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Pigment Dispersion Syndrome and Pigmentary Glaucoma
Signs and Symptoms: Pigment dispersion syndrome (PDS) is generally an asymptomatic disorder discovered during routine ophthalmic evaluation. Pigmentary glaucoma (PG), a sequelae of PDS, may likewise be asymptomatic; or patients may complain of symptoms related to episodic IOP rises, such as colored haloes around lights, blurred vision or subtle ocular pain, particularly after exercise. Both conditions occur most often in young, white males between ages 20 to 40. At the slit lamp, patients with PDS and PG demonstrate bilateral liberation of iris pigment within the anterior chamber. Often, this appears as a granular brown vertical band along the corneal endothelium (Krukenberg's spindle). Pigment dusting may be evident on the lens, the iris surface and Schwalbe's line. Gonioscopy may reveal dense pigmentation resembling melted chocolate covering the trabecular meshwork for 360 degrees, most prominently in the inferior quadrant. The angle itself remains patent, and in some cases appears atypically wide open. Radial, spoke-like transillumination defects of the mid-peripheral iris are another common finding. While IOP does not alter in PDS, it may rise sharply in cases of pigmentary glaucoma, particularly after vigorous exercise or pharmacological dilation. Likewise, patients with PDS present a normal optic nerve, while those with PG manifest glaucomatous optic atrophy and field loss. Blacks--mostly middle-age to elderly females--tend to get a distinctly different form of pigmentary glaucoma. These patients typically present with no iris transillumination defects, and minimal endothelial pigment accumulation which is sometimes clinically undetectable. The amount of endothelial pigment accumulation does not predict the amount of pigment collected in the trabecular meshwork. Frequently, the patient will demonstrate pigment accumulation at the anterior lens equator. Pathophysiology: Pigment dispersion results from the proximity between the posterior iris pigment epithelium and the zonular fibers of the lens. The abrasive physical contact leads to mechanical disruption of the iris surface and release of pigment granules into the posterior chamber, which follows the flow of aqueous into the anterior chamber angle. Once lodged in the trabecular meshwork in sufficient quantity, pigment can effectively create a blockade to aqueous outflow. This results in elevated IOP with possible damage to the optic nerve--classic pigmentary glaucoma. Recent studies using ultrasound biomicroscopy have shown distinct anatomical differences in the angles of some patients with PDS and PG. In patients with PDS and PG, there is a posterior bowing of the peripheral iris that precipitates the zonular touch. The term "reverse pupillary block" describes a condition in which anterior chamber pressure intermittently exceeds that of the posterior chamber, enhancing this backward displacement of the iris and resulting in further pigment liberation and IOP spikes. The etiology is unclear, but it is thought that blinking in some patients results in this reverse valve effect. Management: Because PDS does not affect ocular health or vision, other than raising the risk for PG, you should treat patients with PDS as glaucoma suspects and monitor them for IOP spikes and optic nerve changes 3-4 times a year, with threshold visual fields and gonioscopy performed annually. Patients with pigmentary glaucoma call for topical miotics as a first line of defense. Miotics are preferable to beta-blockers or adrenergic agents because they have a dual effect; they not only lower IOP, but also contract the pupil, pulling the peripheral iris away from the zonular fibers. Pilocarpine solution 1% or 2% qid is an effective starting point; pilocarpine ointment 4% (Pilopine HS gel) once daily at bedtime may work well as an alternative in younger patients. If this regimen does not successfully control the IOP, additional agents such as beta-blockers, alpha-2 adrenergic agonists and topical carbonic anhydrase inhibitors may be necessary, either adjunctively or alternatively, to achieve the target pressure. The use of prostaglandin-like medications in managing PG is controversial. Conventional thinking dictates that these medications can increase the size of melanosomes in some patients, which could increase blockage at the trabecular meshwork and worsen the situation. However, the melanosomal enlargement occurs deep within the iris stroma and is unlikely to affect aqueous outflow. Studies show that glaucoma resulting from pigment release can be well managed by prostaglandins, and there appears to be no problems with outflow blockage from increasing melanosomes size.1 Progressive, poorly responsive cases may require argon laser trabeculoplasty or filtering procedures. More recently, clinicians have used laser peripheral iridotomy in patients with posterior iris bowing. This is an attempt to reestablish a planar configuration to the angle and to equalize the pressure between the anterior and posterior chambers. Clinical Pearls:
1. Konstas
AG, Lake S, Maltezos AC, Holmes KT, Stewart WC. Twenty-four hour intraocular
pressure reduction with latanoprost compared with pilocarpine as third-line
therapy in exfoliation glaucoma. Eye 2001 Feb;15(Pt 1):59-62. Other
reports in this section
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