely impaired blood flow in the anterior cerebral and ocular circulation 1

Causes and Mechanisms

• Vascular TMVL is most commonly caused by embolic events, similar to cerebral TIAs 1, 2
• Other causes include:
  • Hemodynamic factors from carotid artery stenosis 1, 3
  • Central retinal artery vasospasm (usually benign) 1
  • Nonvascular ocular causes and migrainous visual aura (often misinterpreted as monocular) 1
• Specific presentations may include:
  • Classic amaurosis fugax (sudden vision loss that clears within minutes) 2
  • Bright-light amaurosis fugax (visual loss upon exposure to bright light) 2
  • Telescoping vision due to hemodynamic compromise 2

Clinical Significance

• TMVL is not benign but represents a serious condition on the spectrum of brain and eye ischemia 1
• The American Heart Association defines retinal cell death attributable to ischemia as a stroke equivalent 1
• While the risk of stroke after retinal TIA may be lower than after cerebral TIA, the overall risk for cardiovascular events and death remains similar 1
• The risk of stroke is maximum within the first few days after onset of visual symptoms 1

Pathophysiological Considerations

• Collateral circulation plays a major role in patients with carotid stenosis, with flow often diverted from the eye to the brain via the circle of Willis 1
• Small platelet-fibrin emboli may cause visual symptoms in the eye but might not produce noticeable neurological symptoms in the brain 1
• Visual symptoms are more readily perceived than brief neurological deficits because our eyes are constantly open when awake 1
• The "intraluminal streaming phenomenon" explains why recurrent vascular emboli tend to go to the same arterial branch 1

Diagnostic Approach

• Prompt and accurate diagnosis is essential due to the risk of subsequent stroke 1
• Guidelines recommend:
  • Urgent brain MRI with diffusion-weighted imaging 1
  • Vascular imaging 1
  • Clinical assessment to identify patients at highest risk for recurrent stroke 1

Management

• TMVL requires immediate referral to specialized stroke centers without delay 1
• Treatment should follow the same protocols as for cerebral TIAs 1
• Early preventive treatments are crucial to reduce the risk of subsequent stroke and cardiovascular events 1
• Collaboration among optometrists, ophthalmologists, and stroke neurologists is essential 1

Common Pitfalls

• Misdiagnosis of nonvascular causes as vascular TMVL is common 1
• Delayed referral and treatment due to the outdated belief that retinal ischemia is less concerning than cerebral ischemia 1
• Failure to recognize TMVL as a medical emergency requiring immediate evaluation 1
• Overlooking carotid artery stenosis or occlusion during initial evaluation 4

Remember that "time is retina" - just as in acute brain ischemia, prompt diagnosis and treatment of TMVL are essential to prevent permanent visual loss and reduce the risk of subsequent stroke 5.