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

Pigment dispersion syndrome and pigmentary glaucoma: overview and racial disparities

Pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) are two stages within the same ophthalmic disease spectrum, which are known to be affected by race. The prevalence of PDS is underestimated, largely due to its minor clinical symptoms. Although the prevalence of PG is low, the visual impairment associated with PG is extremely severe. The prevalence of PDS-PG is four or more times higher in Caucasians than in Blacks or Asians, and the "classic" PDS in Caucasians has long been used as a benchmark diagnostic criterion. Following extensive research focused on African Americans and Asians, the standard for diagnosing PDS-PG was refined. At the same time, the pathogenesis of PDS is not the same in different races. Hence, the effectiveness of preventive treatment and the need for treatment may not be equivalent in different races. The rate of conversion of PDS to PG is nearly 1/3 in Caucasians and higher in blacks and Asians, requiring more aggressive treatment and monitoring. We systematically searched a PubMed database from inception to March 2022 to provide an overview of research progress in various aspects of PDS-PG. Specifically, this paper considers the effects of race on disease prevalence, clinical manifestation, diagnostic criteria, disease mechanism, hereditary traits, treatment, and prevention to provide an accurate and comprehensive guide for the diagnosis and treatment of PDS-PG in various races.

Pigmentdispersionssyndrom

Das Pigmentdispersionssyndrom ist eine Erkrankung, die durch Abschilferung von Pigment aus dem Irispigmentepithel und dessen Ablagerung im vorderen Augenabschnitt charakterisiert ist. Typisch ist eine Trias aus Ablagerungen am Hornhautendothel, zirkulären Iristransilluminationen und einer Pigmentierung des Trabekelwerks. Das Spektrum reicht vom einfachen Pigmentdispersionssyndrom bis zum Pigmentdispersionsglaukom mit Optikusatrophie.

[Pigment Dispersion Syndrome]

Pigment dispersion syndrome (PDS) is a disorder predominantly affecting young, myopic adults. It is characterised by the liberation of pigment of the iris and deposition of it on various structures of the anterior segment leading to multiple specific findings in slit lamp examination. Typical alterations are a deposition of pigment on the central corneal endothelium, circular iris transillumination defects in the mid periphery, a posterior bowing of the iris and increased pigmentation of the trabecular meshwork. Findings are usually bilateral symmetric. Posterior bowing of the iris causes rubbing of the pigmented iris epithelium against lens structures like zonular fibres with a consecutive liberation of pigment. Trabecular meshwork changes because of pigment deposition reduce aqueous outflow facility with the risk of elevated intraocular pressure and glaucoma. Pigmentary glaucoma (PG) is a secondary open angle glaucoma. Treatment of PG is similar to primary open angle glaucoma, including medical therapy, laser therapy and surgery. Peripheral laser iridotomy was shown to change iris configuration but its efficacy in the prevention of PG has not been confirmed in the literature. The purpose of this paper is to summarize information regarding ocular manifestations of PDS to facilitate an early diagnosis and to present a general view of the treatment of PG.

A case of dense pigment deposition of the posterior lens capsule

BACKGROUND

Pigment dispersion syndrome (PDS) is a well-known entity which can lead to pigmentary glaucoma (PG). This case report presents a rare presentation of PG with bilateral dense pigment deposits of the posterior lens capsule.

CASE PRESENTATION

A 72-year-old male came for his first appointment due to an asymmetric worsening of visual acuity. The examination showed unilaterally severely increased intraocular pressure, bilateral dense pigment deposition of the posterior lens capsule, and a shallow unilateral optic disk excavation. Gonioscopy revealed moderate pigmentation of the angle and a concave configuration of the peripheral iris in both eyes. The standard slit lamp examination showed no transillumination defects of either iris. Optical coherence tomography showed retinal nerve fiber layer (RNFL) thinning in the peripapillary and macular regions. An antiglaucoma medication was prescribed with a good lowering effect.

CONCLUSION

Pigment deposition of the posterior lens capsule, which has been rarely reported, is a possible important sign of PDS or PG.

[Accumulation of sulfur and phosphorus in the eye's drainage system in primary open-angle glaucoma]

PURPOSE

To analyze the chemical composition of the sclera and trabecular meshwork in patients with primary open-angle glaucoma (POAG) and to assess the impact of corneal-compensated intraocular pressure (IOP) on the chemistry of the drainage area.

MATERIAL AND METHODS

Biopsy specimens of the trabecular meshwork (89 specimens) and sclera (41 specimens) obtained from patients with POAG on maximal medical therapy were analyzed to determine the content of certain chemical elements - carbon (C), nitrogen (N), oxygen (O), aluminum (Al), calcium (Ca), chlorine (Cl), potassium (K), magnesium (Mg), sodium (Na), phosphorus (P), silicon (Si) and sulfur (S). The elements were selected based on chemical structure target tissue and sensitivity of the method used for analysis. Visualization was performed using the «EVO LS 10» (Zeiss, Germany) scanning electron microscope (SEM), and the chemical composition was studied with the «Oxford-X-MAX-50» (Oxford, UK) energy-dispersive spectrometer (EDS). Statistical analysis was performed using the Spearman correlation.

RESULTS

The IOP of patients with POAG was found to have positive correlation with the total amount of S, P, and Ca in the trabecular meshwork. The accumulation of sulfur-containing compounds associated with pigment granules in trabecular meshwork's tissue was identified. A correlation was determined between the organic and inorganic (mineral) phosphorus content in the trabeculae, and the IOP values. The organic component of phosphorus was better represented than the mineral component in patients with increased IOP.

CONCLUSION

In patients with POAG, an increase in the IOP level causes the amount of S associated with pigment granules and the proportion of organic P to increase in the trabecular meshwork, which should be taken into account in the further search for drug therapy that would potentially affect pathologically altered tissue.

Complement C3-Targeted Gene Therapy Restricts Onset and Progression of Neurodegeneration in Chronic Mouse Glaucoma

Dysregulation of the complement system is implicated in neurodegeneration, including human and animal glaucoma. Optic nerve and retinal damage in glaucoma is preceded by local complement upregulation and activation, but whether targeting this early innate immune response could have therapeutic benefit remains undefined. Because complement signals through three pathways that intersect at complement C3 activation, here we targeted this step to restore complement balance in the glaucomatous retina and to determine its contribution to degeneration onset and/or progression. To achieve this, we combined adeno-associated virus retinal gene therapy with the targeted C3 inhibitor CR2-Crry. We show that intravitreal injection of AAV2.CR2-Crry produced sustained Crry overexpression in the retina and reduced deposition of the activation product complement C3d on retinal ganglion cells and the inner retina of DBA/2J mice. This resulted in neuroprotection of retinal ganglion cell axons and somata despite continued intraocular pressure elevation, suggesting a direct restriction of neurodegeneration onset and progression and significant delay to terminal disease stages. Our study uncovers a damaging effect of complement C3 or downstream complement activation in glaucoma, and it establishes AAV2.CR2-Crry as a viable therapeutic strategy to target pathogenic C3-mediated complement activation in the glaucomatous retina.