Monday Night Chat Highlights
July 2, 2001

Norma Devine, Editor

Dr. Jeff Henderer, a glaucoma specialist at Wills, paid a visit to the Monday night chat room.

Monitor:  Hello, Dr. Jeff.  Welcome!  A new glaucoma patient joined us tonight.  She's 51 years old and would like to discuss her diagnosis.  

P:  Yes, I would, thank you.  Dr. Jeff, I was diagnosed with glaucoma in November 2000.  My intraocular pressures were 24 and 25 mm Hg.   Most of the damage appears to be in the upper part of the visual field in the right eye.  The  optic nerve cupping is .9 in the right eye and .8 in the left eye, with no field loss.  I had had regular optometry appointments annually before, with IOPs (intraocular pressures) under 18 mm Hg.  No one saw the nerve loss or tested the fields. Now there is uncertainty about the kind of glaucoma I have. Originally it was called POAG (primary open-angle glaucoma).  Three glaucoma doctors told me I had narrow angles and recommended peripheral laser iridotomy, which I had done on both eyes in June. The IOP did not change.  Now the doctor says I have plateau-iris syndrome, but he doesn't recommend further laser surgery at this time. I've been using Xalatan in both eyes since December.  I tried Timoptic after the laser iridotomies, but it had no effect. Today I start Alphagan twice a day. Sorry for the long story.

Dr. Jeff Henderer:  Okay, that's not an uncommon length to your story.  Sounds like you are on the right track, even if the diagnosis was made recently.  I'm glad it was made!  Plateau-iris syndrome is a fairly rare thing that can cause angle-closure glaucoma.  It is often watched or treated with laser.

P:  So right now I am being watched!

Dr. Jeff Henderer:  That sounds okay.  If the angle seems to progressively narrow, some  doctors use pilocarpine to open it, and some laser the peripheral iris surface to "heat shrink" the iris and pull it away from the drain.

P:  How long does heat shrinking last?

Dr. Jeff Henderer:  It should be visible forever, but the angle can still narrow,  in which case you may need to repeat it.

P:  What should be visible forever?

Dr. Jeff Henderer:  The laser burns.  They are too small to see without a microscope, though.

P:  Is plateau-iris syndrome more common in females than males?

Dr. Jeff Henderer:  I don't think so. I have about a 50/50 mix in my group of about 8 or 10 patients with plateau-iris syndrome.

P:  Is any particular age group affected?  

Dr. Jeff Henderer:  That's a good question, too.  I think that narrow angles in general are typical of middle age  -- in the 50's is common.  That's when the lens starts to get big enough to crowd the angle.  I just haven't seen much of it in older patients. 

P:  Thanks.  My doctor  today said that he generally sees narrow angles appear later in life (in the 70's and 80's), and he sees plateau-iris glaucoma in the 50's age group.

Dr. Jeff Henderer:  I typically see narrow angles in younger folks, but remember that you really can't diagnose plateau-iris syndrome until after an iridotomy.  I don't know if that plays a role here.

P:  Thank you.

P:  Dr. Jeff, are there "normal" numbers for a GDx (nerve fiber analyzer)?  

Dr. Jeff Henderer:  Normal numbers and the GDx are hard to figure, but I believe the company says that numbers under 30 are okay,  30 to 70 are suspicious, and numbers above 70 are worrisome.

P:  I had a GDx today.   The number for the right eye was 84; for the right eye, 73. 

Dr. Jeff Henderer:  Well, the machine would say that that is glaucoma, which seems to be what the doctors said, too.  

P:  Dr. Jeff, how reliable is the GDx?

Dr. Jeff Henderer:  The GDx is reliable, but not perfect (no test is). 

P:  What kind of information does the GDx provide?  

Dr. Jeff Henderer:  The GDx tells you the thickness of the nerve fiber layer, the layer of nerves on the retinal surface that are damaged by glaucoma.

P:  I'm looking at my GDx report and I don't see these numbers.  This paper has charts with all kinds of numbers. 

Dr. Jeff Henderer:  You look for the "number" in the boxes at the bottom of the printout, and it should be labeled as such.  

P:  Dr. Jeff, before you arrived, we were talking a bit about cup-to-disc ratios, etc.  Is it correct to say that the size of the cup itself doesn't really matter so long as the ratio is .5 or less, or hasn't been changing?  When people talk about "cupping" of .8 or .9, is that the RATIO they are referring to, or just the size of the cup? 

Dr. Jeff Henderer:  Excellent question.  There is really not a "normal" c/d (cup-to-disk) ratio.  It depends a great deal on nerve size.  The fraction 0.8 refers to the c/d ratio.  Very few doctors actually measure the nerve size.  Small nerves have small cups.  Large nerves may even have 0.8 cups and be normal.  

P:  So .8 cup means .8 cup/disc ratio then?

Dr. Jeff Henderer:  Yes, that's correct. If the ratio is not changing, that is good. The real key is the neuroretinal rim.  That is where the attention should be directed.  Thinning of the rim is much more descriptive than a c/d ratio.  

P:  There's a lot of misunderstanding among patients about cup-to-disc ratios, and what they mean.  

P:  Thanks for clearing this up.  I really wish if they mean to say c/d RATIO they would say that.  

Dr. Jeff Henderer:  The optic nerve is a disc with a central depression, the cup.  The overall size of the cup compared to the overall size of the disc is an important feature of glaucoma.  The really important thing, though, is the rim and its thinness. 

P:  Is that the rim of the cup or of the disc?

Dr. Jeff Henderer:  The tissue that is in between the edge of the cup and the edge of the disc is called the rim.  It can be hard to pin down exactly where the boundaries are in all eyes, but it is important to try.

P:  Does the heat of summer bring on any concerns for glaucoma patients and their medications?

Dr. Jeff Henderer:  Yes.  Xalatan cooks in the sun and loses potency.  Don't leave it in your car!  Also, IOP tends to be lower in the summer in Scandinavia. 

P:   Let's all go there!

P:  I have always wondered whether having dilated pupils (large pupils) has anything to do with glaucoma or sight problems.  Do you know of any such connection?  

Dr. Jeff Henderer:  I'm not aware that that would be a problem except in LASIK (laser in-situ keratomileusis).

P:  Do you know what dermato chalasis is?

Dr. Jeff Henderer:  That's excess upper eyelid skin.

Monitor:  Thank you for dropping in tonight, Dr. Jeff.  You really helped the new GlaucoMate from Seattle, Washington, clarified confusion about the meaning of cup-to-disc ratio, and made this an informative session for all of us.  Come back soon.  Happy Fourth of July!

End of chat highlights for July 2, 2001.

On July 18, Dr. Wilson discussed "Glaucoma Shunts" in the Chat room. Click here for highlights of that meeting.

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