Pigment Dispersion Glaucoma

Glaucoma is an ocular disease characterized by ocular hypertension that leads to optic neuropathy and visual field loss. Aqueous humor is secreted in the posterior chamber (PC) by the ciliary body, then moves into the anterior chamber (AC) through the pupil. The aqueous is then drained from the trabecular meshwork (TM) located at the angle between the cornea and iris. Glaucoma due to blockage of aqueous outflow from the TM by the iris or angle is defined as closed-angle glaucoma. When gonioscopy shows no evidence of angle closure, the optic neuropathy related to elevated intraocular pressure (IOP) is defined as open-angle glaucoma. Pigment dispersion glaucoma or pigmentary glaucoma (PG) is considered secondary open-angle glaucoma. PG and pigment dispersion syndrome (PDS) have similar clinical characteristics, representing a disease spectrum. PDS can convert into PG when there is the presence of elevated intraocular pressure (IOP) with visual field defects and glaucomatous optic neuropathy. Friedrich E. Krukenberg described Krukenberg spindle in 1899. An interesting triad of symptoms for PG was first reported by Sugar et al. in 1949, defined by corneal endothelial pigment depositions on the posterior side of the cornea, mid-peripheral radial iris transillumination defects, and heavy pigmentation in the TM. Campbell reported that pigment dispersion and accumulation in PG could be caused by pigment loss (melanin granules) from constant friction and rubbing between the posterior iris pigment epithelium and the lens zonules during physiological pupil movement, which may be facilitated by the posterior bowing of the iris and reverse pupillary block that tends to be more prevalent in myopic eyes with a large iris. The pigment deposited in the AC contributes to chronic damage and death of TM cells over time, limiting the proper function and efficiency. Elevated IOP in PG results from aqueous buildup and reduction of TM aqueous humor outflow, leading to visual field loss associated with chronic optic neuropathy. The disease, which is typically bilateral, is prevalent in males with myopia and is typically diagnosed between 30 to 50 years.