What are the differential diagnoses for left-sided eye pain accompanied by vomiting?

Differential Diagnosis for Left-Sided Eye Pain and Vomiting

Acute angle-closure crisis (AACC) is the most critical diagnosis to rule out immediately when a patient presents with unilateral eye pain and vomiting, as this represents a vision-threatening emergency requiring urgent treatment within hours. 1

Primary Differential Diagnoses

Vision-Threatening Emergencies (Rule Out First)

Acute Angle-Closure Crisis (AACC)

• Classic presentation: unilateral eye pain, headache, nausea/vomiting, blurred vision with halos around lights
• Physical findings: mid-dilated pupil, corneal edema, conjunctival/episcleral injection, markedly elevated intraocular pressure (IOP)
• Requires immediate IOP measurement and gonioscopy
• Treatment must begin within hours: aqueous suppressants, parasympathomimetics, osmotic agents, followed by laser iridotomy 1

Ruptured Cavernous Carotid Aneurysm with Carotid-Cavernous Fistula

• Can initially present as benign headache with vomiting, then rapidly progress to swollen, bloodshot eye within 24 hours
• Key findings: sudden onset headache, progressive chemosis (especially temporal and lower conjunctiva), lid erythema, enlarged ophthalmic veins, limited eye movements
• Requires urgent CT angiography and neurovascular intervention 2

Cerebral Venous Sinus Thrombosis (CVST) with Papilledema

• Bilateral vision loss with headache and vomiting
• Findings: bilateral disk edema, sluggish pupils
• Requires brain imaging with venography
• Can occur in hypercoagulable states (including post-COVID) 3

Other Serious Neurologic Causes

Posterior Circulation Stroke

• May present with eye pain, vomiting, and cranial nerve palsies
• Consider in patients with vascular risk factors or hypercoagulable states 3

Increased Intracranial Pressure

• Headache, vomiting, visual disturbances
• Examine for optic disc edema, cranial nerve VI palsy

Ophthalmologic Causes

Central Retinal Vein Occlusion (CRVO)

• Can occur after violent vomiting (Valsalva mechanism)
• Typically painless vision loss, but vomiting may precede or accompany
• Findings: retinal hemorrhages, dilated tortuous veins 4

Orbital Inflammation/Infection

• Pain with eye movement, proptosis, chemosis
• May cause nausea/vomiting from severe pain

Primary Headache Disorders

Migraine with Ophthalmic Features

• Unilateral headache, nausea/vomiting, photophobia
• Eye appears normal on examination
• Diagnosis of exclusion after ruling out structural causes 5

Cluster Headache

• Severe unilateral periorbital pain, lacrimation, conjunctival injection
• Less commonly associated with vomiting

Critical Examination Elements

Immediate assessments required:

• Intraocular pressure measurement (elevated in AACC, normal in most other causes)
• Pupil examination (mid-dilated and poorly reactive in AACC, RAPD in optic neuropathy)
• Red eye pattern (circumcorneal injection in AACC, diffuse in carotid-cavernous fistula)
• Optic disc examination (edema suggests papilledema, CVST, or optic neuropathy)
• Cranial nerve function (CN III, IV, VI palsies suggest cavernous sinus pathology)
• Gonioscopy (if IOP elevated, to confirm angle closure) 1

Diagnostic Algorithm

1. Measure IOP immediately - If elevated (>21 mmHg) with appropriate clinical picture → treat as AACC
2. Assess pupil and cornea - Mid-dilated pupil + corneal edema → AACC
3. Check for red eye - Pattern of injection guides localization
4. Examine optic disc - Edema requires neuroimaging for CVST, mass lesion
5. Assess eye movements - Limitation suggests orbital/cavernous sinus pathology
6. Neuroimaging if:
   • Sudden severe headache ("thunderclap")
   • Progressive symptoms over hours
   • Abnormal neurologic examination
   • Optic disc edema
   • Cranial nerve deficits

Common Pitfalls

• Dismissing as migraine without measuring IOP - AACC can be misdiagnosed as migraine, leading to permanent vision loss 2
• Assuming bilateral symptoms exclude unilateral pathology - CVST can present with bilateral findings but asymmetric onset 3
• Delaying imaging in "quiet eye" - Early or low-grade disease may not show obvious external signs 6
• Missing carotid-cavernous fistula - Symptoms can evolve rapidly from benign headache to orbital compartment syndrome within 8 hours 2

Any patient with unilateral eye pain and vomiting requires urgent ophthalmology evaluation if AACC cannot be definitively excluded, as treatment delay beyond 24 hours significantly worsens visual prognosis. 1