Gonioscopy in Eye Care

Gonioscopy is the only routine clinical method to directly view the anterior chamber angle, making it indispensable for diagnosing and staging glaucoma. Identifying whether the angle is open, narrow, or closed determines laser, surgical, and medical decisions that protect optic nerve health. Subtle findings such as peripheral anterior synechiae, neovascularization, or excessive pigment can shift a case from routine to urgent. Regular angle evaluation also verifies whether elevated pressure truly represents open angle disease or an angle related mechanism.

Choose a three mirror lens when you want a detailed view of the angle and peripheral retina, noting it requires coupling gel and more chair time. A four mirror lens allows rapid, indentation capable surveying without gel and is ideal for routine screening and dynamic assessment of appositional closure. After instilling topical anesthetic, place the lens gently on the cornea, stabilize your hands, and sweep illumination and focus through each quadrant systematically. Keep the slit beam narrow and offset to avoid causing pupil constriction that can falsely open a borderline angle.

Identify Schwalbe line, non pigmented and pigmented trabecular meshwork, scleral spur, and ciliary body band from anterior to posterior. Being able to see the scleral spur generally means the angle is at least moderately open, while visibility of the ciliary body band indicates a very open configuration. The Shaffer system grades angle width by estimating degrees (0 to 4), while Spaeth adds iris insertion, configuration, and pigmentation for a richer description. Record both the most open and narrowest quadrant so future comparisons are meaningful.

Use gonioscopy to detect appositional or synechial closure in primary angle closure suspects and to decide when laser iridotomy is appropriate. In open angle glaucoma or ocular hypertension, inspect the trabecular meshwork for pigment dispersion, pseudoexfoliative material, or blood that may alter outflow. Look for fine neovascular fronds in suspected ischemic disease and for angle recession after blunt trauma. Routine screening of hyperopes, older adults, and those with a family history of angle closure prevents missed narrow angles that can decompensate suddenly.

Excessive pressure on the cornea can artificially widen the angle, while insufficient coupling with a three mirror lens can blur landmarks. Bright light and small pupil size may open a borderline angle, so dim illumination and a narrow beam help reveal true status. Indentation with a four mirror lens distinguishes appositional closure, which opens with pressure, from synechial closure, which does not. Always disinfect lenses properly, document any corneal epithelial disruption, and avoid gonioscopy if there is a large epithelial defect or active infection.

Chart the grade for each quadrant, the grading system used, presence of pigment, blood, synechiae, or neovascularization, and whether indentation was performed. Explain findings to patients in simple terms, such as “your drain is partially blocked,” to improve adherence to recommended laser or drop therapy. Schedule periodic rechecks for narrow angles, post laser evaluations, or when pressure control changes. Consistent terminology and templated fields in your EMR improve clarity across providers and support evidence based decisions at future visits.