Chat Highlights
The Role of Blood Flow and Glaucoma
April 19, 2000

Norma Devine, Editor

On Wednesday, April 19, 2000, Dr. George Spaeth, a glaucoma specialist at Wills, and the glaucoma chat group discussed "The Role of Blood Flow and Glaucoma."  

Moderator:  Hello, Dr. Spaeth.  The topic tonight is Blood Flow and Glaucoma.

Dr. Spaeth:  Okay.  Here's a true story.  About 1968, I wrote the first major book on blood flow in glaucoma.  It was reviewed very critically, because nobody believed blood flow played a role in glaucoma.  I showed then that there are some cases in which it does play a role and some in which it doesn't.  That's really about where we are now, except now everybody is trying to explain EVERYTHING by blood flow, which is crazy.

P:  So part of having glaucoma is having poor blood flow to the eye?

Dr. Spaeth:  Yes, part of some glaucoma is having poor blood flow to the eye.  Selectively increasing blood flow to a small area such as the brain is VERY tough to do. What's the take-home message?  The body can't be split up into separate parts as if each were separate.  All the parts work together.  The best way to improve blood flow to the eye is to improve blood flow to everything!  How do you do that?  First, have good genes.  Next, don't be overweight.  Next, exercise every day.  Next, think positive thoughts, don' t smoke, etc.

P:   Do positive thoughts really help?  Conversely, does stress harm the blood flow?

Dr. Spaeth:   Positive thoughts really help. People faint just from becoming anxious.  People faint because all of a sudden they don't get enough blood flow to the brain.  Those are obvious examples, but there are thousands.

P:   How about stress?

Dr. Spaeth:  Stress is a great but overused and misunderstood word.  The bones would dissolve if they weren't constantly stressed.  We need tension in our lives to live.  But if the bones are stressed too much they break.  What most people mean by stress is something they don't like.  Some people thrive on challenges and others get buried.  The personal response is critical.

P:  By stress I mean worry and anxiety.

Dr. Spaeth:  Yes, but worry is internal.  No situation or person makes you worry or have anxiety.  Those are our own personal responses.

P:  Is there a relation between blood flow and aqueous humor flow?

Dr. Spaeth:  There's almost no relation between blood flow and aqueous humor flow.  The eye pressure goes up and down a few mm Hg each heartbeat.  The major issue is the stability of the blood pressure.  You don't want to take meds that lower BP suddenly or markedly.

P:  I have read that too low a blood pressure or a sudden drop in blood pressure can be harmful to the optic nerve.  What is considered too low and what is meant by a sudden drop?  Is a sudden drop from too high a blood pressure to a normal blood pressure with medication possibly harmful?

Dr. Spaeth:  Lowering blood pressure within a day more that about 50 mm Hg systolic or 20 mm Hg diastolic is not ideal.

P:   Does low systolic pressure have a different effect on the optic nerve than low diastolic pressure?

Dr. Spaeth:   The diastolic is the more important.

P:   What diastolic pressure might be considered too low?

Dr. Spaeth:   A too-low diastolic would be a blood pressure around 50 or so when it had been 80 or so.

P:   If during a long surgery, not for glaucoma, a patient was down to two pints of blood and it was not discovered until the next day, wouldn't that damage the optic nerve?

Dr. Spaeth:   Yes, it could.  It depends on whether the blood loss was associated with a sudden drop of blood pressure.

P:   Are there some blood pressure medications that are worse than others for the glaucoma patient? 

Dr. Spaeth:  It's usually the dose and the response of the patient rather than the specific drug.  There's some (poor) evidence that some of the calcium channel blockers (nifedipine) can help blood flow to the eye. 

P:   Why is it not routine for the eye doctor to take patients' blood pressure during a check up?

Dr. Spaeth:   Because usually it's pretty stable, and because the doctor is usually so far behind he/she does only the essentials.

P:   Please explain calcium channel blockers.  Could it be helpful to take them with Normal Tension Glaucoma (NTG)?

Dr. Spaeth:  Calcium channel blockers are a group of medications that partially block the way calcium moves in and out of cells.  Since calcium is needed for muscle contraction and since muscle contraction (the small muscles that surround the blood vessels) causes blood pressure to rise, decreasing the contractility of the muscles can lower the blood pressure.

P:  So patients on calcium channel blockers need to keep a close watch on their blood pressure?

Dr. Spaeth:  Yes, because calcium channel blockers are two-edged swords.  If they lower the blood pressure too much, they DECREASE the flow of blood to the eye.

P:   Then they are not particularly helpful for NTG.  I also have low blood pressure.

Dr. Spaeth:  Now there is a type of glaucoma that occurs in which the pressure in the eye is average.  Some people call that "normal," but it is not normal in the sense of healthy.  It is just normal in the sense of average.  That "average-pressure" glaucoma has as one of its causes problems other than the IOP alone.  In some, it is related to too little blood flow.  Taking calcium channel blockers can theoretically help some people.

P:   I was asking because that's what I have, but I also have low blood pressure.  Should I ask my doctor about calcium channel blockers?

Dr. Spaeth:  Yes, do ask.  I do not use the calcium channel blockers myself, because there is no evidence they help actual glaucoma in whites.  They probably do help some Japanese patients.

P:  Since there's a high rate of NTG in Japan, is the research done there applicable here?

Dr. Spaeth:   Probably not. The Japanese average pressure is only about 12, whereas ours is about 15.  Thus, they start with lower IOP.  Also, their IOP gets lower as they age while ours gets higher. It' s almost like two different diseases.  The critical question for all glaucoma patients is, what is the effect of this treatment on ME, not on a population.  If you are a smoker, or overweight, or a runner, etc., the same drug may act very differently on you.

P:   I had needling in my right eye in February and a trabeculectomy on April 13, 2000.  My pressure is now at 22.

Dr. Spaeth:  My experience is that needling is not good. It may be the best next step, but if you need a needling you have shown that the eye wants to heal, and healing is what you DON'T want for glaucoma.

P:   How many needlings can one have?

Dr. Spaeth:   Endless.

P:   Last year I had a trabeculectomy in my left eye and it felt like the doctor was scratching the bleb area with a needle, because IOP was too low.  Was that a needling?

Dr. Spaeth:   Sometimes the bleb is too thin and there is too much leakage so the IOP is too low.  One way to treat that is to irritate the conjunctiva to make it get thicker.  Perhaps that's what was being done

P:  Yes, I think that was what happened.  The bleb was leaking.

P:  What is needling?

Dr. Spaeth:   The common surgery for glaucoma makes a small hole in the surface of the eye through which the aqueous (fluid) leaks.  It pools under the thin surface coat of the eye, the conjunctiva.  Sometimes the conjunctiva gets thick and the aqueous gets trapped there and makes a cyst and the IOP rises again.  A needle is intended to cut open the edges of the cyst and get the fluid flowing under the rest of the conjunctiva again.

P:  After surgery on April 13, my IOP was 28, so the doctor cut a stitch.

Dr. Spaeth:   How was the stitch cut?

P:  The stitch was cut with a laser.

Dr. Spaeth:   Usually you design the surgery so that the pressure is higher in the immediate post-operative period than you want for the long term.  Thus, cutting a stitch is not usually a sign that things didn't go well, but rather the other way.  One of the discouraging things about most glaucoma surgery is that the vision is usually blurred, and the eye is bloody looking for about a week.  Then things gradually start clearing up. Something such as a "good bleb" can look good to the doctor and bad to the patient.

P:   We have several patients in the group, one from Brazil, who suffered hypotony maculopathy.  How long can that continue before it's too late to try to remove the wrinkles, etc?

Dr. Spaeth:  As long as it lasts. Hypotony is a bad word though.  Low IOP can be good or bad.  If low IOP is associated with pain or poor vision it usually needs to be treated.  If you have wrinkles in the retina, you probably want to get rid of them.  That usually means you have to get the IOP higher.

P:  I had my "wrinkles" for over a year.  Now with higher pressure, they are GONE!

P:  I thought that IOP caused damage to the optic nerve.  Am I understanding that low blood flow causes this?  Or is it a mixture of both?

Dr. Spaeth:  Low blood flow can cause damage when there is a rapid change, as when a person loses three quarts of blood.  But considerations about blood flow are still theoretical.

P:   I thought so, but I thought I was hearing low blood flow was the only thing.  Sorry.

Dr. Spaeth:  IOP causes damage by many different mechanisms.  The IOP can push the nerve fibers out the back of the eye, almost literally, and damage them.  The IOP can compress the nerves and damage them.  The IOP can stretch blood vessels and cause them to constrict, thus decreasing blood flow and starving the nerves.  The IOP can compress the blood vessels and thus decrease blood flow, etc.

P:  Are there any contraindications for Prinivil and Atenolol for people with glaucoma?

Dr. Spaeth:  Not specifically.  They can actually lower IOP and help that way, but they can cause damage if they cause the BP to drop through the floor.

P:  My husband has glaucoma pretty bad and was having a lot of pain in his eye.  The doctor did a cornea implant to ease the pain and discomfort.  The surface healed 50% and stopped. It has been almost six weeks and it' s still not healing.  The doctor can't understand why.  Could the glaucoma be stopping it?

Dr. Spaeth:  Corneal transplants in glaucoma are tough.  If the pressure goes up after the transplant, it often ruins the transplant.  But if the pressure stays okay, the glaucoma itself is not the cause of the problem.

P:  Why would someone with glaucoma need a corneal transplant?

P:  I will probably have to have a corneal transplant because of my ICE (Irido-corneal-endothelial) syndrome.

P:  I had laser surgery and the pigment clogged up the holes.  I am having a trabeculectomy next week.  Could pigment clog that up, too?

Dr. Spaeth:  No.

P:  I am overweight and lazy.  Is it actually possible to strengthen my eyes by getting my blood flow going?

Dr. Spaeth:  Maybe, yes!

P:   A speaker at a conference at the University of Iowa said the earliest documented medical use of cannabis was stress reduction.

Dr. Spaeth:   Cannabis is like alcohol.  The use of alcohol lowers IOP, but it also has damaging effects, especially in some people such as most Orientals who don't have the enzyme to "digest" alcohol.

P:  Does marijuana have an effect on blood flow to the eye?

Dr. Spaeth:   Marijuana may decrease blood flow to the eye because it lowers systemic blood pressure more than it lowers eye pressure.

P:   After recovering from surgery, what is the effect of exercise on the release of pigment?

Dr. Spaeth:   If you start exercising, do it gradually and for fun.  Otherwise, it's just like marijuana: It won' t really work.

P:   Have you ever heard of a decrease in the IOP after a blood injection?  If so, why would that happen?

Dr. Spaeth:   Do you mean a blood injection into the bleb?

P:   Yes, into the bleb.

Dr. Spaeth:  Yes. You can make a hole in the bleb with the blood injection, and that would make situations worse.

P:  I was asking a patient here about her lower pressure after the blood injection.  She said they couldn't tell if the bleb had a hole in it or not.

Dr. Spaeth:  Bleb holes do repair themselves.

P:  Can I overdose on eye drops like Trusopt, Betopic S, Isopto Carpine, Xalatan.  That is, if I think a drop may not have gotten into the eye, is it okay to give it another just to be certain?

Dr. Spaeth:  If you miss the first drop, use the second, but be sure you occlude the puncta.

P:  Occlude the puncta?

P:  Punctal occlusion. Gently hold the tear ducts closed for three seconds.

Dr. Spaeth:  Make sure every time you use a drop that you push a tissue into the corner of the eye next to the nose to prevent the drop from running down into the nose.  That's important.

P:  What is the significance of a small hemorrhage on the optic nerve in an eye that has no trabeculectomy, has an IOP of 15-17, and a lens implant?  Is this a cause for concern?

Dr. Spaeth:  Yes, a hemorrhage on the optic nerve is almost always a sign that the glaucoma is getting worse.

P:   I had the aqueous shunt procedure and now my eyelid droops.  Do you know if any sort of eye exercises would help lift the lid?

Dr. Spaeth:  You are probably stuck with it. Wait.

P:   Will the lid droop again if the glaucoma gets worse or more I have more surgery?

Dr. Spaeth:  The droop is not related to glaucoma, but there is a relation to surgery.

P:  Some plastic surgeons specialize in lid lifts, don't they?

Dr. Spaeth:  The best are oculplastic surgeons.

P:  Why would a lid droop before surgery?

Dr. Spaeth:  Before surgery it could be due to weak muscles, irritation from drops, neurological disease, etc.

P:  Could plastic surgery for lid droopiness in any way affect the glaucoma?

Dr. Spaeth:  It can if the cause for the droop is a big, thin bleb.

P:  My doctor said that Propine, for instance, can make the eye open farther than normal.  So if it is only used in one eye, it makes the other eyelid appear to be drooping.

Dr. Spaeth:  That's true.

P:  I am just learning about glaucoma.  My eight-year-old grandson was just diagnosed with it.  His pressure was 38.  What you can you tell me, please?

Dr. Spaeth:  Glaucoma in kids is usually very different from that in adults.  Blood flow is one of the reasons.  It is extremely rare for kids to get optic nerve damage related to intraocular pressure (IOP), unless the IOP is really high, like 38.  They almost never get average IOP glaucoma.

Moderator:  Thanks for joining us Dr. Spaeth!

Dr. Spaeth:   Good night.

End of highlights for April 19th chat.

Click here to read more about Understanding the Role of Blood Flow in Glaucoma.

On April 26th , Dr. Wilson discussed Medications and Side Effects in the Chat room. Click here for highlights of that meeting.

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