Pigmentary Glaucoma

Pigmentary glaucoma is secondary open angle glaucoma resulting from pigment dispersion syndrome (PDS), in which pigment is liberated from the posterior iris pigment epithelium by mechanical rubbing against lens zonules, and clogs and damages the trabecular meshwork.

• Reverse pupillary block: the iris is concave (bowed backward) due to a pressure differential, with the iris posterior surface contacting the zonules.
• Typical patient: myopic white man aged 20 to 45 years; about 10 to 50 percent of PDS patients develop pigmentary glaucoma over 15 years; men more than women (3:1 for glaucoma).
• Risk of conversion increases with high pigment load, higher pressure, male sex, and myopia. Exercise, pupillary dilation and jogging can cause pigment showers and pressure spikes.
• Associated with lattice degeneration and retinal detachment (about 6 percent).

• Often asymptomatic; may have blurred vision or haloes after exertion or dilation.
• Krukenberg spindle (vertical pigment deposition on the corneal endothelium), mid-peripheral radial iris transillumination defects ("spokes of a wheel"), dense homogeneous pigment band on the trabecular meshwork (360 degrees), pigment on the lens (Scheie stripe, on the posterior lens capsule, and the zonules), deep anterior chamber, concave iris profile.
• Pressure fluctuates widely with spikes of 40 to 60 mmHg after dilation and exercise; progressive optic neuropathy and field loss.
• Pressure can eventually decrease as the pigment shedding burns out in older age (after 50 to 60 years).

• Slit lamp for Krukenberg spindle and retroillumination for iris transillumination defects.
• Gonioscopy: wide open angle with dense, homogeneous, 360-degree posterior trabecular pigment, posterior bowing of the iris (concave) especially with accommodation or blinking.
• Ultrasound biomicroscopy or anterior segment optical coherence tomography showing iris concavity and iris zonule contact.
• Pressure measurements, optic disc evaluation, perimetry and nerve fibre layer imaging.
• Dilated peripheral retinal examination for lattice degeneration and tears.

• Pigment dispersion syndrome without glaucoma: observation, review every 6 to 12 months, and advice on avoiding vigorous exercise that causes pressure spikes; treat if pressure is raised.
• Pigmentary glaucoma: topical therapy with (prostaglandin analogue at night, timolol 0.5 percent twice daily, dorzolamide 2 percent three times daily, brimonidine 0.2 percent twice daily); pilocarpine 0.5 to 1 percent four times daily or pilocarpine gel at night reduces iris contact with zonules (but causes accommodative spasm, brow ache, myopic shift in young patients and increases retinal detachment risk).
• Selective laser trabeculoplasty with lower energy (0.4 to 0.8 mJ, 180 degrees initially) because heavily pigmented meshwork may cause pressure spikes; effect may be short lived (about 1 to 2 years).
• Laser peripheral iridotomy to reverse the iris concavity is debated; benefit is best in young patients with early disease and demonstrable concavity (the iridotomy equalises pressure between the chambers).
• Trabeculectomy with mitomycin C or drainage device for progression despite medical therapy; angle surgery (goniotomy, trabeculotomy) in young patients.
• Retinal detachment prevention: dilated examination at diagnosis, and laser demarcation of lattice or tears, with advice on warning symptoms.
• Genetic counselling is generally not needed, but examination of first degree relatives is reasonable.