Pigmentary Glaucoma
Chat Highlights
May 19, 2004

On Wednesday, May 19, 2004, Dr. Elliot Werner, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Pigmentary Glaucoma."

Moderator:  Dr. Werner, the topic tonight is pigmentary glaucoma.  What is the difference between pigmentary glaucoma, pigmentary dispersion syndrome, and pseudoexfoliation syndrome?

Dr. Elliot Werner:  Pigmentary glaucoma (PG) results from pigmentary dispersion syndrome (PDS), in which excessive amounts of pigment literally fall off the back surface of the iris.  The pigment particles float around in the aqueous fluid and get stuck on various structures in the front part of the eye, including the cornea, lens, iris, and the trabecular meshwork in the angle.  The pigment clogs the trabecular meshwork, causing the eye pressure to go up, producing the glaucoma.

Moderator:  What makes pigment fall off the back of the iris? 

Dr. Elliot Werner:  An anatomic anomaly that causes the iris to rub on the lens zonules, which are found just behind the iris.  The iris in PG patients is abnormally displaced backwards (posteriorly, as the doctors say).

P:  How common is pigmentary glaucoma?

Dr. Elliot Werner:  Not terribly common, but not rare. There aren't any good population studies that address this question, but if an eye doc is seeing a younger, predominantly white population, PG comes up fairly frequently.  It is certainly less common than primary open-angle glaucoma (POAG).

P:  How is pigmentary glaucoma diagnosed?  What are the indications?

Dr. Elliot Werner:  The diagnosis is based on the typical appearance of excessive pigment particles seen on the back surface of the cornea and in the trabecular meshwork, as well as characteristic depigmented areas of the iris.

P:  Could glaucoma be pigmentary and open angle at the same time? 

Dr. Elliot Werner:  PG causes an open-angle glaucoma, but it is not POAG.  There are many types of open-angle glaucoma.  PG is one of them.

P:  Are middle-aged males more susceptible than others to PG?  

Dr. Elliot Werner:  PG is most commonly found in white, nearsighted males between the ages of 20 and 45 years, but can occur in males or females of any race, at any age.  The usual age of onset is between 20 and 45 years.

P:  Is race more of a factor in PG than in other glaucomas?   

Dr. Elliot Werner:  Yes, PG is most common in whites; very uncommon in African-Americans or Asians.

P:  Is SLT (selective laser trabeculoplasty) as effective for pigmentary glaucoma as ALT (argon laser trabeculoplasty)?

Dr. Elliot Werner:  SLT and ALT tend to work well in PG because laser trabs work better in heavily pigmented angles.

P:  Is there a consensus about treatment for PG?  

Dr. Elliot Werner:  Most people would probably opt for ALT or SLT as a primary or an early treatment.  Some would prefer medical treatment with any of the usual agents, but there is no overwhelming consensus.  For PG, I prefer to offer laser trabeculotomy, as opposed to medication for POAG. 

P:  I was diagnosed late, at age 47, with cup-to-disc (c/d) ratios of 0.9.  Is it too late for laser iridotomy to be effective?  Wouldn't the procedure release a large amount of pigment, leaving me worse off than before?

Dr. Elliot Werner:  The laser iridectomy lifts the iris off the lens zonules.  It is the rubbing of the iris on the lens zonules that causes the shedding of pigment from the angle.  The iridectomy reduces that, but does very little for already established glaucoma. In early cases, however, it can significantly reduce the amount of pigment being dispersed into the anterior segment of the eye.

P:  If you had a PG patient with a .9 c/d ratio, what target IOP (intraocular pressure) would you aim for?

Dr. Elliot Werner:  That would depend upon what the IOP was before treatment.  For moderately advanced disease, probably a 40 to 50% drop from pre-treatment levels.

P:  With a .9 c/d ratio, do you think an IOP of 18 mm Hg is low enough if the IOP at diagnosis was 36 mm Hg?

Dr. Elliot Werner:  I think a pressure reduction of 36 to 18 mm Hg is a pretty good response.  I would follow such a patient and only get more aggressive with treatment if the disc or field showed progressive change.

P:  Can exercise dislodge more pigment in people with PG? 

Dr. Elliot Werner:  Some PG or PDS patients get what is called pigment storm with vigorous exercise.  They shed large amounts of pigment and develop markedly elevated pressures and blurred vision.  If that is a problem, you may have to limit exercise.   Not all PG patients, however, have this problem. 

P:  What is the prognosis for someone with PG?  

Dr. Elliot Werner:  Generally, pretty good.  Most patients respond well to laser and/or medical treatment.  As with any other glaucoma, early diagnosis is generally associated with a better prognosis.

P:  Can a person with PG have cataract surgery?

Dr. Elliot Werner:  Yes.  It usually doesn't cause significant problems.  In fact, the cataract surgery usually helps to reduce the pigment shedding because of the alteration of the anatomy.

P:  My chart says I have grade 4 angles. What does that mean? Is the scale 1 to 5?  

Dr. Elliot Werner:  Grade 4 means the angles are widely open.  The scale runs from 0 (closed) to 4 (wide open).

P:  I thought the scale for the angles was alphabetical, not numerical.  Is there another scale that uses A, B, C, D?

Dr. Elliot Werner:  There are several classifications for grading the angle.  The previous question mentioned grade 4, which is probably the Schaeffer classification that uses 5 grade levels,  0 to 4, as I mentioned.  The Spaeth classification uses a combination of letters and numbers, which is where the A B C D E comes in.

P:  Which are the best eye drops for PG?

Dr. Elliot Werner:  There is no such thing as the best drop for any glaucoma.  The best drop is the one that works and produces no side effects.  That will vary from patient to patient.  A lot of glaucoma treatment is trial and error.  Either a prostaglandin, beta blocker, or adrenergic is generally used in PG.

P:  I've seen some papers by R. Ritch, et al. suggesting that in addition to the physical contact between the iris and lens/zonules, there's probably some inherent, fundamental defect in the iris pigment epithelium in PG patients that causes pigment to be much more susceptible to liberation, all other things being equal.  Is this a view that has much currency, and what are its practical ramifications for therapy and prognosis?

Dr. Elliot Werner:  Ritch is probably correct, but it is a difficult thing to study because there is no animal model.  Until the mechanism of the pigment release is truly understood, we're unlikely to come up with better and more specific treatments.

P:  Can PG/PDS be aggravated by anatomical changes in the eye, such as presbyopia (difficulty seeing objects close-up)?

Dr. Elliot Werner:  PG generally gets better with age.  Presbyopia actually seems to help, because the lens gets thicker and less mobile, so there is less movement against the iris.  The iris also becomes stiffer and less mobile with age, so the pupil moves less.  All of that helps reduce the pigment shedding as PG patients get older.

P:  I have heard the term "Krukenberg spindles" in connection with PDS.  Could you please explain what these are? 

Dr. Elliot Werner:  K-spindles are characteristic deposits of pigment on the back surface of the cornea in PDS and pigmentary glaucoma.  They have a spindle shape.

P:  Do Krukenberg spindles resolve after pigment release abates?  Do they cause any long-term toxicity to the cornea?

Dr. Elliot Werner:  The spindles do go away if the pigment shedding stops.  As far as we know, they don't cause any significant dysfunction of the cornea

P:  Now that Ocuserts are no longer available, what is the primary course of treatment to reduce or stop pigment release?

Dr. Elliot Werner:  Pilocarpine drops can be used instead of Ocuserts, but the side effects can be troublesome.  Most people now would probably opt for a laser iridectomy to reduce the pigment shedding.

P:  What are Ocuserts and why are they no longer available?

Dr. Elliot Werner:  Ocuserts were little plastic discs that were loaded with pilocarpine.  You inserted one under your upper eyelid for a week and the discs slowly released the pilocarpine.  You got a constant effect with minimal side effects.  The manufacturer stopped making Ocuserts because they weren't making any money.

P:  Can you tell clinically (as opposed to post mortem) the point at which the trabecular meshwork has become irreparably damaged by heavy pigment, rendering interventions aimed at mitigating pigment release pointless?

Dr. Elliot Werner:  Generally, if the IOP is significantly elevated and there is significant optic nerve damage, you've probably reached that stage.  The iridectomy seems to work best before significant glaucoma has developed

P:  If anyone is interested, there is a lot of information about pigmentary glaucoma at http://www.glaucoma.net/nygri/education/tablecontents.html.

P:  I've seen mention of the utility of Dapiprazole in PG, since it acts on the iris dilator muscle (as opposed to the ciliary muscle) and therefore doesn't place traction on the retina, a concern for people like me with lattice degeneration, etc.  But the literature is limited to some Italian researchers.  Why hasn't this idea been taken up by more people, since it's so absolutely intuitive and Dapiprazole has been in use so long, albeit for other purposes?

Dr. Elliot Werner:  Dapiprazole theoretically would work by paralyzing the pupil and preventing iris rubbing.  I'm not sure why it hasn't caught on here.  Dapiprazole is very expensive, fairly short acting, and we have no information of the effect of chronic long-term use.

Moderator:  Okay.  That is all the questions for this evening. 

Dr. Elliot Werner:  Did Dr. Rick tell you the Wills Chat room is going to be honored by the International Glaucoma Society at this year's meeting of the American Academy of Ophthalmology?

Moderator:  No, he didn't. That's good news.  Thank you, Dr. Werner. 

End of highlights for May 19, 2004.

On May 26, Dr. Wilson discussed "Ex-PRESS Mini-Shunt" in the Chat room. Click here for highlights of that meeting.

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