How can I differentiate between primary open-angle glaucoma and other types of glaucoma in a primary care setting?

In a primary care setting, differentiating primary open-angle glaucoma (POAG) from other types of glaucoma primarily involves assessing the anterior chamber angle and intraocular pressure (IOP), alongside optic nerve and visual field evaluation.

Key differentiating steps include:

• Performing gonioscopy or, if unavailable, the van Herick test or anterior segment OCT to assess the peripheral anterior chamber angle configuration and depth. POAG typically presents with an open anterior chamber angle, whereas angle-closure glaucomas show narrow or closed angles ¹.
• Measuring IOP using Goldmann-type applanation tonometry, as non-contact tonometry alone is insufficient for referral decisions ¹. Elevated IOP (≥24 mmHg) supports suspicion of glaucoma but is not diagnostic alone ¹.
• Conducting optic nerve head assessment via stereoscopic slit lamp biomicroscopy and, if available, optical coherence tomography (OCT) to detect optic nerve damage characteristic of glaucoma ¹.
• Performing central visual field assessment using standard automated perimetry to identify visual field defects consistent with glaucoma ¹.

In contrast, angle-closure glaucoma often presents acutely with symptoms such as eye pain, redness, and visual disturbance, and requires urgent referral and treatment ². Uveitic glaucoma and other secondary glaucomas may present with signs of inflammation or other ocular pathology, which are not features of POAG and require slit-lamp examination and specialist assessment ³.

Therefore, in primary care, the main practical differentiation is through anterior chamber angle assessment (open in POAG, narrow or closed in angle-closure glaucoma) combined with IOP measurement and optic nerve/visual field evaluation to guide referral ¹,²,³.