Glaucoma, Pigmentary Treatment & Management

Although many individuals have pigment dispersion syndrome (PDS), fewer than one half will develop ocular hypertension or glaucoma. However, because pigment dispersion syndrome is a risk factor for the development of ocular hypertension, all patients with this disorder should undergo periodic eye examinations. This is particularly important during the pigment liberation phase of the disease. The frequency of follow-up care can be decreased when pigment liberation ceases or trabecular pigmentation begins to diminish.

• Pigment dispersion syndrome is typically a bilateral disease, although asymmetry may occur. A correlation is noted between the amount of pigment lost from the posterior surface of the iris, increased degree of pigmentation in the trabecular meshwork, and degree of dysfunction in the trabecular meshwork as evidenced by elevation of the intraocular pressure (IOP). The size and density of the Krukenberg spindle does not necessarily correlate with trabecular meshwork damage. However, the amount of pigment that is presented to the trabecular meshwork does play a role in the elevation of the IOP. Markedly asymmetric disease is usually due to an additional factor, making one eye worse, such as anisometropia or the development of exfoliation syndrome or angle recession, or an additional factor acting to prevent the development of pigment dispersion syndrome, such as aphakia or Horner syndrome.
• Progressive glaucomatous optic neuropathy in pigmentary glaucoma (PG) is primarily pressure dependent and reduction of IOP is the mainstay of therapy. In addition to monitoring of IOP, sequential ophthalmic examinations should include gonioscopy to assess the degree and progression of trabecular pigmentation, stereoscopic evaluation and photography of the optic nerve, and perimetry.
• Because the degree and stage of pigment liberation, IOP, and extent of glaucomatous optic neuropathy vary among individuals, each must be evaluated to determine the proper course of intervention. As understanding of the pathogenesis of pigment liberation expands, consideration also should be given to gearing therapy toward eliminating acute pigment release, rather than just treating elevated IOP.
• The mainstay of initial medical therapy for pigmentary glaucoma continues to be aqueous suppression with a topic beta-blocker, primarily because of the relatively easy dosing schedule and minimal side effects.
• Parasympathomimetics may also be administered.

  • In theory, therapy directed at increasing relative pupillary block should relieve iridozonular contact and diminish pigment liberation. The relief of iridozonular contact following miotic therapy has been demonstrated with ultrasound biomicroscopy (UBM). Pupillary miosis increases resistance to aqueous flow from the posterior chamber, past the lens surface, and through the pupil into the anterior chamber. This increased resistance allows aqueous pressure to build within the posterior chamber (ie, relative pupillary block), and forces the iris to move anteriorly, away from the zonules, and assume a convex configuration. However, strong miotics in young individuals rarely are tolerated because of the associated spasm of accommodation and blurring of vision.
  • Low-dose pilocarpine, in the form of Ocusert, often provides enough miosis to create pupillary block, without disabling adverse effects. A careful peripheral retinal examination should be performed before and after the institution of or change in miotic therapy because of the higher incidence of retinal breaks and detachment in these patients.
• Alpha-agonists are useful in pigmentary glaucoma, but the development of allergy in as many as 50% of patients precludes the long-term use of dipivefrin, epinephrine, and apraclonidine in many individuals. Brimonidine tartrate 0.2% may provide satisfactory IOP with less allergic reaction than other drugs in this class.
• Topical carbonic anhydrase inhibitors are useful agents for treating pigmentary glaucoma and are generally well tolerated. Systemic agents should be reserved for particularly difficult circumstances or when the risks of surgery are unacceptably high.
• Prostaglandin analogues, which lower IOP by increasing uveoscleral outflow are effective in treating pigmentary glaucoma and offer the advantage of once daily administration. The iris surface color change that may occur during therapy appears to involve increased melanin production by iris melanocytes and is not known to affect the iris pigment epithelium (IPE) or result in pigment dispersion.

• Laser trabeculoplasty: Argon laser trabeculoplasty may be offered as a treatment in the management of uncontrolled pigmentary glaucoma. Although the initial result is often good, a larger proportion of patients can lose control of IOP when compared to patients with primary open-angle glaucoma (POAG), and the loss of control can occur in less time. In contrast to other forms of open-angle glaucoma, younger patients appear to respond better to trabeculoplasty than older individuals. Selective laser trabeculoplasty has been reported to result in marked and sustained IOP elevation, necessitating trabeculectomy in a few eyes with pigmentary glaucoma; therefore, it should be used with great caution.^[10]
• Laser iridectomy: Laser iridectomy eliminates the iris concavity present in most patients with pigment dispersion syndrome by permitting equalization of pressures between the anterior and posterior chambers. This causes the iris to become flat, thereby decreasing iridozonular contact and reversing the underlying anatomical defect, which results in pigment dispersion. Anecdotal evidence suggests that this can prevent continued pigment liberation, result in a reversal of trabecular pigmentation, and, subsequently, lower IOP. However, long-term lowering of IOP and stabilization of glaucomatous optic neuropathy and visual field loss have not been demonstrated conclusively. Although theoretically sound, laser iridectomy should be used with caution because of the paucity of data regarding the long-term efficacy of this procedure.
• Filtering surgery: The surgical management of patients with pigmentary glaucoma follows the same principles and considerations used in the management of primary open-angle glaucoma. The appearance and change in the optic nerve along with visual field defects should be the principal guidelines used in deciding whether surgery is needed. Most patients respond well to standard filtration operations, although antifibrosis agents may be indicated to achieve a low target pressure or for reoperation. No unusual problems are typically encountered during cataract surgery.