Chat Highlights
The Changing Definition of Glaucoma
May 10, 2000

Norma Devine, Editor

On Wednesday, May 10, 2000, Dr. George Spaeth, a glaucoma specialist at Wills, and the glaucoma chat group discussed "The Changing Definition of Glaucoma." 

Moderator:  Welcome Dr. Spaeth.  

Dr. Spaeth:  Thank you. 

Moderator:   Dr. Spaeth, how is the definition of glaucoma changing?

Dr. Spaeth:  Glaucoma used to be easy to define:  It was IOP (Intraocular Pressure) over 21 mmHg.  Now it's a process in which damage occurs to the tissues of the eye in a characteristic way, regardless of the IOP.   Ninety percent of those with elevated IOP never get damage.  Fifty percent of those with damage never have elevated IOP!

P:  So what is damage?

Dr. Spaeth:  Damage comes in different forms to different tissues in the cornea, the iris, the lens, and most important, the optic nerve. Almost everything that can be seen in a normal person can be seen in someone with glaucoma. There is no pregnancy test for glaucoma. 

P:  When do you start treatment? 

Dr. Spaeth:  You treat only when a person is getting worse at a rate that will eventually cause enough visual functional loss that the person will become troubled. Thus, you must know (1) how much damage there is, (2) how rapidly the damage is progressing, and (3) how long the person will live.

P:  If there is no damage to the optic nerve, then no damage can be measured through tests like visual fields.  So how do you know when to treat? 

Dr. Spaeth:  So what is glaucoma?  Did you understand the comment that you first must know if the person is ever going to have functional loss from the glaucoma?   For example, Julia is young, and with a pressure of 40 she will lose function. A person with a life expectancy of two years, a pressure of 40 and a healthy nerve would probably not develop functional loss.

P:  So high pressure is not always bad?

Dr. Spaeth:  No, if the IOP is 50, that's almost always bad; if it's 30, that's sometimes bad; and if it's 20, that's rarely bad.

P:  If 90% of glaucoma patients never get damage, why perform trabeculectomies for open-angle glaucoma?

Dr. Spaeth:  Trabs are done because the damage is getting worse.  Surgery should almost never be done because of a particular pressure level unless, as mentioned, it's about 40 or higher. Recently, a study showed there is more visual loss caused by the treatment for glaucoma than by glaucoma itself. 

P:  Do most glaucoma patients have some damage to the cornea, iris, and lens, in addition to the optic nerve?

Dr. Spaeth:  Patients with angle closure glaucoma can have damage only to the cornea and iris and no damage at all to the nerve.

P:  My IOP was only 15 before the trab. Now it is down to 8. Is it too low?

Dr. Spaeth:  There is no easy answer that fits everybody.  For some, the best IOP would be 25, for some it would be 15, and for some, it would be 10.  It all depends on the person. 

P:  What damage indicates to doctors that it is time to start treatment? 

P:  If there is no damage to the optic nerve, then no damage can be measured through tests like visual fields.  So how do you know when to treat?  

Dr. Spaeth:  You treat only when a person is getting worse at a rate that will eventually cause enough visual functional loss that the person will become troubled. Thus, you must know (1) how much damage there is, (2) how rapidly the damage is progressing, and (3) how long the person will live. 

P:  Do many general practitioners have trouble identifying  glaucoma? 

Dr. Spaeth:  Glaucoma is the process in which the eye becomes damaged in a characteristic way, and the damage is at least partly related to IOP.  (Note, I said to "IOP," not to "elevated" IOP.)  A person who is getting worse with an IOP of 15 is in worse trouble than a person getting worse with an IOP of 30.

P:   Is the person with an IOP of 15 worse off because for some reason he has a more fragile eye structure?

Dr. Spaeth:  You got it!

P:  If there's no damage to the optic nerve, then no damage can be measured with visual fields. So how do you know when to treat?

Dr. Spaeth:  Read what I wrote: (1) How much damage do you have?  (2) How rapidly are you getting worse? (3) How long will you live? Those are the questions that need to be answered. The level of IOP is unimportant.  The hard thing is to change our way of thinking.  That is really tough, but if patients  are to get a fair deal, we all have to do that.  Think that for years, until about 1950  when glaucoma was defined as elevated IOP, 90% of the people being treated were having all the problems of treatment.  But if they had never been treated, they would never have had any damage.

P:  I would like to know how low the pressure should be after a trab and cataract surgery, and then, three weeks later, a synechiolysis.  Is eight all right?

Dr. Spaeth:  There is no answer that fits everybody.  For some, the best IOP would be 25; for some it would be 15; and for some, 10.  It all depends on the person.

P:  If you walk away from a trab, but with wrinkles in the retina and other complications, like a pressure lower than the eye can tolerate, can you still say you don't have glaucoma?  

Dr. Spaeth:  Do you have optic nerve damage?

P:  No.

Dr. Spaeth:  Then you don't have glaucoma.  Why did you have surgery?

P:  My pressures were in the 40's and I am young.

Dr. Spaeth:  A pressure of 40 would certainly cause damage.  So you had the process of glaucoma, but you didn't yet have glaucoma.  The process by which characteristic damage occurs in the tissues of the eye is at least in part related to intraocular pressure. Note:  not to elevated IOP. 

P:  What is the characteristic way the eye becomes damaged in glaucoma?

Dr. Spaeth:  There are characteristic patterns. One is a focal loss of tissue that affects the optic nerve and is associated with a dense loss of visual field that affects only the upper or the lower part of the field. Another pattern is a concentric enlargement of the central "cup" of the optic nerve, caused by asymmetric thinning of the nerve tissue.  Another is a "pit" in the optic nerve.

P:  The textbook of a friend who is taking a medical class defines glaucoma as "elevated intraocular pressure."  If the textbook is so wrong about glaucoma, I wonder how many other mistakes it contains.

Dr. Spaeth:  That definition is just plain wrong.  It is really, horribly, awfully wrong!

P:  If  your doctor treats elevated pressure with medications, then how do you know whether the resultant damage is from medications or from glaucoma?

Dr. Spaeth:  There is no evidence that meds can damage the nerve.

P:  Is it true that most eye drops cause damage to the eye, which in itself adversely affects subsequent surgery?

Dr. Spaeth:  That's a bit too simple.  Meds contain preservatives, and the preservatives tend to be toxic. Thus, if you use them for a long period of time you may irritate or even damage the surface tissues, but not the inside tissues like the nerve. 

P:  Dr. Anderson at Bascom Palmer considers glaucoma not as a pressure-induced disease, but as an optic neuropathy in which IOP is only one of several elements of the pathogenesis. Do you agree?

Dr. Spaeth:  Wrong quote re. Anderson. The second comment is correct.  IOP is only one of the problems in some people.  In others (for example a person with a pressure of 80), IOP is the only problem.

Moderator:  So there is no easy answer to define glaucoma?

Dr. Spaeth:  Not easy, but not hard either. The thing that is hard is the new way of thinking.  I'll say it once again in a different way. If you are not going to get worse, you don't have glaucoma.  If you are not going to get worse at a rate that will hurt you, it doesn't make a  bit of difference whether you have glaucoma or not. We should not treat glaucoma; we should treat the person!

P:  Will you address aggravation of glaucoma by surgery?

Dr. Spaeth:  Trabeculectomies can cause visual loss by causing bleeding, infections, etc.

P:  Do you recommend against laser coagulation surgery for a 59-year-old with an IOP of 36 and 110 degrees of field loss in the left eye?

Dr. Spaeth:  I don't know what 110 degrees of field loss is.  I take it the person has a lot of damage.  Is that what you mean?  If the person has a lot of damage and that damage has occurred at pressures of 36 or lower, then that person will probably get worse.  If the person is going to live long enough for that worsening to be a problem, then the pressure needs to be lowered.  That could mean medications, laser trabeculoplasty, trabeculectomy, cyclodialysis, cyclocryotherapy, cycophotocoagulation, etc.  It depends on the eye and the person.

P:  Is there any way to determine whether vision loss or optic nerve damage is progressing slowly or quickly?

Dr. Spaeth:  Yes.  You look at the optic nerve carefully and determine how damaged it is at each visit, or you measure the field and see if it's getting worse.  Those are the two things you really need to follow. It is important to concentrate on the important issue.  That is, will the person lose function?  That is a really new way of thinking.  The hard thing is to change our way of thinking.  That is really tough, but if patients are to get a fair deal, we all have to do that.  Think that for years (up to around 1950 ), when glaucoma was defined as elevated IOP, 90% of the people being treated were having all the problems of the treatment, but if they had never been treated, they would never have had any damage. 

P:  If an elderly woman is taking medications for high blood pressure and beta-blockers for glaucoma, should she be concerned about interaction between the two?

Dr. Spaeth:  Beta blockers in older people can be a problem.  Yes, she does need to be concerned about interactions.

P:  Unless you wait for a year or two for the visual field to show if you are sustaining any damage, how do you know if you are going to lose function?

Dr. Spaeth:  Super question!  In fact, you don't know.  The only way you can tell for sure that a person is going to get damage is to see the damage develop. 

P:  If a patient has optic nerve damage and vision loss in one eye, and optic nerve damage only in other, and the patient is young, odds are they will eventually lose vision?  Is that the patient that needs treatment now?

Dr. Spaeth:  If the person has damage in one eye and has the usual type of glaucoma, it is likely the other eye will eventually develop damage.  But it may take 10 or 15 years.  So treatment is only appropriate if the person with that rate of damage will live that long.  If the pressure is 50, you can be sure.  But for most people with pressures below 30, you can't predict accurately.  So what do you do?  You document meticulously the nature of the disk (optic nerve) and the visual field and then see if they change

P:  When will the summary of this chat be posted? I would like to share this with my spouse and add to the confusion. 

Dr. Spaeth:  There shouldn't be confusion.  Keep it simple.  The principles are really simple.  Is the person getting worse?  Is the deterioration rapid enough to cause the person to have a deterioration of the quality of life?  Those are the issues.  They are not complex.  But the subject is really at the heart of the understanding and treatment of glaucoma.  What is the disease and what is the purpose of treatment?  It is to keep the person healthy.  The way to do that is to concentrate on the person's health.

P:  How long do you wait for change?  Does the age of the person matter?

Dr. Spaeth:  Not the age, the life expectancy.  An 80-year-old person needs more vigorous treatment than a 50-year old, if the 80-year old is healthy and takes care of herself and the 50-year old is a drinker, smoker and bungee jumper.

P:  Why not go for the most aggressive treatment from the start?

Dr. Spaeth:  Because every treatment carries side effects.  Remember that perhaps more blindness is caused by the treatments than by the disease.

P:  Can you tell me if you think my IOP will be all right at 8?  I don't smoke or drink and am healthy at 67.

Dr. Spaeth:  Are you getting worse? How much damage do you have?  How long will you live?  Those are the three questions that need to be answered.

P:  Does it mean that till the damage is evident, treat it conservatively?

Dr. Spaeth:  By and large, yes!

P:  Discuss the discuss adverse effect of surgery on glaucoma.

Dr. Spaeth:  That's too broad. Surgery comes in many forms.  It depends on the type of procedure.

P:  So you don't treat anyone, even with a family history of glaucoma, until you verify he or she really has glaucoma and the loss will affect his or her life?  

Dr. Spaeth:  You're pretty much on target. In fact, you're right on target!

P:  I have had cataracts in both eyes and detached retinas with buckles and now glaucoma.  I cannot handle any invasive surgery.

Dr. Spaeth:  Laser coagulation can be a good procedure in people who can't handle invasive surgery.

P:  My pressure is 26.  It was 24 after surgery.  I am 59 years old and I have a 110 degree loss in my left eye.  Do you suggest additional surgery?

Dr. Spaeth:  I don't know what 110 degrees of field loss is.  I take it the person has a lot of damage.  Is that what you mean?   If the person has a lot of damage and that damage has occurred at pressures of 36 or lower, that person will probably get worse.  If the person is going to live long enough for that worsening to be a problem, the pressure needs to be lowered.  That could mean meds, laser trabeculoplasty, trabeculectomy,  cyclodialysis , laser cyclophotocoagulation, etc., etc..  It depends on the eye and the person.    

P:  I am using Xalatan in each eye at bedtime.  My IOPs are 23 and 25, I have no nerve damage and my field vision is okay.  Do you recommend taking the Xalatan? 

Dr. Spaeth:  What is your life expectancy?  What's your IOP off treatment?  How much did the Xalatan lower the IOP? 

P:  I don't exactly remember, but  my IOP is slightly higher than when I began the Xalatan.  I am 68 years of age.

Dr. Spaeth:  You're 68 and healthy, I assume.  My preference would probably be to follow you on no treatment, assuming your optic nerve looks healthy.  If your optic nerve is really bad, however, you may need surgery.  Remember, it's (1) how much damage, (2) how rapidly you're getting worse, and (3) how long you live. 

P:  The ophthalmologist always tells me at every six-month check-up that there is no nerve damage.

Dr. Spaeth:   That's super!  First, your doctor is looking at the important thing and second, that's great news.

P:  Doctor, she is being treated for glaucoma, but has no optic nerve damage.  Comments?

Dr. Spaeth:  Sounds like it may be a bit aggressive

P:  I thought you once said, "No optic nerve damage, no glaucoma."  Am I wrong?

Dr. Spaeth:  You are right.  But sometimes you treat because the likelihood is great that glaucoma will develop rapidly.

P:  I was wondering if sometimes they give the drops just to keep the pressure down, even though there is no sign of glaucoma otherwise.  I hate to take those drops if they are not really necessary.

Dr. Spaeth:  Ask your doctor why you need the drops.  That is a fair question to ask!

P:  I had a revised trab.  The pressure went down to 6.  Should I start learning Braille?

Dr. Spaeth:  An IOP of 6 may be good for you.  It depends on the pressure at which you were getting worse, the rate at which you were getting worse, etc. 

P:  My IOP was zero after a trab and cataract surgery.  After I had the Band Aide contact and drank lots of water, my IOP gradually increased from 4 to 12 and down to 9.  After a synechioloysis on Monday, it went down to 8.  Is 8 okay for now? 

Dr. Spaeth:  An IOP of 8 is usually pretty terrific! 

P:  Some of us read your article: "The Surgery Was a Success, But the Patient Died." I liked it very much.

P:  Same here, doctor, regarding the article.  

Dr. Spaeth:  Thanks, and thanks for the great questions and comments.  

End of highlights for May 10th chat.

On May 17, Dr. Rick Wilson discussed "How to Handle Cataracts in Glaucoma" in the Chat room. Click here for highlights of that meeting.

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