Pigmentary Glaucoma
Chat Highlights
August 13, 2003

Norma Devine, Editor

On Wednesday, August 13, 2003, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Pigmentary Glaucoma."

Moderator:  Good evening, Dr. Wilson.  Tonight we will be discussing pigmentary glaucoma.  First, what is pigmentary glaucoma?

Dr. Rick Wilson:  Pigmentary glaucoma is a secondary glaucoma caused by an accumulation of pigment in the trabecular meshwork of the eye, blocking the outflow of fluid.

P:  Why does pigmentary glaucoma respond better to argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT) than other types of glaucoma, except pseudoexfoliation (PXF)?   

Dr. Rick Wilson:  It responds better because the pigment in the trabecular meshwork absorbs the laser light so well, and the pigment can be removed from the trabecular meshwork by the rejuvenated cells, at least enough to increase the outflow.

P:  Is the prognosis good for pigmentary glaucoma?

Dr. Rick Wilson:  The prognosis seems to be about the same as for chronic open-angle glaucoma but, on average, the onset is much earlier than primary open-angle glaucoma (POAG).  

P:  Is pigmentary glaucoma rare?  Is it found in one race more than another, in males more than females, and is age a factor?  

Dr. Rick Wilson:  The syndrome is usually seen in patients with large, near- sighted eyes.  In such eyes, the ligaments that hold the lens in place rub on the back of the iris, knocking particles of brown pigment into the fluid in the eye.  The fluid carries the pigment to the trabecular meshwork, where the particles are sieved out, like leaves in a storm drain.  Pigmentary glaucoma is not rare, is found more often in males than in females, and usually the patients are in their late 20's to early 40's.

P:  What is the difference between pigment-dispersion syndrome (PDS) and pigmentary glaucoma?

Dr. Rick Wilson:  There is a syndrome of PDS where the pigment gets knocked off the iris and blocks the drain, but not to the extent that the IOP (intraocular pressure) is elevated and glaucoma ensues.

P:  How is pigmentary glaucoma diagnosed? How can a doctor see it?

Dr. Rick Wilson:  A doctor can use a gonioscope and see the pigment stuck in the trabecular meshwork.

P:  Are the onset and progression of pigmentary glaucoma typically slow?

Dr. Rick Wilson:  Yes, a patient would normally have PDS for some time before glaucoma develops.  The glaucoma would typically start slowly.

Moderator:  Will you please explain what a gonioscope is and what the trabecular meshwork is?  

Dr. Rick Wilson:  A gonioscope is a mirrored device that enables the doctor to see into the angle of the eye.  The trabecular meshwork is the meshwork over the canal taking fluid out of the eye

P:  Doesn't PG often burn out over time?  

Dr. Rick Wilson:  The natural history of pigmentary glaucoma is that it turns into open-angle glaucoma.  As we age, the pupil becomes smaller and the lens in the eye become larger.  That leads to more iris-lens touch and pushes the iris forward off the ligaments, decreasing the dispersion of pigment.  The cells lining the drain gradually remove the pigment, so that the patient looks like the usual open-angle glaucoma patient.  

P:  Would lens removal, drastic as it sounds, help to remedy the problem?

Dr. Rick Wilson:  If it got rid of the ligament-iris touch, it would stop the dispersion of pigment.  

P:  Can you have two types of glaucoma at the same time?  For instance, can you have angle-closure glaucoma and then develop a secondary glaucoma like pigmentary glaucoma?

Dr. Rick Wilson:  Yes, you can.  You can, for example, have a common open-angle glaucoma and have trauma or inflammation, adding another cause of glaucoma.

P:  Do you recommend iridotomy for all or for any pigmentary case?  

Dr. Rick Wilson:  Only for those who have a definite posterior curve to the iris that pushes the iris back onto the ligaments (called zonules).

P:  Is a Krukenberg spindle usually present in pigmentary glaucoma?

Dr. Rick Wilson:  Yes.  A Krukenberg spindle is the spindle, or vertically shaped clump of pigment, that layers out in the center of the inside lining of the cornea.  

P:  Does the pigment comprising the Krukenberg spindle have any long-term toxicity for the cornea?

Dr. Rick Wilson:  It doesn't seem to. I have never seen any decompensation of the cornea caused by Krukenberg spindles.

P:  Can you explain how the dispersed pigment causes dysfunction at the trabecular meshwork?  I've read that the "clogged drain" analogy, although intuitive, doesn't really hold  --  that the pigment doesn't so much clog the drain as damage the framework of the trabecular meshwork.  

Dr. Rick Wilson:  The cells lining the trabecular meshwork, as the theory goes, engulf the pigment to get rid of it.  If there is too much pigment, however, the cells die and there is nothing to control the additional build-up of pigment till the trabecular meshwork is mechanically clogged.

P:  Is PG treated any differently than other glaucomas?

Dr. Rick Wilson:  A hole in the iris (peripheral iridectomy) can reduce the iris-ligament touch.  Laser trabeculoplasty is done much earlier in pigmentary glaucoma patients than in normal open-angle glaucoma patients.

P:  Do you think that strenuous exercise necessarily has to be accompanied by head movements to cause excess pigment dispersion?  I read that 10 minutes of stationary biking caused pigment showers (in two subjects with PG).  It was thought that perhaps the release of pigment was the result of elevated ocular pulse, not necessarily jarring head movements, as is usually thought to be the case.  My question is not theoretical,  since I stopped running specifically because of my PG.

Dr. Rick Wilson:  I didn't see that article.  The usual teaching is that the lens is slightly loose in the eye, and movements, especially abrupt ones, cause the ligaments to rub against the back of the iris.  That contact can be prevented by using a drop of pilocarpine before exercise.  The pilocarpine might make your vision blurry, but should prevent the pigment dispersion.

P:  Are there any recent studies on pigmentary glaucoma? 

Dr. Rick Wilson:  There are studies that show it may be hereditary, but I don't know of any recent studies of importance.

P:  Can the clinician determine when the trabecular meshwork has been irreversibly damaged by the constant insult from pigment?  I'm 52 years old, probably just undergoing presbyopia. My obvious worry is that even if the age-related anatomical changes (that you've already described) cause pigment dispersion to cease, the trabecular meshwork may already be too damaged to function properly, even in the absence of continued dispersion of pigment.

Dr. Rick Wilson:  A good yardstick of trabecular meshwork functioning is your intraocular pressure.   If it is normal, you have not used up your excess capacity.

P:  I understand there are some new studies showing a correlation between high homocysteine and exfoliative glaucoma.  

Dr. Rick Wilson:  Since exfoliation is a systemic disease, it makes sense that there would be some disorder of systemic chemistry.

P:  I recall hearing about a vacuum-like tool used to suction out the pigment.

Dr. Rick Wilson:  That was developed for pseudoexfoliation, but should also help in pigmentary glaucoma.  It was just a cannula, hooked up to vacuum, with a fluid infusion source put into the eye separately.  That way, much of the pigment, or pseudoexfoliation, could be vacuumed from the eye.  The result would not be expected to be long-lived if the pigment dispersion or pseudoexfoliation persisted.

P:  I've seen some papers by Italian researchers in mainstream American journals extolling the utility of Dapiprazole in treating PDS/PG.  Why hasn't anybody else picked up on this?  Is it because it's not as lucrative to the drug companies, compared to beta blockers and prostaglandin analogs?  Or is there a good reason not to use to use Dapiprazole?

Dr. Rick Wilson:  No good reason not to use it unless allergy develops. The drug companies have not packaged it for chronic use, as it is what is called an "orphan drug," one whose usefulness is limited to too few people to make it commercially viable.

P:  Is Dapiprazole effective just for PDS?

Dr. Rick Wilson:  It does not lower the IOP but, like pilocarpine, keeps the pupil small, without the side effects of pilocarpine.   The small pupil and taut iris pull the iris forward, off the ligaments that would knock off the pigment granules.

P:  Besides Dapiprazole and pilocarpine (which won't work because of my lattice degeneration and related retinal problems), are there any other ways of preventing the release of pigment?  I'm on a prostaglandin analog which, while controlling IOP, does nothing to straighten out the iris.

Dr. Rick Wilson:  If you have a large posterior bow to the iris, a laser iridectomy helps, but it is not as effective as pilocarpine.

P:  Have you seen many cases of pigmentary glaucoma in women in their early forties?  

Dr. Rick Wilson:  Not many, but a fair number.  It's much more common in men. 

End of highlights for August 13, 2003.

On August 20, Dr. Wilson discussed "Medications" in the Chat room. Click here for highlights of that meeting.

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