What are the potential causes of abrupt vision loss in one eye?

Abrupt Vision Loss in One Eye: Potential Causes

Abrupt monocular vision loss is a medical emergency requiring immediate evaluation for vascular, inflammatory, and structural causes, with retinal artery occlusion and giant cell arteritis being the most time-critical diagnoses that demand urgent stroke center referral and empiric steroid treatment respectively. 1, 2

Vascular Causes (Most Time-Critical)

Retinal Artery Occlusion

• Central retinal artery occlusion (CRAO) is an ocular stroke equivalent requiring immediate stroke center transfer within 4.5 hours for potential thrombolysis. 1, 2, 3
• Branch retinal artery occlusion (BRAO) causes sectoral vision loss and requires urgent stroke evaluation within 24 hours. 2
• Up to 25% of CRAO patients have concurrent silent brain infarction on MRI, and up to 70% have significant carotid stenosis. 2
• Risk factors include cardiovascular disease, hypertension, diabetes, hyperlipidemia, and smoking. 2, 4
• Never assume reperfusion eliminates stroke risk—stroke risk remains highest in the first 7 days even if vision improves. 2

Transient Monocular Vision Loss (Amaurosis Fugax)

• Represents a retinal TIA with sudden, painless vision loss lasting seconds to minutes that resolves completely. 1, 2
• Stroke risk is maximum within the first few days after onset, requiring immediate stroke center referral without delay. 1, 2
• Do not perform extensive ophthalmologic workup before stroke center referral if vascular etiology is suspected. 2

Retinal Vein Occlusion

• Presents with painless vision loss, often less acute than arterial occlusion. 2
• Associated with hypertension, diabetes, hyperlipidemia, and hypercoagulable states. 2

Inflammatory/Arteritic Causes

Giant Cell Arteritis (GCA)

• Must be considered in all patients over 50 years with sudden vision loss. 2, 4
• Jaw claudication is the most specific symptom (likelihood ratio 4.90), followed by scalp tenderness, temporal tenderness, headaches, and constitutional symptoms. 1, 2, 4
• ESR >60 mm/h has high likelihood ratio for diagnosis. 1, 2
• Never delay empiric high-dose steroids for biopsy—start immediately in suspected cases to prevent vision loss in the contralateral eye. 2, 4
• Temporal artery biopsy should be performed after steroid initiation. 4

Optic Nerve Causes

Optic Neuritis

• Can be painless in approximately 8% of cases, though typically presents with pain on extraocular movements. 2, 4
• Features color desaturation and relative afferent pupillary defect (RAPD). 4
• Associated with multiple sclerosis, neuromyelitis optica, or other demyelinating conditions. 5, 2
• MRI of orbits and brain with contrast evaluates for optic nerve enhancement and intracranial demyelinating lesions. 5
• Treatment requires high-dose steroids and evaluation for multiple sclerosis. 4

Ischemic Optic Neuropathy

• Can be arteritic (from GCA) or non-arteritic. 4, 6
• Presents with painless vision loss and optic disc edema on fundoscopy. 6

Retinal Structural Causes

Retinal Detachment

• Presents with curtain-like visual field defect, often preceded by floaters and photopsias. 4
• Usually requires surgical intervention. 4
• Ultrasonography is useful for assessment when direct visualization is limited. 2

Vitreous Hemorrhage

• Causes sudden painless vision loss with obscured fundus view. 5, 6
• Associated with diabetic retinopathy, retinal tears, or trauma. 6

Acute Angle-Closure Glaucoma

• Features ocular pain, headache, nausea, and mid-dilated fixed pupil—distinguishing it from other painless causes. 4
• Treatment includes pilocarpine eye drops, oral or intravenous acetazolamide, and intravenous mannitol. 4

Critical Diagnostic Approach

Immediate Assessment

• Document visual acuity with current correction as first priority. 3
• Assess for relative afferent pupillary defect (RAPD), which indicates significant retinal or optic nerve dysfunction. 3
• Evaluate pupil size, shape, and reactivity—slow or poorly reactive pupils suggest significant retinal or optic nerve pathology. 3
• Check red reflex bilaterally—any asymmetry indicates serious pathology. 3
• Perform fundus examination and visual fields by confrontation. 3

Urgent Imaging and Laboratory Tests

• Brain MRI with diffusion-weighted imaging identifies concurrent stroke in up to 24% of retinal vascular events. 1, 2
• Vascular imaging (CTA or MRA) assesses carotid stenosis. 1, 2
• ESR and CRP should be evaluated in all patients over 50 years to assess for giant cell arteritis, regardless of whether classic symptoms are present. 1, 2

Critical Management Pitfalls to Avoid

• If vascular etiology is confirmed or suspected, immediately refer to stroke center with note stating "Ocular TIA" or "Ocular Stroke" without performing additional testing. 2, 3
• Never underestimate cardiovascular risk—new significant cardiovascular conditions are discovered in up to 70% of CRAO patients. 2
• Always check inflammatory markers in patients over 50, even without classic GCA symptoms. 2