The Role of Blood Flow in Glaucoma
Chat Highlights
July 13, 2005

On Wednesday, July 13, 2005, Dr. Rick Wilson a glaucoma specialist at Wills, and the glaucoma chat group discussed "The Role of Blood Flow in Glaucoma."

Moderator:  Has the thinking about the role of blood flow in glaucoma changed in recent years?

Dr. Rick Wilson:  I think that circulation has always been a presumed risk factor for normal-tension glaucoma, but we are learning more about how circulation plays a role.

P:  What is pulsatile ocular blood flow?

Dr. Rick Wilson:  With each heartbeat, a pulse of blood is pushed into the eye.  That raises the total blood volume in the eye. Since the eye is an enclosed space, that volume raises the eye pressure for a short time.  The volume of blood that enters the eye can serve as a marker for circulation, and is studied to see if it can be shown to play a role in different kinds of glaucoma.

P:  Do glaucoma patients have a problem with too much blood or too little blood flow or does that depend on the type of glaucoma?

Dr. Rick Wilson:  Most patients, especially those with normal-tension glaucoma, are more likely to have a problem with too low blood pressure, so that blood is not getting into the eye in sufficient quantities or at adequate pressure to nourish the optic nerve.  A few patients have an abnormal connection between their high-pressure arterial system and their low-pressure venous system.  Since the eye fluid drains from the eye into the aqueous veins, if the pressure in the veins is abnormally high, it prevents aqueous from the eye from draining and the IOP (intraocular pressure) rises.

P:  I had a blood vessel break in my eye a month or so ago.  It formed a big blob of blood around the iris, spilled down around both sides of the iris, and filled the bottom of the eye.  It took about 10 days to completely dissipate.  This type of bleeding in the eye is different from bleeding behind the pupil and iris, though.  Does that mean there is nothing to worry about?

Dr. Rick Wilson:  If the blood is on the outside of the eye wall, that is, on the white of the eye, it almost always is of no consequence.  Sometimes, though, it can hurt slightly when it first happens.

P:  If that happens, could the patient see the blood?

Dr. Rick Wilson:  Blood can be seen between the cornea and the iris or lens in the eye by looking in a mirror.  You can often tell there has been bleeding in the jelly of the eye (the vitreous) by the sudden onset of stringy floaters in the vision and a red haze.

P:  Are there tests that I should ask my doctor to perform to check my blood flow?

Dr. Rick Wilson:  We don't really have sensitive and accurate tests for blood flow to the optic nerve.  We can see blood flow to the retina and the surface of the optic nerve by injecting fluorescein into the blood stream and watching it go through the vessels in the back of the eye.  We can't, however, see the blood flow deeper in the nerve.  A color Doppler test can give us an idea of the blood velocity as it goes through the vessels there.

P:  Should patients request fluorescein injections periodically?

Dr. Rick Wilson:  No.  Fluorescein usually is only done for retinal disease.

P:  How do calcium channel blockers and over-the-counter medicines such as aspirin affect eye blood flow?

Dr. Rick Wilson:  In patients who have vasospasm as a problem, (for example, those with migraines or Raynaud's syndrome), calcium channel blockers can lessen the severity.  Unfortunately, in many people calcium channel blockers may also lower blood pressure, which decreases the amount of blood pumped through the nerve to nourish it.  Aspirin is a platelet inhibitor, so it inhibits the clotting function of the blood.  In other words it thins the blood.

P:  How do beta-blockers affect blood flow?  Should patients with normal-tension glaucoma use them to control high blood pressure?

Dr. Rick Wilson:  Beta-blockers usually slow the heart and may lower blood pressure, which would slightly affect circulation.  For most people, this does not seem to be a problem.

P:  Without accurate ways to measure blood flow to the optic nerve, if there is progressive nerve damage, do you mostly infer some vascular insufficiency from the absence of other diagnostic risk factors (like high IOP)?

Dr. Rick Wilson:  We do a vascular workup to make sure there is not atherosclerosis blocking the carotid and decreasing flow to the brain and eye.  We test to make sure the blood pressure is high enough, not only during the day, but also during the hours of sleep.

P:  How do you measure blood pressure when a person is asleep?

Dr. Rick Wilson:  An automated blood-pressure cuff can take your blood pressure as often you like, even while you are sleeping.

P:  What is the best way to increase blood flow to the optic nerves?  Are there new drugs being designed to do that?

Dr. Rick Wilson:  Aspirin seems to be one option.  Persantin or coumadin also thin the blood and help it get past arteriosclerosis (hardening of the arteries) and atherosclerosis, where fatty deposits block blood flow.  Controlling your blood pressure and blood sugar also helps.

P:  You don't mention ginkgo biloba, and several other doctors in this forum have said that there's very little or no empirical evidence that it helps ocular blood flow.  Yet I've seen papers --most notably a very positive one by Dr. Robert Ritch -- that suggest otherwise.  What's your take on ginkgo?  (Sorry everybody, I know I ask this question frequently, but I'm looking for a consensus.)

Dr. Rick Wilson:  Dr. Ritch is high on ginkgo, but most of us feel there are not enough good studies that prove the benefits of ginkgo on circulation are worth the possible side effects of inconsistent strength in an over-the-counter herbal medicine.

P:  Does head position affect the blood flow to the eye?

Dr. Rick Wilson:  Absolutely.  When we are standing, most of our blood falls to our feet and needs to be pushed up strongly by the venous return.  When we lie down, our venous blood pressure rises, which causes the IOP to rise on a one-to-one basis.  Clearly, if the head is down and the feet are up, the opposite of standing up happens, and the eye pressure of someone normal will rise to the mid-30s.

Moderator:  Can you give us a quick update on the World Glaucoma Congress in Vienna, from which you just returned?

Dr. Rick Wilson:  We had representatives from 62 glaucoma societies.  It was neat to meet people that I have been e-mailing and give the name a face.  No real new news, however.

Moderator:  Thank you, Dr. Wilson.

On July 20, Dr. Werner discussed "Glaucoma and Stress" in the Chat room. Click here for highlights of that meeting.

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