with ALAN G. KABAT, O.D.

An 81-year-old black female presented complaining of blurred vision at both distance and near in her left eye. She reported no significant ocular history. Her medical history was positive for hypertension, which she controlled with Norvasc (amlodipine besylate) and hydrochlorothiazide. She reported no known drug allergies, and her family ocular and medical history was unremarkable.

Diagnostic Data

Best-corrected visual acuity was 20/40 O.D., 20/70 O.S. Confrontation visual fields were full in the right eye, but revealed an inferior nasal defect in the left. Ocular motility was unrestricted. Pupils were equal, round and reactive to light, with no afferent defect.
 
Slit lamp biomicroscopy revealed barely observable pigment on the corneal endothelium and a few pigment cells within the anterior chamber O.U. Iris transillumination demonstrated no notable slit defects in the mid-periphery or at the pupillary margin in either eye. Grade 2+ nuclear sclerosis was evident O.U. Applanation tensions were 38mm Hg O.U. Gonioscopy revealed visible ciliary body O.U., with dense pigmentation covering the trabecular meshwork for 360°.

Dilation revealed pronounced spoke-like pigment deposition on the peripheral anterior lens capsule O.U. Fundus examination revealed cup-to-disc ratios of 0.80/0.80 O.D. and 0.95/0.95 O.S. The peripheral retina appeared intact 360° O.U. Subsequent threshold visual field testing demonstrated constriction of the central 30° O.U., more notable and severe O.S.

Diagnosis and Treatment

This patient has atypical pigment dispersion syndrome and pigmentary glaucoma O.U. Her condition is more advanced in the left eye.
 
We prescribed Alphagan (brimonidine) O.U. bid and had the patient return in one week for re-evaluation. At that visit, IOP measured 17mm Hg O.D., 22mm Hg O.S. Visual fields appeared consistent with the initial evaluation. However, at subsequent follow-up three weeks later, IOP returned to near pretreatment levels in both eyes. We increased the Alphagan to tid and added Azopt (brinzolamide), but this had little effect.

Given the patient’s advanced disease state and poor response to medical therapy, we referred her to an ophthalmic surgeon for trabeculectomy.

Discussion

Although pigmentary glaucoma was first described as a rare clinical entity, today it is recognized as a leading cause of secondary open-angle glaucoma. The development of pigmentary glaucoma is the main sequela of pigment dispersion syndrome (PDS). Reports indicate that PDS progresses to pigmentary glaucoma in 10-50% of patients.1,2
Possible risk factors for the progression of PDS into pigmentary glaucoma include:
  • Male gender.
  • Severe myopic refractive error.
  • Presence of a Krukenberg’s spindle.1
A diagnosis of pigmentary glaucoma may be made when any of these accompanies PDS: elevated IOP, glaucomatous nerve cupping and/or glaucomatous visual field defects. Patients who present with pigmentary glaucoma may be asymptomatic, or they may complain of blurred vision, subtle ocular pain or haloes around lights. Males have a higher incidence of developing pigmentary glaucoma than females, and this condition usually develops at a younger age in men than it does in women.1,e The average age of diagnosis is in the third to fifth decade of life.1,2
 
The pathophysiologic mechanism behind pigmentary glaucoma may not be a simple cause and effect. One would assume that pigment accumulates in the trabecular meshwork (TM) and then impedes aqueous outflow, making IOP rise. However, many individuals with significant pigment dispersion do not manifest ocular hypertension. Other factors such as congenital, hereditary and hormonal variations likely play a role in the development of pigmentary glaucoma.

While reports of pigmentary glaucoma are most common in whites and rare in blacks, this condition may actually be more common in blacks than previously recognized. One report suggests that the prevalence of PDS in blacks may be as high as 15 cases per 10,000 patients past age 7.4 In comparison, the prevalence of PDS in the general population is about 245 cases per 10,000.5

One might similarly conclude that pigmentary glaucoma is also more prevalent than expected in blacks. But it is probably improperly diagnosed as primary open-angle glaucoma for several reasons. Many practitioners may be apt to dismiss excessive pigment within the trabecular meshwork as “normal” when examining black patients. Also, many of the recognized clinical signs of pigmentary glaucoma may be absent in this population. These “classic” signs that have been identified in predominately white populations include:

  • Mid-peripheral iris transillumination defects.
  • Anterior iris stromal pigment dusting.
  • Posterior iris bowing.
  • Krukenberg’s spindle.
  • Dense pigmentation of the trabecular meshwork.
  • Pigment deposition on intraocular structures such as the iris, lens capsule and lens zonules.
Similarly, black patients with PDS and pigmentary glaucoma typically exhibit dense pigmentation of the TM, but may also show significant lenticular pigment deposition, and corneal endothelial pigmentation in varying degrees.1,4,6-7
 
There is some controversy regarding endothelial pigment in these patients, however. Some reports indicate dense pigment deposition in the form of Krukenberg’s spindle,6 while others indicate only sparse or wholly absent endothelial pigment.4

Also rare among black patients with pigmentary glaucoma are iris transillumination defects. Studies have shown that the frequency of iris transillumination defects, as detected with infrared analysis and standard slit lamp examination, is significantly lower among black patients vs. non-blacks.8

Because the clinical presentation varies so widely within the black population and there is no well-established diagnostic criteria, the diagnosis of pigmentary glaucoma in the black population is more challenging and most likely underdiagnosed.

In 1990 researchers described a specific, new form of PDS that affects black hyperopic females, typically between the ages of 60 and 80 years.6 This group exhibited dense TM pigmentation and Krukenberg’s spindle. The researchers reasoned this age-related PDS variant results from a different mechanism than the classical variety.

In the classic presentation, the release of pigment occurs secondary to the mechanical contact between the posterior iris surface and the lens zonules. In the age-related variant, pigment releases due to the mechanical rubbing of the maturing lens on the posterior iris surface.6 The released pigment follows the flow of aqueous and ultimately accumulates in the TM.

The management of pigmentary glaucoma may involve topical IOP-lowering agents, argon laser trabeculoplasty (ALT) or filtering surgery. Miotics (1-2% pilocarpine) reduce IOP by facilitating trabecular outflow. They also help decrease the mechanical contact between the posterior iris and the lens zonules, which lowers the amount of pigment release.

Although this would make miotics seem a preferable treatment option, their short duration of action and significant side effects (burning, accommodative spasm, brow-ache, pupillary miosis) make them an unpopular choice among most doctors today. Adrenergic agonists (e.g., brimonidine/Alphagan), beta-blockers (e.g., timolol) and carbonic anhydrase inhibitors (e.g., brinzolamide/Azopt) all lower IOP by decreasing aqueous production. Any of these are good therapeutic options for patients with pigmentary glaucoma, unless other contraindications exist.

Prostaglandin analogs such as Xalatan (latanoprost) and Travatan (travoprost) may also effectively treat this disorder. These drugs enhance uveoscleral outflow of aqueous, thereby decreasing IOP. Despite the possible increase in stromal iris melanocytes associated with this category of drugs, there is no conclusive evidence that their use increases the severity of pigment dispersion.

When medical management is no longer sufficient to control progressive pigmentary glaucoma, then surgical intervention is necessary. ALT and filtering surgeries can reduce IOP and minimize glaucomatous field loss. Because black patients usually manifest a more recalcitrant and severe form of pigmentary glaucoma, surgery often becomes necessary for this population earlier in the course of the disease.

Pigmentary glaucoma is traditionally considered a secondary glaucoma that is found almost exclusively in the white population. But more recent studies indicate that this condition may have a much higher prevalence in the black population than previously thought. So, when you suspect open-angle glaucoma in a black patient, make sure to include pigmentary glaucoma in the differential diagnosis. The management of this condition often warrants a different protocol than other types of glaucoma.

Dr. Ng is completing a residency in primary eye care at Nova Southeastern University in Fort Lauderdale, Fla. Dr. Kabat is an associate professor at Nova Southeastern and a co-author of Review of Optometry’s Handbook of Ocular Disease Management.

  1. Farrar SM, Shields MB, Miller KN, Stoup CM. Risk factors for the development and severity of glaucoma in the pigment dispersion syndrome. Am J Ophthalmol 1989;108:223-9.
  2. Richter CU, et al. Pigmentary dispersion syndrome and pigmentary glaucoma. A prospective study of the natural history. Arch Ophthalmol 1986;104:211-5.
  3. Farrar SM, Shields MB. Current concepts in pigmentary glaucoma. Surv Ophthalmol 1993;37:233-52.
  4. Roberts DK, Chaglasian MA, Meetz RE. Clinical signs of the pigment dispersion syndrome in blacks. Optom Vis Sci 1997;74:993-1006.
  5. Ritch R, Steinberger D, Liebmann JM. Prevalence of pigment dispersion syndrome in a population undergoing glaucoma screening. Am J Ophthalmol 1993; 115:707-10.
  6. Semple HC, Ball SF. Pigmentary glaucoma in the black population. Am J Ophthalmol 1990;109:518-22.
  7. Roberts DK, Miller E, Kim LS. Pigmentation of the posterior lens capsule central to Wieger’s ligament and the Scheie line: a possible indication of the pigment dispersion syndrome. Optom Vis Sci 1995;72:756-62.
  8. Roberts DK, Chaglasian MA, Meetz RE. Iris transillumination defects in pigment dispersion syndrome as detected with infrared videography: comparison between a group of blacks and a group of nonblacks. Optom Vis Sci 1999;76:544-9.