What could be causing transient blurry vision in one eye of a physically active adult, possibly between 20 and 50 years old, that occurs post-workout and resolves on its own?

Post-Workout Transient Monocular Blurry Vision

This presentation most likely represents exercise-induced transient corneal edema from endothelial dysfunction, though you must urgently rule out transient retinal ischemia (amaurosis fugax) which carries high stroke risk within 48 hours. 1, 2

Immediate Risk Stratification

The critical first step is distinguishing between two fundamentally different conditions:

High-Risk: Transient Monocular Vision Loss (Retinal Ischemia)

• Duration: Minutes (not seconds), described as a "shade" descending over vision 1, 2
• Mechanism: Retinal vascular ischemia from emboli or hypoperfusion 2, 3
• Urgency: Same cardiovascular event risk as transient brain ischemia; highest stroke risk within 48 hours 2
• Action required: Immediate stroke workup with brain DWI-MRI, vascular imaging (carotid ultrasound or CTA), cardiac evaluation, inflammatory markers (ESR/CRP to rule out giant cell arteritis), and stroke protocol 1, 2

Lower-Risk: Transient Visual Obscurations (Optic Nerve Ischemia)

• Duration: Seconds only (not minutes) 1
• Mechanism: Transient optic nerve head ischemia, typically from raised intracranial pressure 1
• Action required: IOP measurement, fundoscopy for papilledema, consider neuroimaging if papilledema present 1

Most Likely: Exercise-Induced Corneal Edema

• Duration: Minutes to hours, resolves spontaneously 4
• Mechanism: Endothelial dysfunction causing transient stromal edema during physiologic stress 4
• Characteristics: Blurred vision, often worse with humidity/heat, improves with evaporation and air movement 4

Diagnostic Approach

History Details to Elicit

• Exact duration: Seconds suggests transient visual obscurations; minutes suggests retinal ischemia; gradual onset/offset over minutes suggests corneal edema 4, 1
• Description: "Shade descending" = retinal ischemia; "dimming/darkening" = optic nerve ischemia; "blurring/fogging" = corneal edema 4, 1, 2
• Timing pattern: Worse upon waking or in humid environments suggests corneal edema from endothelial dysfunction 4
• Associated symptoms: Headache with TVOs suggests raised ICP; jaw claudication/temporal tenderness suggests giant cell arteritis 1, 2
• Vascular risk factors: Age >50, hypertension, diabetes, smoking, hyperlipidemia, carotid disease increase retinal ischemia likelihood 2, 5, 3

Physical Examination

• Slit-lamp biomicroscopy: Look for corneal stromal edema, endothelial changes (guttae suggesting Fuchs dystrophy) 4
• IOP measurement: Elevated IOP can cause acute corneal edema; also required in TVO workup 4, 1
• Dilated fundus exam: Check for emboli (Hollenhorst plaques), retinal whitening, optic disc edema (papilledema) 4, 1, 2
• Gonioscopy if IOP elevated: Rule out angle closure 4

Management Algorithm

If Duration is Minutes with "Shade" Description:

Treat as retinal ischemia emergency 2

• Immediate ophthalmology consultation 2
• Check ESR/CRP urgently (giant cell arteritis can cause permanent blindness) 2
• Initiate stroke protocol: aspirin, vascular imaging, cardiac workup 2, 3
• Admit or arrange urgent outpatient stroke prevention within 24-48 hours 2

If Duration is Seconds with Dimming:

Evaluate for raised intracranial pressure 1

• Fundoscopy for papilledema 1
• If papilledema present: neuroimaging (MRI brain with venography), neurology referral 1
• Consider idiopathic intracranial hypertension in young overweight females 1

If Gradual Blurring Resolving Over Minutes:

Most consistent with exercise-induced corneal edema 4

• Slit-lamp examination to confirm corneal edema and assess endothelium 4
• If mild endothelial dysfunction (early Fuchs dystrophy): counsel on benign nature, recommend avoiding high humidity during exercise, consider hypertonic saline drops (5% NaCl) if symptomatic 4
• If normal examination: reassure, but arrange follow-up if symptoms persist or worsen 4
• Avoid topical corticosteroids which can elevate IOP and worsen corneal edema 4

Critical Pitfalls to Avoid

• Assuming benign cause without ruling out retinal ischemia: Patients with retinal TIA have highest stroke risk within 48 hours; missing this diagnosis has catastrophic consequences 2
• Failing to check inflammatory markers in patients >50: Giant cell arteritis requires immediate high-dose corticosteroids to prevent permanent bilateral blindness 2
• Attributing symptoms to dehydration without examination: While exercise-related hypoperfusion can cause transient visual symptoms 5, this diagnosis requires excluding structural/vascular pathology 2
• Dismissing unilateral symptoms: Corneal edema from endothelial dysfunction is typically bilateral, though can be asymmetric; truly unilateral presentation increases suspicion for vascular or structural cause 4

When to Refer Urgently

• Any episode lasting minutes (not seconds) requires same-day ophthalmology evaluation and stroke workup 1, 2
• Age >50 with any transient vision loss: check ESR/CRP immediately for giant cell arteritis 2
• Papilledema on examination: urgent neuroimaging and neurology referral 1
• Recurrent episodes despite normal examination: consider provocative testing or extended monitoring 4