Who is at Risk for Glaucoma?
Chat Highlights
July 19, 2006

On Wednesday, July 19, 2006, Dr. Jeff Henderer, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Who is at Risk for Glaucoma?"

Moderator:    Welcome back to chat, Dr. Henderer.

Dr. Jeff Henderer:    Well, I'm glad to be here!

Moderator:   Tonight we would like to discuss who is at risk for glaucoma.  How does aging affect the risk for glaucoma?

Dr. Jeff Henderer:   It is true that the prevalence of glaucoma (the number of people with the disease) increases as we get older.  Why that happens is unclear, but it seems that for most people, the IOP (intraocular pressure) increases with age.  Perhaps that is why.

Moderator:   What are some anatomical abnormalities that put people at risk for glaucoma?

Dr. Jeff Henderer:   For most people with glaucoma, there is nothing "wrong" with the eye.  You can't see any problem, although we believe that the trabecular meshwork is not allowing adequate flow of the aqueous humor.  Some people have obvious problems, like pseudoexfoliation or pigment dispersion or ocular inflammation, which can raise the IOP.  Others have new blood vessels in the front of the eye that clog the meshwork.  But for primary open-angle glaucoma, there is no obvious defect.

P:    As I well know, eye injury can put a person at risk for glaucoma, sometimes many years later.

Dr. Jeff Henderer:   Good point. Trauma can damage the meshwork and make it less efficient.  So can chronic angle-closure, as the iris gradually obstructs the meshwork. Dr. Spaeth teaches us that looking at the meshwork can tell you what type of glaucoma is present, which is fundamental in any glaucoma eye exam.

P:   How could looking at the trabecular meshwork help a doctor distinguish between, say, primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG)?

Dr. Jeff Henderer:   What Dr. Spaeth is referring to is the most fundamental distinction in the glaucoma types – open- angle and closed-angle.  POAG and NTG are both open-angle and will look the same gonioscopically.

My own belief is that there is no such thing as NTG.  There is simply glaucoma, and the disease is a function of how the nerve can withstand whatever IOP it is exposed to.  Some people are born with stronger structural nerves, and they can withstand elevated IOP.  Some are born with weaker structural nerves, which wither even when exposed to normal IOP.  But that's my hunch. I have no data to support it.

P:   Then what are the differences in the trabecular meshwork for different types of glaucoma?  And can the state of the meshwork be a predictor for glaucoma other than in the obvious cases of pigment dispersion syndrome?

Dr. Jeff Henderer:   Yes, if the angle is closed, you are up a creek.  If the angle is open, it might be heavily pigmented, as in pigment dispersion or exfoliation.  Or you might see blood vessels in the angle.

P:   What is plateau iris?

Dr. Jeff Henderer:   In plateau iris, a rare condition, the iris is being "lifted" from behind by the ciliary body.  That pushes the iris up against the meshwork and can close the angle.  That's a type of angle-closure glaucoma.

P:   Does the typical examination by an optometrist include an examination of the trabecular meshwork?

Dr. Jeff Henderer:   In my experience, that is highly variable.  I'd say that some younger OD's (doctor of optometry) do perform gonioscopy (at least they refer to me for narrow angles), but it is probably not the routine.

P:   Are there certain ethnic groups of people that are at increased risk for glaucoma?

Dr. Jeff Henderer:   We know that for open-angle glaucoma, Africans and African-Americans are at higher risk.  It appears that Hispanics and Asians are roughly comparable to Caucasians.  The general number to remember is that 2% of the U.S. population over the age of 40 has glaucoma and only about half know it.  It appears that other populations are more at risk for angle-closure, especially the Chinese.

P:   How widespread is glaucoma in people under the age of 40?

Dr. Jeff Henderer:   It’s not very common.  There is a peak at birth and at a very young age, then it's relatively uncommon in early mid-life.  It’s much more common beyond age 40 (African-Americans) and age 60 (Caucasian-Americans).

P:   Does glaucoma “run in the family”?

Dr. Jeff Henderer:   Glaucoma does have a genetic component.  Five or six genes have been identified for open-angle glaucoma.  There is a likely gene for exfoliation and pigment dispersion.  Genes have also been found for juvenile and infantile glaucoma.  I'm pretty sure we haven't identified most of the genetic defects in glaucoma.

P:   Is the risk for glaucoma just as high if a grandparent had glaucoma but neither parent did?

Dr. Jeff Henderer:   Well, I would consider it a risk factor.  Perhaps the gene is recessive and skipped a generation.

P:   Do the genes that have been identified in glaucoma predispose a person to glaucoma indirectly (that is, by manifesting in risk factors, such as elevated IOP) or directly (such as a function of some innate defect in the optic nerve)?

Dr. Jeff Henderer:   The short answer is, we don't know the answer for almost all of the defects.  To my knowledge, only two genetic defects have been worked out to the protein-product level.  One, myocilin, probably causes elevated IOP (but not in all patients!), and one, optineuron, is associated with NTG.

P:   I read that glaucoma affects one in 200 people age 50 and younger.  The rate increases to one in 10 over the age of 80.  Does that sound correct to you?

Dr. Jeff Henderer:   Sure. That would be 0.5% for all people age 50 and younger.  The prevalence does increase to almost 10 -15% by the time you reach age 90, so I can believe it.

P:   What kind of medical conditions can increase your risk for glaucoma?

Dr. Jeff Henderer:   Well, diabetes has been linked in some studies.  High blood pressure, migraine headaches, other vasospastic disease, or the use of steroids can raise IOP.  There are also some other, much less common, conditions.

P:   Isn't neovascular glaucoma caused by diabetes?

Dr. Jeff Henderer:   It can be.  Other things can cause it, too, but that's a big one.

P:   Are there any medications that increase the risk for glaucoma?

Dr. Jeff Henderer:   The main medication to be aware of is steroids.

P:   So long-term use of steroids can increase the risk for glaucoma?

Dr. Jeff Henderer:   Yes.  Steroids can raise IOP and also cause cataracts.

P:   Earlier, you said to avoid steroids.  Do you mean completely or prolonged use?

Dr. Jeff Henderer:   Well, prolonged use.  But sometimes steroids are medically necessary. There are some things that are more important than vision.  But if you are given the option of nasal steroids for a cold, think twice. I have seen elevated IOP in as short as a week, but generally I think it takes a bit longer (in the case of eyedrops).

P:   If a glaucoma patient needs a shot of cortisone in a knee, shoulder, or foot, do you think that would increase the IOP much?

Dr. Jeff Henderer:   Probably not.  And as I said, some things (like walking without pain) are more important than the possibility (and not everyone gets elevated IOP with steroids) of a transient rise in IOP.

P:   After trying to avoid a steroid injection in my arthritic foot, I finally had to have the injection yesterday.  My glaucoma specialist said that it was okay for me to have it, yet I am still apprehensive.  What if I need a second one?  Will that be OK?

Dr. Jeff Henderer:   I usually advocate treating the present problem. I do not generally advocate avoiding steroids (unless you are a known responder) for the theoretical risk of elevated IOP.  You should have an IOP check in a couple of weeks and perhaps have a couple checks over the next two to three months.

P:   Is there much danger from occasional use of topical (skin) medications containing steroids?

Dr. Jeff Henderer:   Probably not, but if they are being used around the eye, I've seen it cause elevated IOP.  It's a question of magnitude of IOP rise and duration.

P:   When those medical warnings on over-the-counter medicines say to avoid use if you have glaucoma, does that only apply to POAG?

Dr. Jeff Henderer:   It generally applies to narrow-angles and the risk of causing an attack of glaucoma.

P:   I live in a very rural area and wonder how often my IOP should be checked?

Dr. Jeff Henderer:   I guess that depends on how high your pressure is, how stable the IOP is, and how much glaucoma you have.  Not an easy question to answer, but I guess that, on average, for a stable patient, I generally check one to two times a year.

P:   Does having glaucoma increase the risk for any other medical conditions?

Dr. Jeff Henderer:   Aside from a few rare childhood conditions, I'm not sure that there are other conditions that are connected with glaucoma.

P:   How about low systemic blood pressure?

Dr. Jeff Henderer:   Well, the low blood pressure issue is a tough one.  It's true that there is a relationship, but I think the feeling is that the blood pressure is the cause of the glaucoma, not the other way around.  The big problem is, what can you do about low blood pressure? For those with normal kidneys, you really can't raise blood pressure.

P:   What, if anything, can be done to decrease the risk for glaucoma?

Dr. Jeff Henderer:   Well, almost all of the things we've discussed so far are issues beyond your control (and mine).  Avoid steroids. If you have elevated IOP, you might consider lowering the IOP.  It's not like heart disease, where you can work on blood pressure, cholesterol, stop smoking, and exercise.  We don't have many interventions for glaucoma.

P:   An ophthalmologist once told me glaucoma is a disease of stress.  Do you agree?

Dr. Jeff Henderer:   Stress of the nerve, I guess.  But I’m not sure about stress, as in, “I'm stressed out.”  Perhaps there is a relationship between IOP and emotional stress, but I'm not sure you could ethically test for that. I guess I don't know.

P:   I believe he felt stress restricted blood flow.

Dr. Jeff Henderer:   Could be.

P:   Is it true that vigorous walking can help lower IOP?

Dr. Jeff Henderer:   Yes.

P:   Do animals get glaucoma?  If so, is the rate the same as it is for people?

Dr. Jeff Henderer:   Some breeds and mixed breeds of dogs do get glaucoma. In fact, glaucoma is a leading cause of blindness in dogs. In human beings in the U.S., glaucoma is the second leading cause of irreversible blindness, and the leading cause among African Americans.

[Editor's Note: For information about glaucoma in dogs, cats, and horses, see http://www.animaleyecenter.com/Journals/V1N2.html].

P:   How is the IOP of animals measured?  With a Tonopen?

Dr. Jeff Henderer:   Yes, that's one way.  When I was trying to develop a rat model of glaucoma, we used a Tonopen and a pneumotonometer.  It's not easy!  I'm not sure we ever were able to believe our IOP recordings.

Dr. Jeff Henderer:   Okay, guys and gals! It's my wife's birthday today so I will rejoin the party.  Great to talk to you.  I look forward to this again.  Good night, everyone.

Moderator:   Happy birthday to your wife from all of us.  We look forward to your return.

On July 26, Dr. Wilson discussed "The Cost of Glaucoma" in the Chat room. Click here for highlights of that meeting.

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