Pigment dispersion syndrome


Pigment dispersion syndrome

Description, Causes and Risk Factors:

Increased resistance to flow of aqueous humor through the pupil from the anterior chamber to the posterior chamber, leading to posterior bowing of the peripheral iris against the zonules; a possible mechanism for pigmentary glaucoma.

Pigmentary dispersion syndrome (PDS) is a condition in which increased amounts of pigment circulate within the front portion of the eye. This often results in having pigment layered on the back of the cornea, thinning of the iris, and clogging of the ocular drainage system with pigment. This pigment can block the drainage channel enough to cause an increase in intraocular pressure (IOP).

PDS is caused by excess pigment floating around in the eye that has been released from the back side of the iris. Some people have a unique eye anatomy that causes the lens zonules to rub abrasively onto the back of the iris. Lens zonules are thin fibers that hold the crystalline lens of the eye in place right behind the iris. As the iris and lens changes shape, the zonules chafe against the iris and the pigment begins to flake off.

While anyone can develop PDS, it seems to be much more common in younger, white males between the ages of 20-40. Interestingly, most people who develop PDS are nearsighted (myopic).

Blacks -- mostly middle-aged-to-elderly females tend to get a distinctly different form of PDS. 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.

Symptoms:

PDS is characterized by the presence of Krukenberg's spindles, iris transillumination defects, trabecular meshwork (TM) pigmentation and backward bowing of the iris.Symptoms of PDS are most likely caused by sudden increases in eye pressure. The condition can cause episodes of symptoms, including the following:

    Blurred vision.

  • Colored halos around lights.

  • Mild ocular pain.

Diagnosis:

Because the pigment floats around, it gets deposited onto the back surface of the cornea in a vertical pattern. In eye care, this pigmentary deposition is known as "Krukenberg's spindle." Because this pigment comes off the back of the iris, the doctor can also see "transillumination of the iris." That means the doctor sees slit-like defects in the iris where light passes through because of the lack of pigment. By using Gonioscopy, he/she can observe excess pigment that is deposited in the drainage canal of the eye. Eye pressure may or may not be elevated. If the patient has developed pigmentary glaucoma, then signs of glaucoma can also be seen.

Treatment:

Because PDS does not affect ocular health or vision, other than raising the risk for pigmentary glaucoma (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 every 6 months. Patients with PG 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% four times a day is an effective starting point; pilocarpine ointment 4% (Diocarpine™) 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.

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.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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