Which of the following is not a diagnostic test used to diagnose acute angle closure glaucoma?

Diagnostic Tests for Acute Angle Closure Glaucoma

Provocative testing is not a diagnostic test used to diagnose acute angle closure glaucoma, as it has been largely replaced by careful gonioscopic examination and synthesis of clinical findings. 1

Standard Diagnostic Tests for Acute Angle Closure Glaucoma

1. Slit-lamp Biomicroscopy

• Reveals key findings:
  • Conjunctival hyperemia in acute cases
  • Central and peripheral anterior chamber depth narrowing
  • Anterior chamber inflammation
  • Corneal edema (microcystic and stromal)
  • Iris abnormalities (atrophy, posterior synechiae, abnormal pupillary function)
  • Mid-dilated, poorly reactive pupil
  • Lens changes (cataract and glaukomflecken - patchy anterior subcapsular opacities)
  • Corneal endothelial cell loss 1

2. Intraocular Pressure Measurement

• Typically measured using Goldmann applanation tonometry
• Shows markedly elevated IOP, often >40-50 mmHg in acute cases
• Should be performed before gonioscopy 1

3. Gonioscopy

• Gold standard for diagnosis
• Evaluates angle anatomy, presence of iridotrabecular contact (ITC), and peripheral anterior synechiae (PAS)
• Compression (indentation) gonioscopy helps differentiate appositional from synechial closure
• Should be performed in dark room conditions with appropriate technique
• May require topical glycerin to clear corneal edema for better visualization 1

4. Anterior Segment Imaging

• Useful adjunct when gonioscopy is difficult or impossible
• Options include:
  • Anterior segment optical coherence tomography (AS-OCT)
  • Ultrasound biomicroscopy (UBM)
  • Scheimpflug imaging
• UBM provides better characterization of posterior iris and ciliary body compared to AS-OCT 1, 2

Why Provocative Testing Is Not Used

Provocative tests (such as dark-room prone positioning and pre/post-dilation IOP measurement) were historically used to identify patients at risk for angle closure. However, the American Academy of Ophthalmology guidelines clearly state that "careful gonioscopic examination and synthesis of the clinical findings have largely replaced the use of provocative tests to make therapeutic decisions for patients at risk for PAC." 1

In the Zhongshan Angle Closure Prevention trial, dark-room provocative testing was found to have limited clinical utility in predicting which eyes would develop angle closure 1. This has led to the abandonment of provocative testing in routine clinical practice for diagnosing acute angle closure glaucoma.

Clinical Pearls and Pitfalls

• Corneal edema pitfall: Gonioscopic visualization may be impaired by corneal edema. Use topical glycerin to temporarily clear the cornea for better angle visualization 1

• Examination technique: Perform gonioscopy in a dark room with a bright, short beam that doesn't pass through the pupil to avoid inducing pupillary constriction that can artificially widen the angle 1

• Biometric risk factors: Consider ocular biometry to identify risk factors such as short axial length (<20.0 mm), small horizontal corneal diameter (<11.0 mm), and high hyperopia 1, 3

• Secondary causes: Always rule out secondary causes of angle closure (neovascularization, inflammation, lens-related disorders, etc.) through careful examination 1

• Fellow eye examination: Always examine the fellow eye, as it is also at high risk for acute angle closure 2, 4

By using these diagnostic approaches, clinicians can accurately diagnose acute angle closure glaucoma and initiate prompt treatment to prevent permanent vision loss.