A 58-year-old woman presents to the emergency department with acute onset severe eye pain, blurred vision, and haloes around lights in the right eye for the past 6 hours. On examination, the eye is red, cornea is hazy, and intraocular pressure is 58 mmHg. The anterior chamber appears shallow. Which investigation is most appropriate to confirm the diagnosis of primary angle-closure glaucoma before initiating emergency treatment?

Explanation

## Investigation of Choice for Acute Angle-Closure Glaucoma **Key Point:** Gonioscopy is the gold standard investigation to directly visualize the angle and confirm angle closure, making it the investigation of choice in suspected primary angle-closure glaucoma. ### Why Gonioscopy? Gonioscopy allows direct visualization of the anterior chamber angle and confirms: 1. **Angle closure** — appositional or synechial closure of the angle 2. **Peripheral iris configuration** — steep peripheral iris profile 3. **Trabecular meshwork status** — degree of angle obstruction 4. **Mechanism of closure** — pupillary block vs. non-pupillary block ### Clinical Context In acute angle-closure glaucoma, the clinical presentation is dramatic: - Severe eye pain and redness - Corneal edema (hazy cornea) - Markedly elevated IOP (typically > 40 mmHg) - Shallow anterior chamber on slit-lamp examination **High-Yield:** Gonioscopy is performed AFTER the acute attack is partially controlled (IOP lowered with medications) because corneal edema may initially obscure the view. However, it remains the definitive confirmatory test. ### Comparison with Other Investigations | Investigation | Role in PACG | Limitation | |---|---|---| | **Gonioscopy** | Direct angle visualization; confirms closure | Gold standard; requires clear media | | OCT (optic nerve) | Assesses optic nerve damage; used for monitoring | Does not visualize angle; shows structural damage only | | Visual field testing | Detects functional loss; used for follow-up | Unreliable in acute attack; not diagnostic | | Ultrasound B-scan | Useful if media opaque (dense cataract) | Indirect; does not visualize angle directly | **Clinical Pearl:** In the acute setting with corneal haze, if gonioscopy cannot be performed immediately, start medical therapy (topical beta-blockers, prostaglandin analogues, carbonic anhydrase inhibitors, and IV mannitol) to lower IOP and clear the cornea, then perform gonioscopy. [cite:Khurana Ophthalmology Ch 9]