Chat Highlights
Open-angle Glaucoma
August 22, 2001

Norma Devine, Editor

On Wednesday, August 22, 2001, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Open-angle Glaucoma." 

Moderator:  The topic tonight is "Open-angle Glaucoma."  Dr. Rick, is that the most common kind of glaucoma? 

Dr. Rick Wilson:  Yes, it is the most common type of glaucoma in the U.S., Canada, and Europe.  In Japan, normal-tension glaucoma is the most common, as is angle-closure glaucoma in China.  In our population, about 85% of glaucomas are open-angle, either primary (no underlying cause) or secondary (secondary to inflammation), previous trauma, pseudoexfoliation, etc.

P:  Do all normal-tension (NTG) patients have open-angle glaucoma?

Dr. Rick Wilson:  Yes, they do.

P:  So, we want our angles open, and not closed?  Is that right? 

P:  I'll take my angles open, thank you.

Dr. Rick Wilson:  It is better to have angle-closure glaucoma if it is acute, because treatment (peripheral iridectomy) can cure it, whereas open-angle glaucoma is usually chronic.

P:  Are there any provocation tests to see if a patient's open angle remains open under different conditions?

Dr. Rick Wilson:  Yes, but none of them are physiologic (i.e., seen under normal conditions) and are not very helpful in determining who has the propensity to develop angle closure.

P:  Just about every medication has warnings about use if you have glaucoma.

Dr. Rick Wilson:  Those warnings apply only to those patients with narrow and occludable angles.  Topical or oral steroids are the only medication that patients with open-angle glaucoma need to be fearful of.   

P:  I have open-angle glaucoma.  This year I asked my internist for a steroid shot because of being very run down at a time I needed to have lots of energy.  Was I wrong to ask for a steroid shot?   

Dr. Rick Wilson:  A short run of oral steroids should not raise your IOP for long.   Longer doses are more dangerous.

P:  For how long does a steroid injection affect the body, e.g., the IOP? 

Dr. Rick Wilson:  It depends upon the kind of steroid.  Some last two to three days; others can last up to six weeks or much longer.  

P:  What effect, if any, do cortisone injections have on open-angle glaucoma patients?

Dr. Rick Wilson:  They have the potential to raise intraocular pressure in susceptible (steroid responders) patients. About 95% of patients with primary open-angle glaucoma are steroid responders.

P:  Could you explain steroid responders?  

Dr. Rick Wilson:  Sixty-five percent of the population, when given dexamethasone (a strong steroid) for six weeks, will have an IOP rise of 5 mm HG or less.  Five percent will get an exaggerated rise in pressure of 15 mm HG or more, and the rest will be in the 6 to 14 mm range.

P:  In closed-angle glaucoma, miotics such as pilocarpine are used to open the angle, but by what mechanism do they reduce intraocular pressure in open-angle glaucoma?  

Dr. Rick Wilson:  By constricting the pupil, pilocarpine causes the iris to be pulled away from the wall of the eye.  Since the iris inserts at the back of the trabecular meshwork, pulling on the iris mechanically opens the trabecular meshwork and improves the flow of aqueous through it.

P:  If you are on drops for open-angle glaucoma,  you will probably be on them for life.  It's not like elevated blood pressure where, with exercise and weight loss, you might be able to stop using medications.  That's not true for open-angle glaucoma.  It's just something you learn to live with.

Dr. Rick Wilson:  Yes, although weight loss and exercise can lessen your need for eye drops.

P:  I am 21 years old, my IOP ranges between 26 and 30 mm Hg, and my c/d (cup-to-disk) ratio is 4/7.  Do I have glaucoma? 

Dr. Rick Wilson:  I don't know whether the c/d 0.4 refers  to the right eye and the 0.7 to the left  eye, or whether the first number relates to the horizontal cup diameter and the second number relates to the vertical.  I would have to say that IOPs of  26 to 30 mm Hg are high for any age, but very high at age 21.  Do you have a family history of glaucoma?

P:  None of my family members have glaucoma, but an uncle who is very old uses glaucoma medications.  My older brother is fine.  I wanted to know whether my case could be ocular hypertension, because I don't have any loss of visual field. 

Dr. Rick Wilson:  Without seeing you, I can't say.  I would expect you to have damage, or develop it over the next year or so, and would probably treat you with meds.

P:  So you can't say whether I  have glaucoma or ocular hypertension.   I hear that many people have high pressures and don't develop any damage.

Dr. Rick Wilson:  Did the doctor see glaucoma damage in your disc?  Did you see a glaucoma specialist?  The stakes are too high for you not to.

P:  What does glaucoma damage mean?  The doctor just said that I have "cupping" and that my (optic) nerves look pretty good.  Could you please tell me what having a damaged disc means? 

Dr. Rick Wilson:  Damage is injury to the optic nerve that adds up over time to visual field loss.  Visual field loss is a late sign of glaucoma.  Thirty to forty percent of the optic nerves are lost by the time visual field loss is seen.  That is why you need to be seeing someone who can pick up early glaucoma by the appearance of the optic nerve tissue, and not the size of the cup.

Moderator:  Would you explain more about cupping?

Dr. Rick Wilson:  Most people have a depression in the middle of the optic nerve that is called the cup.  Often patients with near-sightedness have big eyes and a big canal in the back of the eye for the optic nerve to pass through.  A far-sighted person will have a small eye, small canal and the same amount of nerve tissue.  Injury to the optic nerve causes it to shrink away and leaves a bigger depression, or cup, indicative of glaucoma damage.

P:  I'm 36 years old, have pigment dispersion syndrome, and just had a trabeculectomy on my left eye.  My pressure was running between the high 20's to the low 30's on Cosopt, Alphagan, and Xalatan.  I read that the trab is likely to last only about seven years.  Is it likely there might be other treatments coming out so I won't have to undergo another trabeculectomy?  

Dr. Rick Wilson:  Yes, I would expect better medicines and better surgery by the end of seven years.  Besides, seven years is an old figure.  Surgery has been improving steadily, so we don't know how long the present surgery will last, on average.  

P:  Last week my glaucoma specialist said I have folds in the cornea of the eye that had a trabeculectomy.  The IOP in that eye is 2.5 mm Hg,  It has been down to 0 mm Hg, but  never higher than 4 mm Hg during the past four years.  My remaining vision in that eye

(lower half) is not blurred, and the doctor is taking a wait-and-see approach.  Is this a condition that might resolve itself?  Would you proceed differently?

Dr. Rick Wilson:  If the eye is quiet and there is no reason to think that more scarring will occur and if your vision is unacceptably blurred, it might be time to consider a flap revision or blood injection.  It's hard to tell without a good history and look at you. 

P:  Can a flap revision or a blood injection ever make your vision worse?

Dr. Rick Wilson:  If the sutures are too tight, you can get large amounts of astigmatism that glasses may not correct for.  

P:  I am about to start taking a calcium channel blocker for hypertension (130/95) as prescribed by my internist.  How might that affect my glaucoma?

Dr. Rick Wilson:  If you have any vasospasm, as is common in patients with normal-tension glaucoma, it could help you.  If you have low blood pressure, especially from 2:00 to 4:00 a.m., it could drop your blood pressure lower and hurt you.

Moderator:  Thanks, Dr. Rick.  You've had a long day.  Hope you get a good night's sleep.

Dr. Rick Wilson:  Thanks for the good wishes.  Yes, bed looks very good now.  Have a great week.

End of highlights for August 22, 2001.

On August 29, Dr. Werner discussed "Normal-tension Glaucoma" in the Chat room. Click here for highlights of that meeting.

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