What is the differential diagnosis for a patient with intermittent cloudy vision and blackness when looking down?

Differential Diagnosis: Intermittent Cloudy Vision with Blackness When Looking Down

This presentation is most consistent with intermittent angle-closure glaucoma, which requires urgent ophthalmology referral for gonioscopy and prophylactic laser peripheral iridotomy to prevent permanent blindness. 1, 2

Vision-Threatening Emergency: Intermittent Angle-Closure Glaucoma

The combination of intermittent cloudy vision and positional symptoms (blackness when looking down) is pathognomonic for intermittent angle-closure episodes. 1 The cloudy vision results from pressure-induced corneal edema during transient intraocular pressure spikes, while the positional component suggests pupillary block that varies with eye position. 1, 2

Critical Risk Assessment

• Untreated patients have a 50% risk of acute angle-closure crisis within 5 years 1, 2, 3
• 18% of eyes become permanently blind and 48% develop glaucomatous optic neuropathy within 4-10 years following untreated acute crisis 1, 2, 3
• The intermittent nature represents warning episodes before potentially blinding acute attacks 1, 2

Key Clinical Features to Assess

• Halos around lights (caused by corneal edema from elevated IOP) 1
• Eye pain, headache, or pressure sensation during episodes 1, 3
• Nausea or vomiting with severe episodes 2
• Timing of symptoms (often occurs in dim lighting or after pupil dilation) 1
• Bilateral nature (strongly suggests primary angle closure disease) 1

Risk Factors to Identify

• Demographic: Female gender, Asian or Inuit ethnicity, age >50 years, family history 1, 3
• Ocular anatomy: Hyperopia, shallow anterior chamber, short axial length, thick anteriorly-positioned lens 1, 3

Mandatory Immediate Examination

• Intraocular pressure measurement by Goldmann applanation tonometry in both eyes 2, 3
• Pupil examination for mid-dilated, poorly reactive, or oval pupil shape 2, 3
• Slit-lamp assessment of anterior chamber depth 2
• Gonioscopy in a dark room to assess iridotrabecular contact and peripheral anterior synechiae (this confirms the diagnosis) 1, 3

Definitive Management

Laser peripheral iridotomy (LPI) is the definitive treatment once gonioscopy confirms iridotrabecular contact. 1 Both eyes require prophylactic treatment given the bilateral nature of primary angle closure disease. 1 Do not delay fellow eye prophylaxis, as acute attacks can occur within days. 1

Alternative Diagnoses to Consider

Retinal Vascular Occlusion (Branch or Central Retinal Artery Occlusion)

• Presents with sudden painless vision loss (not typically intermittent or positional) 4
• Requires immediate referral to stroke center within 72 hours due to high risk of concurrent cerebral infarction 4
• Look for vascular risk factors, embolic sources, and abnormal cardiac evaluation 4
• The positional component ("blackness when looking down") makes this less likely but warrants urgent evaluation if vision loss is present 4

Corneal Edema from Other Causes

• Fuchs endothelial dystrophy: Typically bilateral, worse in morning, improves with low humidity 4
• Visual acuity may not correlate with symptoms; patients may have 20/40 vision but disabling glare 4
• Contact lens-related edema: History of rigid gas-permeable lens wear 4
• Medication-induced: Amantadine, topical chlorhexidine exposure 4

Convergence Insufficiency

• Presents with eyestrain, headaches, blurred vision, diplopia at near 4
• Associated with exophoria at near, difficulty concentrating while reading 4
• Does not typically cause positional blackness or intermittent cloudy vision 4
• More common after concussion or in Parkinson's disease 4

Giant Cell Arteritis (in patients >50 years)

• Transient monocular vision loss with jaw claudication, scalp tenderness, constitutional symptoms 4
• Requires immediate empiric steroids if suspected to prevent vision loss in the unaffected eye 5
• Check ESR, CRP, and platelet count; arrange temporal artery biopsy 4, 5

Critical Pitfalls to Avoid

Do not dismiss transient symptoms as benign even if the patient is asymptomatic at presentation—these represent warning episodes before potentially blinding acute attacks. 1, 2

Avoid pupil dilation until after iridotomy is performed in patients with suspected narrow angles, as dilation can precipitate acute angle-closure crisis. 1, 2

Do not delay treatment waiting for ophthalmology consultation if acute angle-closure glaucoma is suspected during an active episode. 2

Immediate Action Algorithm

1. Measure IOP immediately in both eyes 2, 3
2. If IOP elevated (>21 mmHg) with symptoms: Treat as acute/intermittent angle closure with topical beta-blockers, alpha-2 agonists, carbonic anhydrase inhibitors, and consider oral/IV hyperosmotic agents 2
3. If IOP normal but symptoms suggestive: Urgent ophthalmology referral same-day for gonioscopy 1, 3
4. Assess for vision loss: If sudden vision loss present, refer immediately to stroke center 4, 2
5. If age >50 with systemic symptoms: Consider giant cell arteritis and check ESR/CRP emergently 4, 5