What is the differential diagnosis for a 70-year-old man with hypertension (high blood pressure) and hyperlipidemia (elevated lipid levels) who presents with sudden, painless vision loss in one eye, a history of transient vision loss, and reduced vision to only light perception?

Differential Diagnosis for Sudden Painless Monocular Vision Loss

This patient most likely has central retinal artery occlusion (CRAO), which is an acute ischemic stroke equivalent requiring immediate emergency department evaluation. 1 The history of prior transient vision loss two weeks earlier represents a retinal transient ischemic attack (TIA), and the current presentation with vision reduced to light perception indicates complete retinal infarction. 2

Primary Differential Diagnoses

Vascular Causes (Most Likely)

Central Retinal Artery Occlusion (CRAO)

• Sudden, painless monocular vision loss with profound visual impairment (light perception only) is the hallmark presentation 1
• Prior transient monocular vision loss (TMVL) two weeks ago represents a warning event—up to 10% of TMVL patients develop stroke within 90 days, with half occurring in the first 48 hours 3
• In 95% of cases, CRAO results from thromboembolic disease; patient's hypertension and hyperlipidemia are major risk factors 1
• Up to 40% of CRAO patients have ≥70% ipsilateral carotid stenosis 1
• Up to 25% have concurrent silent brain infarction on MRI 4, 5
• Natural history is devastating: only 17% achieve functional visual acuity in the affected eye 1

Branch Retinal Artery Occlusion (BRAO)

• Less likely given the severity (light perception only), as BRAO typically causes sectoral rather than complete vision loss 2, 4
• Would present with corresponding visual field defect rather than near-total vision loss 6

Arteritic Cause (Critical to Rule Out)

Giant Cell Arteritis (GCA) with Arteritic CRAO

• Accounts for 5% of CRAO cases 1
• Must be considered urgently in any patient over 50 years with sudden vision loss 4, 5
• Key symptoms to assess: jaw claudication (most specific, likelihood ratio 4.90), scalp tenderness, temporal artery tenderness, new headache, constitutional symptoms 4, 5
• ESR >60 mm/h has high likelihood ratio for diagnosis 4, 5
• Requires immediate high-dose IV corticosteroids before biopsy confirmation to prevent bilateral blindness 4, 5

Optic Nerve Causes

Anterior Ischemic Optic Neuropathy (AION)

• Can present with sudden painless vision loss 1, 7
• Non-arteritic AION: associated with hypertension, diabetes, hyperlipidemia—all present in this patient 7
• Arteritic AION: component of GCA, requires immediate steroid therapy 4
• Fundoscopic examination shows optic disc edema and pallor rather than retinal whitening seen in CRAO 1

Posterior Ischemic Optic Neuropathy

• Less common, typically associated with severe hypotension or surgical blood loss 8
• Normal fundus examination initially, making diagnosis challenging 8

Other Vascular Causes

Ophthalmic Artery Occlusion

• More severe than CRAO, affects both retinal and choroidal circulation 1
• Presents with complete vision loss and may have associated ocular pain 1

Retinal Vein Occlusion (Central or Branch)

• Less likely given the acute presentation and prior transient episode 6
• Typically presents with hemorrhages and venous tortuosity on fundoscopy, not the pale retina of arterial occlusion 6
• Associated with hypertension and hyperlipidemia but usually has better initial visual acuity 6

Non-Vascular Causes (Less Likely Given History)

Retinal Detachment

• Would present with floaters, flashes, and curtain-like visual field defect 1
• Painless but typically not associated with prior transient episodes 1

Vitreous Hemorrhage

• Sudden vision loss but patient would report "red haze" or floaters 6
• Associated with diabetic retinopathy, trauma, or retinal tears 6

Optic Neuritis

• Typically affects younger patients (20-40 years) 4
• Usually painful with eye movement 4
• Vision loss develops over hours to days, not instantaneously 4

Critical Diagnostic Pitfalls

Do not delay emergency evaluation for ophthalmologic examination 2, 5

• Eye care providers should serve as "gate-keepers" for rapid diagnosis, then immediately refer to stroke center 2
• Do not attempt further testing in the office—send directly to emergency department with note stating "Ocular Stroke" 2

Do not assume vision improvement eliminates stroke risk 4

• Stroke risk remains highest in first 7 days even if vision improves 4
• The prior transient episode indicates this patient is at extremely high risk for completed stroke 3

Do not miss giant cell arteritis 4, 5

• Check ESR and CRP in all patients over 50 years, regardless of whether classic symptoms are present 4, 5
• Start empiric steroids immediately if GCA suspected—do not wait for biopsy 4, 5

Recognize this as a stroke equivalent requiring stroke protocol 1, 2

• CRAO conforms to the definition of acute ischemic stroke per American Heart Association 1
• Patient needs brain MRI with diffusion-weighted imaging, vascular imaging (CTA or MRA from aortic arch to vertex), and cardiac monitoring within 24 hours 2, 3, 5
• Hospitalization is reasonable given presentation within 72 hours and recurrent episodes (crescendo pattern) 2