Molecular Genetics of Pigment Dispersion Syndrome and Pigmentary Glaucoma: New Insights into Mechanisms

Figure 1

Schematic representation of PDS/PG models. In patients with PDS, pigment liberated from the posterior surface of the iris (green) circulates into the anterior chamber following the flow of aqueous humor where it deposits into the cornea and trabecular meshwork (black dots). High IOP can maintain iris bowing (red arrows) due to the reverse pupillary block in which the lens and iris act together in a ball-valve pressure system which normally acts to maintain unidirectional aqueous humor flow. There are two models of PDS/PG which differ in respect to the origin of pigment dispersion from the ciliary body to the trabecular meshwork. The structural model of PDS/PG proposes that posterior iris bowing creates inappropriate iridozonular contacts (black arrowhead, top circle) and that mechanical rubbing between the iris, zonules, and lens is responsible for liberating pigment from the IPE (asterisks, top circle). Although these structural features are well established, it still remains unclear if they predate pigment dispersion as the underlying mechanism. Animal models support IPE dysfunction as the primary driver of this dispersion. In this model, pigmented melanocytes die and/or detach from the IPE (bottom right circle) due to release of cytotoxic melanin synthesis intermediates from dysfunctional melanosomes (bumpy ovals, bottom left circle).