Acute Glaucoma

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Mechanism: Acute angle-closure glaucoma (ACG) is driven by the sudden narrowing or complete closure of the anterior chamber angle.
• The Breakdown: Aqueous humor normally drains out of the anterior chamber via the canal of Schlemm. When this drainage pathway is mechanically impeded, intraocular pressure (IOP) rapidly spikes from a normal baseline of 10–21 mm Hg up to 50–70 mm Hg.
• The Triggers: This emergency classically occurs in long-sighted, middle-aged, or elderly individuals who possess anatomically shallow anterior chambers. The acute blockage is frequently precipitated by pupil dilation, such as reading in dim light at night or the administration of anticholinergic medications.
• The Consequence: The acute pressure spike leads to corneal edema (causing blurred vision and haloes) and subsequent ischemic damage to the optic nerve, threatening permanent visual loss.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

Acute angle-closure glaucoma is a time-sensitive ocular emergency requiring an immediate polydrug regimen to lower IOP and emergent ophthalmology consultation.

• Immediate Resuscitation & Monitoring:
• Secure IV access, elevate the head of the bed, and administer systemic analgesia (e.g., IV morphine) and antiemetics to control pain and vomiting.
• Measure the IOP every 60 minutes to strictly monitor the response to therapy.
• The Polydrug Regimen (Aqueous Humor Suppressants & Miotics):
• Topical Beta-Blocker: Timolol 0.5%, 1 drop every 5–15 minutes. Action: Compress the medial canthus during administration to minimize systemic absorption.
• Topical Alpha-Agonist: Apraclonidine 1% or Brimonidine, 1 drop.
• Topical Carbonic Anhydrase Inhibitor: Dorzolamide 2%, 1 drop.
• Topical Miotic: Pilocarpine 4%, 1 drop every 15 minutes to force ciliary muscle contraction and open the drainage angle.
• Prophylaxis: Instill Pilocarpine 1% drops into the unaffected contralateral eye to prevent bilateral closure.
• Systemic Osmotic & Diuretic Therapy:
• IV Carbonic Anhydrase Inhibitor: Acetazolamide 500 mg IV.
• Osmotic Diuretic: Mannitol 20% (up to 500 mL) IV over 1 hour.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Critical "Can't-Miss" Differentials:
• Anterior Uveitis (Iritis): Presents with pain, photophobia, cell and flare in the anterior chamber, and a miotic (constricted) pupil, rather than a dilated one.
• Endophthalmitis & Keratitis: Deep space or corneal infections that present with a red, painful eye and often purulent discharge or hypopyon.
• Hyphema: Blood in the anterior chamber, typically following trauma, which can mechanically clog the canal of Schlemm and secondarily cause angle-closure glaucoma.
• Scleritis: Severe, boring eye pain with deep injection.
• Prioritized Workup:
• Visual Acuity: Must be documented for all patients presenting with an ocular complaint.
• Tonometry: The gold-standard bedside test to quantitatively measure IOP.
• Slit Lamp Examination with Fluorescein: Essential to evaluate the cornea for edema, rule out ulcerations, and assess the anterior chamber depth and presence of cell/flare.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

When assessing the patient at the bedside, look for this classic visual constellation:

• The Cornea: Appears distinctly hazy, "steamy," and edematous.
• The Pupil: Classically described as a fixed, semi-dilated, and ovoid (mid-size) pupil.
• The Sclera/Conjunctiva: Prominent circumcorneal erythema (limbal injection).
• Palpation: Through the closed upper eyelid, the affected globe feels distinctly hard and tender compared to the normal eye.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

While there is no complex scoring system (like HEART or PERC) for this condition, clinical decision-making is strictly driven by Tonometry cutoffs:

• Normal IOP: 10 to 21 mm Hg.
• Treatment Threshold: Initiation of the aggressive IOP-lowering medication regimen is indicated when IOP is > 30 mm Hg in the setting of compatible symptoms.
• Diagnostic Cutoff for ACG: Acute angle-closure glaucoma typically presents with an IOP > 40 mm Hg, frequently reaching 50 to 70 mm Hg. Patients with elevated IOP must be excluded from Clinical Decision Unit (CDU) observation pathways and require definitive admission/intervention.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Trap: Missing the Sickle Cell Exception: Administering IV Acetazolamide to a patient with sickle cell disease or trait is dangerous. In these specific patients, you must substitute with Methazolamide 50 mg PO.
• Trap: The Systemic Beta-Blocker Effect: Administering topical Timolol without compressing the medial canthus can lead to rapid systemic absorption, precipitating a severe asthma or COPD exacerbation.
• Trap: Misdiagnosing as a Primary GI or Neurologic Event: Because patients frequently present with prominent frontal headaches, severe nausea, and vomiting, trainees often misdiagnose the patient with a migraine or gastroenteritis, completely missing the underlying ocular catastrophe.
• Critical Action: You must document visual acuity and secure an immediate ophthalmology consultation; this is a time-sensitive, sight-threatening emergency that cannot be managed by emergency medicine alone.

7. MCQ MASTERCLASS (Written Exam Tips)

• The Classic "Buzzwords": Look for a patient describing "haloes around lights" or sudden eye pain triggered by "entering a dark room" or "reading in dim light" (events that cause physiological mydriasis). The physical exam will inevitably describe a "hazy/steamy cornea" and a "fixed, mid-dilated pupil".
• The Distractor Trap: Exam stems will frequently try to confuse Acute Glaucoma with Central Retinal Artery Occlusion (CRAO). Remember: CRAO presents with painless monocular vision loss and a "cherry red spot" on a pale retina. Acute glaucoma is extremely painful with a "red eye".

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

When presenting to the examiner, use this precise script:
"I am evaluating a 65-year-old patient presenting with acute-onset, severe, painful monocular vision loss, accompanied by frontal headache, nausea, and vomiting. On my physical exam, I have documented a decreased visual acuity. The affected eye demonstrates a hazy cornea, limbal injection, and a fixed, mid-dilated pupil. Palpation reveals a rock-hard globe, and bedside tonometry confirms an intraocular pressure of 55 mm Hg. My definitive diagnosis is Acute Angle-Closure Glaucoma. My critical actions include immediate ophthalmology consultation, administering IV analgesia and antiemetics, and initiating a targeted polydrug regimen: I will apply topical Timolol with medial canthus compression, topical Apraclonidine, Pilocarpine 4% to the affected eye, and Pilocarpine 1% prophylactically to the unaffected eye. I will also administer IV Acetazolamide and prepare a Mannitol infusion while monitoring IOP every 60 minutes."