Case of Pigment Dispersion Syndrome with Iris transillumination defects

Dr Lance Lyons, and Dr Alec Amram at University of Texas Medical Branch, Galveston, TX have reported a rare case of Pigment Dispersion Syndrome with Iris transillumination defects. The case has appeared in the New England Journal of Medicine.

Pigment dispersion syndrome (PDS) happens when the pigment that gives iris its colour rubs off the back of iris. The pigment may float around to other parts of the eye and tiny bits of it may clog eye's drainage angle giving rise to eye pressure problems including glaucoma. Up to 50 per cent of people with this condition can develop elevated eye pressure and glaucoma if the pigment decreases the outflow of fluid. This condition is more common in people that are nearsighted. Although rare, pigment dispersion syndrome and pigmentary glaucoma tend to occur at a younger age than primary open-angle glaucoma.

A 44-year-old man with a family history of glaucoma presented to the ophthalmology clinic to reestablish care after relocating. He had previously started using timolol, brimonidine, and brinzolamide, which had been prescribed because of increased intraocular pressure. The measured pressure was 21 mm Hg (normal range, 12 to 20) in each eye, and his visual acuity was 20/25 in each eye.

Examination revealed circumferential spoke-like iris transillumination defects in both eyes. Gonioscopy of the anterior chamber revealed an open, yet heavily pigmented, iridocorneal angle and a cup-to-disk ratio of 0.4 in the right eye and 0.6 in the left eye. A diagnosis of pigment dispersion syndrome was made. Posterior bowing of the iris causes chafing of zonular fibres of the lens and release of pigment. This pigment accumulates in the trabecular meshwork of the eye and may prevent aqueous humour drainage, thereby leading to increases in intraocular pressure and subsequent optic nerve damage known as pigmentary glaucoma. The patient underwent selective laser trabeculoplasty but continued to use pressure-lowering eye drops to control his intraocular pressure.

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DOI: 10.1056/NEJMicm1903842