Pigment Dispersion Syndrome
In pigment dispersion syndrome, the zonular fibers rub the posterior iris pigment epithelium, resulting in the release of pigment granules throughout the anterior segment. Posterior bowing of the iris caused by the so-called “reverse pupillary block” configuration is present in many eyes with pigment dispersion syndrome. This concave iris configuration results in greater contact with the zonular fibers, causing increased release of pigment granules.
Pigment dispersion syndrome classically presents with pigment deposits on the corneal endothelium, trabecular meshwork, and lens periphery, as well as with midperipheral iris transillumination defects in a spokelike pattern. The pigment is typically deposited on the corneal endothelium in a vertical spindle pattern, referred to as a Krukenberg spindle (Fig 4-8); the pattern of corneal pigment deposition is the result of aqueous convection currents and subsequent phagocytosis of pigment by the corneal endothelium. The presence of a Krukenberg spindle is not necessary for a diagnosis of pigment dispersion syndrome. Moreover, this sign may be present in other diseases, such as pseudoexfoliation syndrome. The midperipheral iris transillumination defects are a result of contact between the zonular fibers and the posterior iris pigment epithelium (Fig 5-8). On gonioscopy, the trabecular meshwork commonly appears as homogeneous and densely pigmented, with speckled pigment at or anterior to the Schwalbe line (Fig 6-8), often forming a Sampaolesi line. When the eye is dilated, pigment deposits may be seen on the zonular fibers, on the anterior hyaloid, and in the equatorial region of the lens capsule (Zentmayer line/ring or Scheie stripe; Fig 7-8).
Figure 8-4 Krukenberg spindle in a patient with pigmentary glaucoma.
(Reproduced from Alward WLM, Longmuir RA. Color Atlas of Gonioscopy. 2nd ed. American Academy of Ophthalmology; 2008:75. Fig 9-1.)
Figure 8-5 photograph of the classic spokelike iris transillumination defects of pigment dispersion syndrome.
(Courtesy of Angelo P. Tanna, MD.)
Figure 8-6 Characteristic heavy, uniform pigmentation of the trabecular meshwork (arrows) occurring in pigment dispersion syndrome and pigmentary glaucoma.
(Courtesy of M. Roy Wilson, MD.)
Figure 8-7 In pigment dispersion syndrome, pigment deposits are visible in the equatorial region of the lens capsule (Zentmayer ring or Scheie stripe) and on the zonular fibers.
(Courtesy of Angelo P. Tanna, MD.)
With increasing age, the signs of pigment dispersion may decrease as a result of normal growth of the lens, inducing a physiologic pupillary block and anterior movement of the iris. Loss of accommodation may also occur. As pigment dispersion is reduced, the deposited pigment may fade from the corneal endothelium, trabecular meshwork, or anterior surface of the iris.
Approximately 15% of cases of pigment dispersion syndrome progress to glaucoma or elevated IOP that requires treatment. Pigmentary glaucoma is 3 times more common in men than in women, particularly men who are young or middle-aged (20–50 years) and myopic. The presumed mechanism of elevated IOP is obstruction of the trabecular meshwork by pigment granules. Pigmentary glaucoma is characterized by wide fluctuations in IOP, which can exceed 50 mm Hg in untreated eyes. Affected patients may have extreme elevations in IOP following exercise or pupillary dilation because of an excessive liberation of pigment. Symptoms associated with such elevated IOPs may include halos, intermittent blurry vision, and ocular pain.
Medical treatment is often successful in reducing elevated IOP. Most patients respond reasonably well to laser trabeculoplasty, although its effect may be short-lived. Studies have shown paradoxical elevations of IOP after laser trabeculoplasty in eyes with heavy trabecular meshwork pigmentation including pigmentary glaucoma; thus, it may be advisable to use lower laser energy in this condition. Filtering surgery is usually successful; however, extra care is warranted in young myopic male patients, who are at increased risk for hypotony maculopathy. Laser peripheral iridotomy has been proposed as a means of minimizing posterior bowing of the iris by alleviating the pressure differential between the anterior chamber and the posterior chamber (Fig 8-8). However, multiple studies, including randomized trials, have failed to show a benefit of laser iridotomy for treatment of this condition.
Niyadurupola N, Broadway DC. Pigment dispersion syndrome and pigmentary glaucoma—a major review. Clin Exp Ophthalmol. 2008;36(9):868–882.
Reistad CE, Shields MB, Campbell DG, et al; American Glaucoma Society Pigmentary Glaucoma Iridotomy Study Group. The influence of peripheral iridotomy on the intraocular pressure course in patients with pigmentary glaucoma. J Glaucoma. 2005;14(4):255–259.
Siddiqui Y, Ten Hulzen RD, Cameron JD, Hodge DO, Johnson DH. What is the risk of developing pigmentary glaucoma from pigment dispersion syndrome? Am J Ophthalmol. 2003;135(6):794–799.
Figure 8-8 Pigment dispersion syndrome. A, Ultrasound biomicroscopy image of concave iris configuration in pigmentary glaucoma, before laser peripheral iridotomy (LPI). B, Same eye, after LPI, with resolution of the posterior bowing of the iris.
(Courtesy of Charles J. Pavlin, MD.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.