What is the most likely diagnosis for a patient presenting with sudden decrease in visual acuity, nausea, red eye, and a hazy cornea?

Acute Angle-Closure Crisis (Glaucoma)

The most likely diagnosis is acute angle-closure crisis (AACC), a sight-threatening emergency characterized by sudden IOP elevation causing the classic triad of decreased vision with corneal edema ("steamy" cornea), ocular pain with nausea/vomiting, and conjunctival injection (red eye). 1

Pathognomonic Clinical Features

The constellation of symptoms presented is diagnostic for AACC:

• Sudden decrease in visual acuity occurs from pressure-induced corneal edema, which creates the characteristic "steamy" or hazy corneal appearance 1, 2
• Nausea and vomiting are systemic manifestations of the acute IOP spike, often accompanied by severe headache 1
• Red eye results from conjunctival and episcleral vascular congestion secondary to markedly elevated IOP 1
• Corneal edema (the "steamy" cornea) is caused by endothelial dysfunction from IOP typically exceeding 40 mmHg 2, 3

Additional Examination Findings to Confirm Diagnosis

On examination, you should specifically look for:

• Mid-dilated, poorly reactive or fixed pupil in the affected eye (may appear oval or asymmetric) 1, 3
• Markedly elevated IOP (typically >40 mmHg, often 50-70 mmHg) 2, 3
• Shallow anterior chamber on slit-lamp examination 1
• "Boxcar" segmentation of blood flow in retinal vessels visible on fundoscopy 1
• Cherry red spot may be visible if there is concurrent retinal ischemia, though this is more typical of retinal artery occlusion 1

The American Academy of Ophthalmology emphasizes that immediate IOP measurement and pupil assessment are critical, as untreated eyes can become blind within hours. 2

Critical Differential Considerations

While AACC is the clear diagnosis here, be aware that:

• Central retinal artery occlusion presents with sudden painless vision loss (not painful), normal IOP, and no corneal edema 1
• Corneal ulcer causes sharp pain with foreign body sensation and visible epithelial defect on fluorescein staining, but IOP is normal 2
• Anterior uveitis has a small (not mid-dilated) pupil and normal or low IOP 2

Immediate Management Algorithm

The American Academy of Ophthalmology recommends immediate treatment without waiting for ophthalmology consultation: 2, 3

1. Start topical IOP-lowering therapy immediately:

   • Topical beta-blocker (timolol 0.5%)
   • Topical alpha-2 agonist (apraclonidine 1% or brimonidine)
   • Topical carbonic anhydrase inhibitor (dorzolamide or brinzolamide) 2, 3

2. Add systemic hyperosmotic agents:

   • Oral acetazolamide 500mg or IV if patient is vomiting
   • Oral glycerol or IV mannitol for rapid IOP reduction 2, 3

3. Definitive treatment once IOP controlled:

   • Emergent laser peripheral iridotomy (LPI) in the affected eye
   • Prophylactic LPI in the fellow eye (which has approximately 50% risk of acute attack within 5 years if untreated) 2, 3, 4

Critical Pitfalls to Avoid

• Do not delay treatment waiting for ophthalmology—18% of untreated eyes become blind within 4-10 years, and rapid glaucomatous optic neuropathy can occur within hours 2, 4
• Do not dilate the pupil in the fellow eye until after prophylactic LPI is performed, as dilation can precipitate acute crisis 2, 4
• Do not dismiss the fellow eye—it requires urgent prophylactic treatment as acute attacks can occur within days 3, 4
• Monitor for persistent IOP elevation after LPI, as some patients have plateau iris configuration requiring additional treatment 3

The natural history without treatment is devastating: 48% develop glaucomatous optic neuropathy and 58% have visual acuity worse than 20/40 within 4-10 years following AACC. 1