Pigmentary Glaucoma

The posterior iris surface normally sits close to, but not rubbing against, the anterior lens zonules. In eyes prone to pigment dispersion — often more myopic eyes with a particular anterior segment configuration — the mid-peripheral iris bows posteriorly (reverse pupillary block), bringing the iris pigment epithelium into chronic mechanical contact with the zonules.

Pigment dispersion syndrome (PDS) is characterized by a classic triad: radial, spoke-like iris transillumination defects, a Krukenberg spindle (pigment on the corneal endothelium), and a densely, homogeneously pigmented trabecular meshwork.¹ When pigment deposition progresses to obstruct aqueous outflow and cause glaucomatous optic neuropathy, the condition is termed pigmentary glaucoma.

Posterior bowing of the mid-peripheral iris brings the iris pigment epithelium into chronic mechanical contact with the anterior lens zonules. Normal blinking and pupillary movement cause ongoing mechanical rubbing, liberating pigment granules that disperse throughout the anterior chamber and deposit on the corneal endothelium, iris surface, and — most consequentially — the trabecular meshwork, progressively increasing outflow resistance. Pupillary dilation or exercise (which increases iridozonular contact) can trigger large pigment release and acute IOP spikes.

Many patients are asymptomatic and found incidentally on slit-lamp exam. Some experience intermittent blurred vision or halos during acute pigment-liberation/IOP-spike episodes, sometimes triggered by exercise (e.g., jogging) or pupillary dilation.

Differential diagnosis includes pseudoexfoliation glaucoma (different pigment/material pattern and age group, though overlap syndrome can occur), IOL-induced secondary pigment dispersion in pseudophakic patients (a distinct mechanism — lens-iris rather than zonule-iris contact), uveitic glaucoma with pigment dispersion, and primary open-angle glaucoma without a pigmentary component.

Diagnostic evaluation does not differ fundamentally from standard glaucoma workup but must incorporate exam features specific to PDS: iris transillumination defects, Krukenberg spindle, gonioscopic pigmentation pattern, and iris configuration.¹ A proposed five-stage clinical gradation — preclinical, visible, converting to pigmentary glaucoma, established pigmentary glaucoma, and inactive PDS — helps guide the therapeutic approach at each stage.¹

Management varies by stage¹: observation for preclinical/visible PDS without glaucomatous damage; pharmacologic IOP-lowering therapy for elevated IOP or established pigmentary glaucoma; laser peripheral iridotomy, aimed at reversing the posterior iris bowing driving ongoing iridozonular contact; laser trabeculoplasty; and surgical approaches for medically uncontrolled or advanced disease.

For IOL-induced secondary pigment dispersion in pseudophakic patients, management centers on surgical correction of IOL-iris malalignment, which alone can normalize IOP if preoperative pressure was ≤24 mmHg, though additional glaucoma surgery is frequently needed when preoperative IOP is higher.³

• The classic triad — Krukenberg spindle, radial iris transillumination defects, densely pigmented trabecular meshwork — should prompt consideration of PDS in a young myopic patient
• Ask about exercise-associated visual symptoms, since pigment liberation and IOP spikes can be triggered by activities like jogging
• Laser peripheral iridotomy targets the underlying mechanism rather than just lowering IOP symptomatically
• Common pitfall: missing PDS because IOP is normal at a single visit — spikes can be missed between exams
• Common pitfall: assuming pigment dispersion findings in a pseudophakic patient represent primary PDS rather than IOL-induced secondary pigment dispersion