Glaucoma Down Through the Ages

Chat Highlights
January 12, 2005

Norma Devine, Editor

On Wednesday, January 12, 2005, Dr. George Spaeth, Director, Wills Glaucoma Service, and the glaucoma chat group discussed "Glaucoma Down Through the Ages."

Moderator:  Welcome to chat, Dr. Spaeth. The topic tonight is "Glaucoma Down Through the Ages."

Dr. George Spaeth:  Thank you.  Maybe I can start things out.  The subject is really important. 

Moderator:  Please do. 

Dr. George Spaeth:  A thousand years ago, glaucoma was "painless blindness." Later it became apparent that most people who were thought to have glaucoma really had cataracts.  About 1850 it became clear that eyes with high intraocular pressure (IOP) were sick, and high pressure became the definition of glaucoma.

About 100 years later, work began which eventually showed that 95% of people with elevated pressure never got glaucoma, and 50% of those with glaucoma had normal pressure.  Wow!  Something was clearly wrong with the old idea that glaucoma was elevated IOP.

Moderator:  What is the thinking now?

Dr. George Spaeth:  Now we think that pressure inside the eye always plays a role in the development of the damage to the optic nerve.  That is the hallmark of glaucoma.  The pressure can be 10 or 15 or 50 mm Hg.

But glaucoma is NOT elevated pressure.  Glaucoma is a process in which the optic nerve changes from healthy to sick.  Some people never get really sick nerves and other people do, but that is not related to the level of pressure.

P:  In the 1800's, how was glaucoma diagnosed and what was the treatment?

Dr. George Spaeth:  Doctors just measured the pressure, and they treated with pilocarpine or similar drugs that made the pupil small.

P:  At a conference last fall, Dr. Robert Ritch said that when he first started practicing medicine, glaucoma had three stages: eyedrops, surgery, blindness. Can you elaborate?

Dr. George Spaeth:  If the pressure was above 21 mm Hg, people got treated; if below 21 mm Hg, they were not treated.  So 95% of the people were treated unnecessarily.  Some people need surgery first, others laser first, others drops first.  The care needs to be individualized.

P:  Since it used to be common to treat patients for glaucoma purely on the basis of elevated pressure, and since a family history of glaucoma is considered a risk factor, how can patients today really know whether their grandparents or other relatives actually had glaucoma?

Dr. George Spaeth:  Great question! You can't.  Most people back then who were told they had glaucoma did NOT have glaucoma.

P:  What do you consider to be the greatest advance in the understanding of glaucoma during the last 50 years?

Dr. George Spaeth:  The understanding that glaucoma is a complex disease, not just high pressure.

P:  How was the difference between blindness due to glaucoma and other diseases, such as macular degeneration, discovered?

Dr. George Spaeth:  It is not difficult to learn to see the type of damage that occurs.  Glaucoma causes the optic nerve to be damaged. In macular degeneration, the macula is diseased.

P:  The chronic open-angle glaucomas have been studied more extensively than any other types of glaucoma, but is more known about the mechanisms of that type than the other types?

Dr. George Spaeth:  No. The best understood glaucoma is primary angle-closure glaucoma.  There the problem is that the front of the eye is small and the iris blocks the drain.  With the chronic glaucomas, we still do not understand why some people get worse and others don't.

P:  At the beginning of the 20th century, doctors had only miotics for the medical treatment of glaucoma.  Pilocarpine, the oldest of today's glaucoma medications, and the prostaglandin, Xalatan, one of the newest, have opposite effects on uveoscleral outflow. Are both drugs effective when used together?

Dr. George Spaeth:  Yes, but not additively.  Some docs don't use them together.

P:  How confident are you that current classifications and concepts of the glaucomas are correct and useful?  Are glaucoma researchers looking for new paradigms?

Dr. George Spaeth:  We are looking for new paradigms.  I have an editorial coming out about them in several months.  It is clear that our present classification system is not adequate.  The difference between open-angle glaucoma and angle-closure glaucoma, however, is valid and important.

P:  Where will your editorial appear?

Dr. George Spaeth:  In the journal "Ophthalmology."

P:  What types of surgeries for glaucoma were available 60 years ago, and how successful were they?

Dr. George Spaeth:  Quite amazingly, the surgery that we do today was started over 100 years ago.  It has been refined and modified, but it is still basically the same thing.  The so-called trabeculectomy is the same operation that was done 100 years ago, except a lid covers the drain.

P:  I recently had cataract surgery, which was vastly different from my mother's cataract surgery.  It's unfortunate that glaucoma surgery has changed so little in all these years.

P:  Was the Scheie sclerectomy an early form of a trabeculectomy?   My Mom had that done 32 yeas ago.

Dr. George Spaeth:  The Scheie procedure was a great operation.   The problem was that it often (about 1/3 of the time) allowed too much drainage.  The front of the eye collapsed, leading to cataract and other problems.  The newer operations put a lid on the drain, which prevents that kind of complication in most people, but results in higher pressures.

Moderator:  When were lasers first used for glaucoma surgery?

Dr. George Spaeth:  Now lasers are new and a great addition.  About 25 years ago, a doctor in Oklahoma found that pressure could be lowered by treating the trabecular meshwork with very low levels of argon laser energy.  That was a great contribution.

P:  Is it fair to say that advances in glaucoma treatments have been slow in the last 100 years?

Dr. George Spaeth:  The changes have really been dramatic, but they have been conceptual.  Think of what it means that what everybody thought was right in l950 everybody now knows is wrong. There are so many misunderstandings.  For example, peripheral vision is the LAST part of vision to be lost.  Also, surgery is often the best first treatment, and so on.

P:  One of those misunderstandings is what "peripheral" vision means.  For instance, the visual field tests I've taken for years on Humphrey machines test the central 30 degrees, not peripheral vision.

Dr. George Spaeth:  That depends upon the type of visual field machine.  Some do test for peripheral vision.

P:  Why isn't the full visual field tested?  Do doctors think that the peripheral loss outside the 30 degrees is acceptable to most of us?

Dr. George Spaeth:  Testing outside the 30 degrees is difficult, and that is not where early field loss develops.  Thus, it would be time consuming and would not tell us anything that we can't learn from testing the more central portion.

[Editor's note:  The central 30 degrees of vision is straight-ahead vision. It is the part you are using to see your computer screen.]

P:  Although the visual field tests are now much less tiring for patients than in earlier years, most patients still dread taking those tests. Do you foresee further advances in that area soon?

Dr. George Spaeth:  I think visual field testing has gone as far as it can.  I predict that the tests we use now will become increasingly less important in the future.  They are too difficult and too nonspecific.  Objective field machines are being developed and they may be a help. That is, the person does not push a button, but just looks at a target.

Moderator:  Which is more important: the cup-to-disc ratio or alterations in the topography of the optic nerve head?

Dr. George Spaeth:  Cup-to-disc ratios are a rough guide.  But the pattern is more important.  You differentiate a Van Gogh from a Monet painting by the pattern, not by the size of the frame.

P:  When my glaucoma was diagnosed in early 1988, I was torn for years between the arguments of mechanical versus ischemic theories.  That debate seemed to end in a blind alley.  Now, Dr. Joseph Caprioli at the University of California, who served a fellowship at Wills, says we have to forget that argument, and think about cellular and molecular pathways.  Do you agree?

Dr. George Spaeth:  Joe Caprioli took his training with me.  He is very bright and knows a lot.  But he is falling into the same trap that affected older doctors.  He is looking for ONE answer. There is no ONE answer.  Some people lose sight because of mechanical damage to the nerve, some because there is not enough blood flow, some because of an abnormal gene, and so on.

P:  What you are saying is not only very informative, but gives me hope.  I am so intimidated by the ophthalmologists I have seen that I didn't dare question the treatment.

Dr. George Spaeth:  The challenge is always to look at the individual person -- who is always different from every other person -- and to figure out what is happening with that unique person.

P:  Doctor Spaeth, we live in an era where many -- both professionals in various fields as well as lay persons -- search for the cures in the causes.  Often it's assumed that if the cause is known, a cure can be found.  I don't see that clearly in glaucoma research. Perhaps there's not much to be gained from the popular methodology. Can you comment, please?

Dr. George Spaeth:  In the 1800s people were dying from cholera in London.  John Snow, an engineer, noted that people died in certain areas and not in others.  He concluded that the water supply caused the deaths, and saved the lives of millions without knowing anything about the fundamental cause.

P:  If the pressure is high and drops won't lower it, but the optic nerve is healthy, is surgery still needed?

Dr. George Spaeth:  If the nerve is healthy, why do you need any treatment at all?

P:  Don't data show that treating ocular hypertensives preserves vision over the long term, as opposed to not treating?

Dr. George Spaeth:  The data are the other way around.  Treating causes cataracts and introduces anxiety.  The only long-term study, by Linner and Stromberg, showed that after 25 years of not being treated, ocular hyptensives rarely (5%) lost enough vision to notice any visual loss.  But everybody who is treated for ocular hypertension has some side effects from the meds.

P:  How accurate are the tools, such as retinal flow meters and color Doppler imaging, for measuring blood flow of the optic nerve?

Dr. George Spaeth:  For populations, they are great.  For individuals, they are almost useless.  If you measure the temperatures of a large group of people, the average temperature is usually around 98.6 degrees.  But some people have temperatures that are above that and others below that.  Some people's healthy temperature differs from what is thought to be normal.  And so it is with everything else, including measurements of blood flow.  Some people go blind with a pressure of 12 mm Hg, and other people need no treatment with a pressure of 30 mm Hg. “Healthy” and “average” are not synonyms, though those who know nothing about life would have us believe they are.

P:  How do you define a healthy optic nerve?

Dr. George Spaeth:  A healthy optic nerve is one that works well.

P:  What tests can help determine if an optic nerve works well (is healthy)?

Dr. George Spaeth:  How well do you see?  How well does the nerve transmit electrical impulses to the brain (tested with VEP)? How well do you see colors, movement, dark objects, etc.?

[Editor's note:  VEP stands for Visual Evoked Potential, a test involving computerized recording of the electrical activity at the back of the brain (occipital cortex) that results from light flashes stimulating the retina.  The test is used for detecting defects of the retina-to-brain nerve pathway, since they can change the brain-wave patterns.]

P:  I read about the equilateral triangle: pressure, visual fields, optic nerve scans.  So far, I have had two optic nerve scans in three years and plenty of pressure readings. Is that approach lopsided?

Dr. George Spaeth:  Field damage usually occurs after nerve damage.   The most important thing is looking at the optic nerve.  The scans are not as good as a good examination of the optic nerve.  You can usually tell if a nerve is healthy by the way it looks.  But it is like looking at a painting.  It is the pattern, not the cup-to-disc ratio or any other figure, that tells you the answer.

P:  When do you think we might expect to see clinical benefits from neuroprotectants and gene therapies?

Dr. George Spaeth:  Neuroprotectants?  We have a great neuroprotective procedure now: lowering the pressure.  From drugs and so on, perhaps never. From gene therapies, right now some gene theories work for other diseases, but for glaucoma, perhaps never.

P:  Do you anticipate an increasing interest in neuroprotective agents independent of intraocular pressure?

Dr. George Spaeth:  Yes, but I think it is misguided.  That was a bad answer.  I think that preserving the health of the nerve by means other than lowering pressure is terribly important, but it may be diet, exercise, chocolate.  Who knows?

P:  Is uncontrolled high pressure always a precursor to optic nerve damage?

Dr. George Spaeth:  Ninety-five percent of people with elevated pressure never get nerve damage.  Fifty percent of people with nerve damage never have elevated pressure.

Moderator:  At what pressure does damage definitely occur?

Dr. George Spaeth:  The answer is that everybody is different and some people get worse at low pressures and others don't.  At pressures above 30 mm Hg, people are predisposed to getting a clot in the veins of the eye.  Therefore, I advise treatment in most people with IOP over 30 mm Hg, not to prevent glaucoma, but to prevent a blood clot.  When the pressure gets to 50 mm Hg, that's almost always bad.

P:  From what you've said, it seems to me that you do not favor the use of medications for the treatment of ocular hypertension, and maybe not even for glaucoma (that is, when damage has occurred).  Please comment.

Dr. George Spaeth:  I favor the use of medications or laser or surgery if it is clear that a person has a condition that will cause visual disability.  If the nerve is normal and staying normal, treatment is rarely needed.  If the nerve is getting worse, treatment is needed in most people.  If the person already has visual disability, treatment is usually essential.

P:  Where does early field loss develop?

Dr. George Spaeth:  That depends on the person.  In some, the earliest field loss is almost straight ahead; in others, it is near the natural blind spot; in others, it is in the nasal periphery.

P:  Do doctors routinely look at the optic nerve at each visit?   Maybe I'm missing that part.

Dr. George Spaeth:  Great question.  The answer is no, but they should look at the optic nerve whenever there is a question about determining the person's visual stability.  Thanks for asking that question.

P:  My eye specialist measures my pressures, then looks into my eyes briefly, and that's it.  Do you think he is looking properly for any changes?

Dr. George Spaeth:  That's the usual approach.  If I had my way, it would be reversed.  Boy!  Will your doc hate me.

P:  I have seen four glaucoma docs and they all cue into the high pressure as a red flag that must be lowered or else optic nerve damage will or could occur.  Why are so many docs fearful of high pressure if 95% of those with it never get nerve damage?

Dr. George Spaeth:  Because that's what we all thought for 150 years.  Habits change slowly.

P:  What has been the result of treating people once their pressures got to 21 mm Hg?

Dr. George Spaeth:  All treatments cause problems.  Eyedrops cause impotence, heart block, gastrointestinal upset, back aches, anemia, death, and more.

P:  I know that the best technology is nothing if not interpreted correctly.  How can you tell if your doc is experienced in recognizing nerve changes?  What questions should a patient ask?

Dr. George Spaeth:  Ask him or her how important examination of the nerve is.

P:  Is it the preservatives in eyedrops, rather than the eyedrops themselves, that have the most side effects?  If so, why don't ophthalmologists insist that preservative-free medications be developed?

Dr. George Spaeth:  Preservatives protect people from getting infections. But preservatives are poisons.  Preservative-free drops are dangerous.  But the preservatives are dangerous, too. It is always a trade-off.

P:  When you began your training, were there many glaucoma specialists in the U.S., and how has that number changed over the years?

Dr. George Spaeth:  When I started training in 1960, there was a handful of glaucoma specialists.  Now every hospital or university has one or more. Wills has 14 glaucoma specialists.

Dr. George Spaeth:  I'm still at work and my wife is holding dinner for me. So I will say good-bye.  I hope I have raised questions.  I hope all of you have a great new year that is healthy and happy.

Moderator:  Dr. Spaeth, thank you for your time.  We look forward to having you back in the chat room again.

Dr. George Spaeth:  We doctors do not know as much as we think we know or as patients believe we know.  If that message comes across, this evening will have been worthwhile.  I know that what I am saying will make some people rethink their whole condition. GREAT!

End of highlights for January 12, 2005.

On January 26, Dr. Wilson discussed "Stages of Glaucoma Progression" in the Chat room. Click here for highlights of that meeting.

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