Gonioscopic Pathologic Findings

Angle Neovascularization

Angle neovascularization (NVA) is fine, abnormal new blood vessel growth crossing the ciliary body band and angle structures: the angle counterpart of iris neovascularization (NVI, rubeosis). Both arise from VEGF released by ischemic retina, most classically in proliferative diabetic retinopathy, though central retinal vein occlusion and ocular ischemic syndrome produce the same picture. Left untreated, the fibrovascular membrane driving NVA contracts over time and drags the iris root into permanent contact with the trabecular meshwork, producing synechial angle closure. That progression to neovascular glaucoma is one of the hardest glaucoma subtypes to manage, and it is why early NVA on gonioscopy, before synechiae have formed, is worth looking for.

Peripheral Anterior Synechiae

Peripheral anterior synechiae (PAS) are broad, irregular adhesions of iris tissue to the trabecular meshwork or cornea. They obliterate the angle recess and do not resolve with indentation gonioscopy. That non-resolution is what separates true PAS from normal iris processes: fine, lacy strands of iris tissue that cross the ciliary body band without occluding the angle and are themselves a normal anatomic variant. PAS forms as the end stage of several different pathologic processes (chronic appositional angle closure, NVA, inflammation), so finding it on gonioscopy is a prompt to search for the underlying cause, not a diagnosis on its own.

When PAS turns up in a narrow, occludable angle, it also marks a specific point on a staging scale. Primary angle-closure suspect (PACS) is an occludable angle, iridotrabecular contact over 180 degrees or more on indentation, with normal IOP and no PAS. Primary angle closure (PAC) is the same occludable angle once something has gone wrong: PAS, elevated IOP, or patchy trabecular pigment clumping, but still no glaucomatous optic nerve or visual field damage. Add that optic nerve and field damage and the diagnosis becomes primary angle-closure glaucoma (PACG). The distinction changes management: PACS is usually observed or treated prophylactically with a peripheral iridotomy, while PAC and PACG both need active IOP-lowering treatment and ongoing glaucoma follow-up.

Sampaolesi Line and Pseudoexfoliation

The Sampaolesi line is a wavy, irregular band of pigment deposited anterior to, and sometimes directly on, Schwalbe's line. It forms when pigment liberated off a heavily pigmented trabecular meshwork overflows anteriorly, and it is seen characteristically in both pseudoexfoliation syndrome and pigment dispersion syndrome. In pseudoexfoliation, dense, scalloped trabecular pigmentation, typically most prominent inferiorly, together with a Sampaolesi line is virtually pathognomonic. That is especially true when visible pseudoexfoliative material on the iris and lens capsule, seen outside the gonioscopic view, backs it up.

Angle Recession

Angle recession is a traumatic finding. Blunt ocular trauma can tear the ciliary body between its longitudinal and circular muscle fibers, producing a focally widened ciliary body band on gonioscopy, often with torn iris processes nearby. It can present months to years after the inciting trauma as a delayed secondary glaucoma, so unexplained unilateral elevated IOP with a history of blunt trauma should prompt a careful gonioscopic search for recession. A cyclodialysis cleft is a distinct entity: it shows a direct separation of the ciliary body from the scleral spur, with a visible gap communicating to the suprachoroidal space. Because aqueous escapes through that gap rather than accumulating, a cleft tends to lower IOP rather than raise it.

A third pressure-related finding, distinct from either traumatic entity above, is blood visible inside Schlemm's canal itself. The canal is normally invisible on gonioscopy. It fills with blood when episcleral venous pressure exceeds the pressure inside it, most often from ocular hypotony or from something obstructing episcleral venous outflow, such as a carotid-cavernous fistula, an orbital varix, or Sturge-Weber syndrome. In a child or teenager with a facial port-wine stain, blood in Schlemm's canal on an otherwise open angle points toward Sturge-Weber-related glaucoma, which raises IOP through impaired venous drainage rather than through synechial closure or pupillary block.

Plateau Iris Syndrome

Plateau iris syndrome looks deceptively similar to ordinary pupillary block at first glance, but the anatomic cause is completely different: an anteriorly positioned (anteriorly rotated) ciliary body physically holds the peripheral iris up against the trabecular meshwork, independent of pupillary block. A laser peripheral iridotomy (LPI) only relieves pupillary block, so it may open the central angle in plateau iris while the peripheral angle stays narrow. On ultrasound biomicroscopy (UBM) this produces the classic "double hump" sign, where the ciliary body and peripheral iris create two separate anterior bulges. Since LPI alone does not correct the underlying anatomy, management typically adds peripheral laser iridoplasty (gonioplasty), which flattens the peripheral iris directly.

Provocative Testing and Advanced Imaging

When angle status is borderline, or before gonioscopy or imaging can be performed, dark-room prone provocative testing can help identify eyes at risk for angle closure. The patient lies prone in a dark room for one hour; a rise in IOP of 8 mmHg or more is generally considered a positive result. Darkness maximizes pupillary block by dilating the pupil, and the prone position adds gravity, pooling aqueous anteriorly. Sensitivity and specificity are imperfect compared with direct gonioscopic assessment.

Ultrasound biomicroscopy (UBM) and anterior segment OCT (AS-OCT) are non-contact imaging alternatives that give a cross-sectional view of the angle. UBM uses high-frequency 35–50 MHz ultrasound, compared with 10 MHz for conventional B-scan, achieving roughly 50 µm axial resolution. That resolution is high enough to image the ciliary body, pars plana, supraciliary space, and posterior iris surface, structures not visible on AS-OCT. UBM is therefore the imaging modality of choice for plateau iris configuration, ciliary body cysts, and supraciliary effusions causing secondary angle closure.

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