Neurology and Glaucoma
Chat Highlights
November 5, 2003

Norma Devine, Editor

On Wednesday, November 5, 2003, Dr. Mark Moster, a neuro-ophthalmologist at Wills, and the glaucoma chat group discussed "Neurology and Glaucoma."

Moderator:  Welcome, Dr. Moster.   Thank you for agreeing to join us in the chat room to discuss neurology and glaucoma.  

P:  Two of my friends from the brain tumor message board are here tonight.  Their tumors have nothing to do with glaucoma, but having a neuro-ophthalmologist to answer their questions is valuable to them.

Moderator:  Dr. Moster, what is a neuro-ophthalmologist?

Dr. Mark Moster:  A neuro-ophthalmologist is either a neurologist, or an ophthalmologist with extra training in the field.  We deal with eye manifestations of neurologic conditions.

Moderator:  Where did you receive your training? 

Dr. Mark Moster:  I did my residency in neurology at the University of Pittsburgh, and my fellowship in neuro-ophthalmology at Wills Eye Hospital.

P:  Under what circumstances would a glaucoma patient be referred to a neuro-ophthalmologist?

Dr. Mark Moster:  Usually, when the ophthalmologist is considering that there may be a cause for visual loss other than glaucoma. There may be two causes for the visual loss, or there may be another problem mimicking glaucoma.

P:  What testing do neuro-ophthalmologists perform that  ophthalmologists may not have access to or know of?

Dr. Mark Moster:  Our examination is more focused on neurologic conditions.  Besides an eye examination, we do a neurological examination.  We also put more emphasis on certain aspects of the eye examination that suggest neurologic disease.

P:  I have seen two neuro-ophthalmologists for chronic eye pain and neither one of them did a neurologic exam.  (I have a strong family history of myotonic dystrophy.)  They just examined my eyes.  Does the type of examination a patient gets vary according to the neuro-ophthalmologist's training? 

Dr. Mark Moster:  The amount of a neurological exam depends somewhat on the doctor's background , but also on the symptoms. Much of the neurological exam consists of examining the cranial nerves, which are near the eyes.

P:  You mentioned that the neurological examination includes examination of the cranial nerves.  Can you tell us how that is done? I was referred to an optic nerve specialist by my ophthalmologist, but I don't recall his doing anything different during his exam.

Dr. Mark Moster:  There are 12 cranial nerves:  (1) sense of smell; (2) vision; (3, 4, 6) move the eyes; (5) sensation around the eye and face; (7) checked by looking at facial muscles; (8) hearing and balance (look for nystagmus, too); (9, 10) movements of the pharynx; ( 11) shoulder and neck movement; (12) tongue movement. That is a quick run- through.

P:  I saw a neuro-ophthalmologist and had the Golden Globe test to find my loss of peripheral visual field.   

Dr. Mark Moster:  I think Golden Globe is a national award.  I don't know of a golden globe test.

P:  Do neuro-ophthalmologists' visual field tests differ from those administered for glaucoma? 

Dr. Mark Moster:  We use the same visual field tests for the most part:  the central threshold type tests on the Humphrey or Octopus machines.  We tend to use the Goldmann visual field test (done by a technician, not with a computer) a little more often in neurology.  Maybe that is the test the patient called the Golden Globe test.

P:  Yes, I may have used the wrong name of the test.  The doctor looked through the center of a large, concave dish to make sure of where I was looking, and then I responded to a series of large and small dots.  

Dr. Mark Moster:  That sounds like a Goldmann visual field test.  It is different from the computerized tests in that the lights are moved in from the periphery towards the center, instead of just flashing on and off.

P:  How can you tell whether optic nerve damage is caused by high pressure or a neurological disorder?

Dr. Mark Moster:  That's often hard to tell.  However, there are often differences in the history and examination that help make that distinction.  For instance, the visual fields may have different characteristics, and the appearance of the optic nerve also has differences.  With neurological disorders, the visual loss may be sudden or progress more rapidly.  There may be headache or other neurological symptoms.

P:  Because glaucoma is defined as damage to the optic nerve, is glaucoma considered a neurological disease? 

Dr. Mark Moster:  Most would not consider it a neurologic disease, because the likely cause is elevated intraocular pressure.  The damage, however, is to the optic nerve, which is part of the brain, so I would consider glaucoma a neurological problem.  It is the most common cause of optic nerve damage that we see.

P:  Can a trabeculectomy lead to chronic eye migraine?

Dr. Mark Moster:  Trabeculectomy does not specifically lead to migraines.  People with migraine, however, may be very sensitive to any stimulus around the face or eye.  In these cases, migraine may occur.  It would, however, be very unusual to be chronic.  

P:  Is there any relationship between elevated intraocular pressure and migraines?

Dr. Mark Moster:  We know that patients with normal-tension glaucoma have migraines more frequently than in the rest of the population, and more frequently than patients with the higher pressure variety of glaucoma.  High pressure in the eye can cause eye or head pain, but not, as a rule, until the pressure gets very high.  

P:  Is there any relationship between nystagmus and glaucoma? How are people with nystagmus best followed for glaucoma damage?

Dr. Mark Moster:  There is no direct relationship between the two.  However, visual loss from any cause can result in nystagmus, and that can occur in glaucoma.  You would ask a glaucoma specialist about following nystagmus patients, but my thoughts are that you look at visual fields and the optic nerve as in patients without nystagmus.

P:  I was just wondering how accurate visual field tests can be in a patient with nystagmus.  Nystagmus causes me to unintentionally "cheat," so the computer has been unable to plot my blind spot.

Dr. Mark Moster:  It may be less accurate than if there were no nystagmus, but I still think it is worthwhile.  Just because the computer doesn't plot the blind spot doesn't make it invalid.

P:  What is the significance of optic nerve pallor?

Dr. Mark Moster:  The optic nerve normally has a pink/orange color. When it turns more white, we call it pallor.  In glaucoma patients, there is pallor within the cup that is enlarging. The surrounding rim, however, usually maintains its normal color.  In neurologic diseases affecting the optic nerve, the rim becomes pale. This is one of the clues to us for further neurologic testing.

P:  It seems to me that saying the optic nerve is turning "more white" is a subjective judgment.  How does a doctor decide that the nerve is, say, 40% damaged? 

Dr. Mark Moster:  Yes, it is subjective.  However, we have clues. Often one nerve is more pale than the other, or more pale in one part of the nerve than another. When we start out, there is usually a similar color throughout the nerve tissue.  As to 40% damage, that could be estimated by nerve appearance, visual field, or other visual parameters.

P:  About two weeks after having maxillofacial surgery for an impacted wisdom tooth and a bone graft on the jaw (left side), I noticed a blind spot in my right eye.  As I am an artist and use my eyes critically, I am certain that the scotoma was sudden.  My angles are wide open, pressures were, and still are, normal.  I was told the optic nerve rim was pale.  Is it possible that something in the general anesthesia I was given could have caused this damage? If so, what might it be?  What treatment or precautions should I take to avoid further damage?

Dr. Mark Moster:  That is a very difficult question to comment on. I would have to examine you carefully.

P:  Would you say it's possible to be susceptible to a neurological disorder without showing evidence of it?  That is, to need some external factor, say something chemical or accidental, to bring on the problem in full force?

Dr. Mark Moster:  I'm not sure exactly what you're asking, but I'll try to answer.  I think many people are born with a genetic predisposition to a disease.  Only some of them, however, develop the disease.  Those with the disease may have been exposed to something in the environment, such as a virus, that triggered the disease to become apparent.

P:  I guess everything the body does or doesn't do correctly can be traced back to the brain, since it controls everything.  For instance, if poor blood flow or perfusion is what caused the glaucoma, doesn't circulation get traced back to the brain not giving the proper signals?

Dr. Mark Moster:  I think there are many possibilities for decreased blood flow in various body regions. There could be atherosclerosis, blood loss, spasm caused by other stimuli, etc. It could be lack of brain control sometimes, but I'm sure there are many other possibilities.

P:  If an ophthalmologist orders an MRI (magnetic resonance imaging) of the eye orbits and brain, would he or she know what to look for in the brain portion of the MRI?  I feel more confident that a neuro-ophthalmologist would know.  What do you think?

Dr. Mark Moster:  The MRI is interpreted by a radiologist, whose job it is to be able to interpret the study.  The ophthalmologist will generally rely on the radiologist's expertise.

P:  I have amblyopia and it's very hard to describe to someone how I see.  It's like there's a short circuit between my eye and brain.  Is amblyopia considered a neurological problem? 

Dr. Mark Moster:  I would certainly consider it a neurological problem, because the brain is not seeing what is coming in from that eye in a normal fashion.

P:  I've had two orbital blocks to dampen my nystagmus, so my glaucoma doc could get a good look at my optic nerve and do an HRT (Heidelberg retinal tomography) and OCT (optical coherence tomography).  He uses lidocaine and a needle under my eye (although last time it failed, and he did it around my eye).  Where is that needle going when he blocks CN 2, 3, 4, 5.3, and 6?  The cavernous sinus?  (By the way, I'm a second-year pediatric resident.) 

Dr. Mark Moster:  The block is retrobulbar, right behind the eye. It should not reach the cavernous sinus.  Another option for examining the nerve is under general anesthesia, but you wouldn't be able to do the HRT or OCT.

P:  Do you think it will be possible to re-grow or reproduce nerve cells, or is that wishful thinking?  

Dr. Mark Moster:  My educated guess is that it is possible within 10 to 20 years.  

P:  If amblyopia involves the brain not properly interpreting the signals it receives, when you get an intraocular lens after a cataract operation in an amblyopic eye, can it take some time before the brain responds to the new input?

Dr. Mark Moster:  I think the improvement is less, in that you don't likely get to 20/20.  I don't, however, think it takes longer to see the improvement.

P:  When I'm not using glaucoma eye drops, my vision has an area in the center that flickers when I wake up in the morning, and stops after a few minutes.  Would that be neurological?

Dr. Mark Moster:  That does not sound like a typical neurological symptom.  I wonder if it is related to pressure, since it occurs off the drops.

P:  What type of intervention is a neuro-ophthalmologist able to provide when damage to the optic nerve is due to neurological causes?  

Dr. Mark Moster:  That depends on the cause.  Many different processes affect the optic nerve, including tumors, multiple sclerosis, strokes, infections, etc.  The intervention depends on the cause.

P:  Do you ever deal with tumors on optic nerves?  If so, and they are operable, do you operate, or does a neurosurgeon, or do you ever team up with a neurosurgeon?

Dr. Mark Moster:  Neurosurgeons operate on the optic nerve if the tumor is in the brain,  but some ophthalmologists are trained as orbital surgeons and operate on the optic nerve behind the eye in the orbit.  I, as a neurologist, don't personally operate.

P:  Are you familiar with the memantine study at Wills?  I'm participating in the study, and never asked what makes researchers think memantine might work for glaucoma.  Memantine was approved by the FDA to treat patients with advanced Alzheimer's disease.  

Dr. Mark Moster:  Well, memantine blocks the NMDA (N-methyl-D-aspartate) receptors, which, when activated, allow calcium into the cell and cause damage.  That is felt to be the cause of degeneration of nerve cells.  It's actually quite complicated.  Memantine, by blocking the glutamate-activated NMDA receptors, may protect the nerve cells.  

Moderator:  Thank you, Dr. Moster.  You did a great job.  We  really appreciate your joining us.

Dr. Mark Moster:  Good night all, and thank you for the interesting questions.

End of highlights for November 5, 2003.

On November 12, Dr. Wilson discussed "Combined Mechanism Glaucoma" in the Chat room. Click here for highlights of that meeting.

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