Normal-Tension Glaucoma And The Family Connection
Chat Highlights
May 5, 2004

Norma Devine, Editor

On Wednesday, May 5, 2004, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Normal-Tension Glaucoma And The Family Connection."

Moderator:  Tonight's topic is "Normal-Tension Glaucoma And The Family Connection."  

P:  What does "normal-tension" mean? 

Dr. Rick Wilson:  The "normal" refers to the intraocular pressure (IOP).  Therefore, it means that the glaucoma damage is happening at a normal IOP.   

P:  Wouldn't it be easy to overlook normal-tension glaucoma (NTG) if the IOP is normal?

Dr. Rick Wilson:  The doctor would, of course, have to look at the optic nerve to diagnose the condition.  It is usually not a subtle sign.

P:  What are the odds of passing NTG down from one generation to the next?  Is it the same as with other types of glaucoma?

Dr. Rick Wilson:  I cannot remember any articles about that.  If you have a mother, father, sister, or brother who has glaucoma, then your chances of having glaucoma are 10 to 15 times greater than average. That is also the case for primary open-angle glaucoma (POAG).  Low-tension (or normal-tension) glaucoma accounts for one out of every six open-angle glaucoma cases in the United States.

Moderator:  Is the risk for having a family member with glaucoma the same in Japan, where NTG rates are high, as in North America?

Dr. Rick Wilson:  I would think in general, yes.  But I don't know the actual numbers.  Our best numbers for family history come from the Rotterdam study.

P:  What was that study about?  

Dr. Rick Wilson:  It was a population-based study like the Baltimore eye study.  It was looking for the prevalence of eye disease in the population.

P:  I was treated in Florida in 1993 for NTG.  Both of my siblings were tested and were okay at that time.  Now they both have NTG.  Is there a chance that my children will get  NTG?

Dr. Rick Wilson:  Yes, there is definitely a greater chance that your children will get NTG, but the chances are probably less than 30%. 

P:  My mother went blind from NTG.  Can I expect the same the result?   

Dr. Rick Wilson:  The severity of a parent's glaucoma can serve as an indication of how difficult your glaucoma will be to control.  You will have much better medical care than your mother did.  I certainly do not think you will have the same result.

P:  What does glaucoma damage mean?

Dr. Rick Wilson:  Glaucoma damage is the injury done to the retina and the optic nerve by elevated pressure in primary open-angle glaucoma (POAG), and by other factors in NTG. 

P:  What are the "other factors" besides vascular?  

Dr. Rick Wilson:  It appears at this time that vascular factors, which include low blood pressure at all times or just during the night, and vasospastic diseases, like migraines and Raynaud's, are the chief known risk factors for NTG.  Other factors include autoimmune disease, cardiovascular disease, and abnormal blood thickness or clotting.

P:  My mother was diagnosed with NTG when she was 82-years old.  Would you say that this is a kind of "geriatric glaucoma" that doesn't have the same genetic bearing on relatives that glaucoma developing at an earlier age might have?

Dr. Rick Wilson:  Yes, I would say that.  Normal-tension glaucoma is usually seen in older patients.  If I see a patient in his or her early fifties with NTG, that patient is almost always female and has low systemic blood pressure.

P:  What is considered low blood pressure?

Dr. Rick Wilson:  I consider low blood pressure to be 90 over 50 mm Hg and below.

P:  Shouldn't a blood pressure check be part of a regular glaucoma exam?

Dr. Rick Wilson:  The ophthalmologist should be asking patients about their last physical exam.  I only check blood pressure if I am acutely concerned about the patient or the blood pressure has been very volatile.

P:  When you see patients under 50 years of age, male or female, who have been diagnosed with NTG, what then?

Dr. Rick Wilson:  I would first check their corneas to make sure that they were not thinner than normal and therefore giving me a lower than actual IOP.  I would also check a diurnal curve of eye pressure to make sure I wasn't missing a pressure spike.  Since my strong hunch would be that they have a problem with circulation, I would investigate that by checking their blood pressure and doing blood tests in conjunction with their internist.  If their blood pressure was normal during the day, I might want to do a 24-hour blood pressure monitoring.

P:  How are IOP and blood pressure measured for a 24-hour period?  I have no way to measure my IOP at home.  How often is the blood pressure measured during that 24-hour period?  

Dr. Rick Wilson:  We don't have a good way to check IOP at home.  We do have 24-hour blood pressure monitors that check the blood pressure as often as desired. The readings are recorded and can be reviewed later.

P:  What is the most effective treatment for NTG?

Dr. Rick Wilson:  The only proven treatment for any of the glaucomas is to lower IOP by 30 to 40%, or to get the IOP down to what you think is a safe range.

P:  What success have you had in lowering IOP in NTG patients to below 10 mm Hg with medications and laser surgery alone?

Dr. Rick Wilson:  Modest success.  Most of the time, surgery will be needed to get the IOP down to less than 10 mm Hg.

P:  What research, if any, is being done to understand the cause(s) of NTG?  

Dr. Rick Wilson:  Dr. Marty Wax has been working to discover the relationship between autoimmune disease in NTG.  He has identified the antigen that antibodies are made against in these patients.  Many other doctors are looking into how circulation can cause damage to the optic nerve.  Our understanding is moving forward fairly rapidly from my standpoint but slowly, I am sure, from yours.

P:  I was diagnosed with NTG when I was 42-years old.  I had surgery (trabeculectomy) in Florida.  Do you see trabeculectomies that last more than 10 years and do not need to be repeated?  Is it true that trabeculectomies last longer in fair-skinned people? 

Dr. Rick Wilson:  The answer to both questions is yes.  

P:  I am 61-years old, recently diagnosed with NTG.  My doctor has tried Betoptic S, Alphagan, Xalatan and Lumigan, each alone.  My target IOP has been set for 10 to 12 mm Hg., but I have not been able to reach it.  Now I'm on Betoptic S in the morning and  Xalatan at night, one drop each.  If I don't reach the target, my doctor wants to do laser surgery.  I've only been treated for two months.  Should I get a second opinion before agreeing to the laser surgery?  I could not tolerate Lumigan or Alphagan.

Dr. Rick Wilson:  Betoptic S is a 12-hour drop, so using it once a day does not make sense to me.  I would certainly be using it twice a day, and waiting 10 minutes between the Betoptic and the Xalatan in the evening.  If you cannot use Alphagan, have you tried Azopt, Trusopt, or Cosopt?  One of these drugs might help, before you try laser surgery (trabeculoplasty).  

P:  According to that,  I guess I've wasted three weeks of treatment.  Should I call my glaucoma specialist and suggest trying the new treatment you mentioned?  I don't know how to handle this.  This is my last chance, the doctors said, before having laser surgery.  I'd like to try something else first, unless laser surgery is necessary.  I take Ziac for high blood pressure.  Would using the Betoptic S be too much two times a day?  

Dr. Rick Wilson:  Are you seeing a glaucoma specialist? Does he or she see only glaucoma patients?  You could see a second glaucoma specialist and choose the one that communicated best with you.

P:  Which glaucoma drops are more harmful to the cornea?

Dr. Rick Wilson:  Xalatan, Travatan, and Lumigan can cause toxic reactions to the cornea -- mainly non-healing deficits in the top layer of the cornea. The beta blockers can anesthetize the cornea, and Trusopt and Azopt can cause mild corneal swelling in patients with already sick corneas.

P:  Do you ever recommend good docs in the San Francisco area?  

Dr. Rick Wilson:  There are many good glaucoma people there.  Look on the American Glaucoma Society website for a specialist near you.  The website is www.glaucomaweb.org or www.americanglaucomasociety.org.

Moderator:  Thank you, Doctor Rick, for your help.

Dr. Rick Wilson:  I'm falling asleep in my chair, so will say good night.  See you in a week.

End of highlights for May 5, 2004.

On May 12, Dr. Wilson discussed "Ocular Emergencies" in the Chat room. Click here for highlights of that meeting.

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