Glaucoma Risk Factors and Their Significance
Chat Highlights
June 25, 2003

Norma Devine, Editor

On Wednesday, June 25, 2003, Dr. Elliot Werner, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Glaucoma Risk Factors and Their Significance."

Moderator:  Welcome back, Dr. Werner.  Let's begin by discussing some of the 17 risk factors listed on this web site at http://www.willsglaucoma.org/risks.html. 

Dr. Elliot Werner:  First, let me define risk factor.  A risk factor is something you have that increases the chance you will develop a certain disease beyond that of the average population. It doesn't mean you have or will get the disease.  It just means that your chance is greater than average.

Moderator:  What are the risk factors for open-angle glaucoma?

Dr. Elliot Werner:  There are five well-recognized risk factors for open-angle glaucoma:  intraocular pressure (IOP), age, myopia, race, and family history.

Moderator:  What is the significance of elevated IOP?

Dr. Elliot Werner:  The higher the IOP, the greater the risk.  If you have an IOP over 21 mm Hg or so, the risk of developing glaucoma is about 9 to 10%.

Moderator:  Do different types of glaucoma have different risk factors?

Dr. Elliot Werner:  Right.  For example, hyperopia (farsightedness) is a risk factor for angle-closure glaucoma.  Diabetes is a risk factor for neovascular glaucoma.  Trauma is a risk factor for angle-recession glaucoma, and so on.  

Moderator:  How important is a family history of glaucoma?  

Dr. Elliot Werner:  A strong family history of glaucoma -- meaning a first-degree relative -- increases your risk by about twice.  Roughly doubles the risk, in other words.

Moderator:  Does angle-recession glaucoma mean the angles are closed?

Dr. Elliot Werner:  No. In angle recession, the angles are open, but torn by an injury.

Moderator:  In unilateral glaucoma, does the other eye always become glaucomatous?

Dr. Elliot Werner:  In the more common open- and closed-angle types, yes.  In other types, depending on the underlying cause, unilateral glaucoma may be the rule.  For example, traumatic glaucoma is unusual in both eyes.

Moderator:  What types of eye injury are risk factors for glaucoma?  

Dr. Elliot Werner:  Blunt trauma is more risky for glaucoma.  It usually is fairly severe and often associated with hyphema -- bleeding into the anterior chamber. The most common causes are fists and balls and hockey pucks.

Moderator:  What does "blood thickening" mean, and why is that a risk factor? 

Dr. Elliot Werner:  I'm not sure. Blood thickening is not a precise term, and I am not sure what you are referring to.

Moderator:  It is one of the 17 risk factors listed on this web site.   Next question:  How important is nearsightedness in determining the risk of glaucoma?

Dr. Elliot Werner:  In higher degrees of myopia -- 5 diopters or more -- the risk of open-angle glaucoma is increased about 2 to 3 times. Contrast that with elevated IOP, where the risk is increased about 5 to 10 times.

Moderator:  Why is retinal detachment a risk factor? 

Dr. Elliot Werner:  Patients who have had surgery for retinal detachment are more prone to angle-closure and inflammatory glaucomas due to the scleral buckle placed in the surgery.  They are often myopes, or have had previous eye surgery or trauma, which can also increase the risk of secondary glaucomas.

P:  Do some risk factors compound?  For instance, does the chance of developing glaucoma from trauma increase with myopia?  

Dr. Elliot Werner:  Generally, the risk factors add up.

Moderator:  Why are narrow angles a risk factor? 

Dr. Elliot Werner:  Narrow angles are a risk factor for angle-closure glaucoma.  People with critically narrow angles have a lifetime risk of about 30% of developing angle closure.

P:  This question is from a patient who could not be here tonight.  He suffered a slight concussion at age 8.  He was diagnosed as a glaucoma suspect at age 22.  At age 29, his diagnosis was normal-tension glaucoma. His IOPs are now 16 and 20 mm Hg.  There is no family history of glaucoma.  Could the concussion years ago have caused his glaucoma?

Dr. Elliot Werner:  Close head trauma can cause optic nerve damage that resembles normal-tension glaucoma (NTG), but does not usually progress.  A concussion itself is not a risk factor for NTG. If he has progressive changes, then it is more likely glaucoma.  

P:  Isn't NTG rare in such a young person?  

Dr. Elliot Werner:  Yes, NTG is unusual in patients that young.

P:  Why is an unhealthy optic nerve a risk factor for glaucoma? Is that the most important risk factor?  Does an unhealthy optic nerve always mean a damaged optic nerve?

Dr. Elliot Werner:  That depends on what you mean by "unhealthy."   A damaged optic nerve is not a risk factor, because if the nerve is damaged you already have the disease.  Remember, a risk factor increases the chance that a currently healthy individual will become sick later on.

P:  I developed a scotoma in one eye following maxillofacial surgery, and I have reason to think that something in the general anesthetic mix, or lack of oxygen, or perhaps body position during the surgery, caused the scotoma.  When I spoke to the doctor about my suspicions, he said, “Could be.”  As I recall, I thoughtlessly signed a waiver that mentioned blindness as a possible outcome prior to surgery.  Would you please comment on anesthesia, or surgery in general, as risk factors for eye damage, and can you tell us what precautions we might take if we have to have surgery.

Dr. Elliot Werner:  It's hard to diagnose exactly what happened without examining you.  One possibility is a drop in blood pressure under anesthesia, resulting in reduced blood supply to the optic nerve for a period of time, producing what is called ischemic optic neuropathy.

P:  Please discuss the risk factors for pigmentary dispersion syndrome, pseudoexfoliation, and corneal endothelial dystrophy. 

Dr. Elliot Werner:  Pigment dispersion is a risk factor for developing pigmentary glaucoma. 

Pseudoexfoliation is a risk factor for developing exfoliative glaucoma.  Corneal endothelial dystrophy is controversial. The evidence that it is a risk factor for glaucoma is not very strong.  

P:  Please discuss the pigment-dispersion syndrome.

Dr. Elliot Werner:  In that condition, pigment from the back surface of the iris is shed into the aqueous fluid and floats around the anterior chamber.  It produces characteristic findings in the cornea, iris and angle that can be seen with a slit lamp. Somewhere between 10 and 50% of patients with pigment-dispersion syndrome develop pigmentary glaucoma. 

Moderator:  How about pseudoexfoliation glaucoma?

Dr. Elliot Werner:  Pseudoexfoliation is a degenerative condition affecting the structures in the anterior portion of the eye.  Abnormal protein-like material is deposited on the lens, iris, cornea, and angle. Again, these changes can be seen with the slit lamp.  About 25 to 50% of patients with pseudoexfoliation will develop exfoliative glaucoma. 

Moderator:  What is Fuch's dystrophy and does it usually lead to glaucoma?

Dr. Elliot Werner:  Corneal endothelial dystrophy, or Fuchs' dystrophy, is a degenerative condition affecting the cells that line the back surface of the cornea.  As these cells die and cease to function, the cornea becomes swollen and cloudy.  The only effective treatment is corneal transplant.  There is some evidence that the occurrence of glaucoma is more common in these patients, but the studies are weak and not everyone believes that is true.

P:  What role does race play?  

Dr. Elliot Werner:  The prevalence of open-angle glaucoma is about 4 to 8 times more common in African-derived populations than in European-derived populations.  Normal-tension glaucoma is more common in Asians.  Angle-closure glaucoma is also more common in Asians, and is especially common in Eskimos.

P:  What would be the chances of a person with Graves' eye disease -- who has had ocular-decompression surgery, and whose IOP's continue to be high -- developing glaucoma?

Dr. Elliot Werner:  That depends upon why the IOP is elevated.  It is possible the person simply has ocular hypertension unrelated to Graves'.  In that case, the general risk is about 9 to 10%.

P:  Is central corneal thickness a true risk factor, that is, apart from its confounding effect on IOP measurement?  In other words, do thinner corneas at a given IOP pose a greater risk of progressing to nerve damage than thicker corneas at the same actual IOP?

Dr. Elliot Werner:  Corneal thickness is a risk factor for developing glaucoma in ocular hypertensives.  That stands apart from any consideration of IOP.  Corneal thickness has not been shown to be a risk factor in the normal population.

P:  Is race still a risk factor when the cornea thickness of African- Americans is not a consideration?  

Dr. Elliot Werner:  The multivariate analysis seemed to show that. However, when the cup-to-disc ratio was taken into consideration, as well as the corneal thickness, race was no longer a risk factor. 

P:  I have ICE (iridio-corneal syndrome), which caused closed-angle glaucoma. I am also myopic. Does that put me at risk for open-angle glaucoma?  Is it possible to have mixed-mechanism glaucoma?

Dr. Elliot Werner:  Once your angle closes from ICE syndrome, you cannot, by definition, develop open-angle glaucoma.  Personally, I do not believe there is any such condition as mixed-mechanism glaucoma.

P:  How does one ensure, or help to ensure, that blood pressure won't plummet during a surgical procedure, so that surgery is less of a risk factor for glaucoma?

Dr. Elliot Werner:  Who do you mean by "one?"  The patient cannot do anything to ensure that.  That is up to the anesthesiologist.  A drop in blood pressure (hypotension) is a recognized risk factor of general anesthesia and sometimes simply cannot be avoided. 

P:  How much is now known about genes as risk factors, and are there any populations in which glaucoma (of all types) is remarkably low?

Dr. Elliot Werner:  I don't know and I have not read anything like that, but I have heard that glaucoma is rare among Australian aborigines

P:  Are migraine headaches or ocular migraines a risk factor? 

Dr. Elliot Werner:  That's another controversial area.  Most population studies have not found migraine to be a risk factor.  There is some weak evidence that it may be a risk factor for normal-tension glaucoma, but not an important one.

P:  Nocturnal systemic hypotension (low blood pressure during sleep) is often cited as a suspected risk factor, but how is its presence demonstrated clinically? 

Dr. Elliot Werner:  That generally requires admission to a sleep center to monitor blood pressure during sleep. There is, again, some weak evidence that it may be a risk factor, but so far no population studies show that. 

P:  What is the risk of an epidural steroid injection (80 mg, methylprednisone) in an early POAG patient (possibly exfoliative), who seems to be a strong steroid responder, even by POAG standards. How long might the effect of such a single injection last? 

Dr. Elliot Werner:  Methylpred is pretty short-acting.  One dose is not likely to have much effect on the eye.  Most exfoliative glaucoma patients, in fact, are not steroid responders, so that is unusual.

P:  I'm wondering about the listed risk factor (http://www.willsglaucoma.org/risk.html) concerning "last medical eye exam."  For example, in the past 2 years (0 points); 2 - 5 years ago (1 point); more than 5 years (2 points).  I would think an eye exam would catch glaucoma early, but don't see how the risk factor can increase if you don't have regular exams. Please explain.

Dr. Elliot Werner:  The point is that a risk factor is something you have that is associated with a statistically increased risk.  A risk factor is not a cause; it's just an association.  There is an association between not having had an eye exam recently and developing glaucoma.

Moderator:  Why are abnormal visual field tests a risk factor?  How can you tell if the defect is from glaucoma or some other cause?  

Dr. Elliot Werner:  An abnormal visual field is not a risk factor.  If the visual field is abnormal, you already have the disease.  Remember, a risk factor is found in a healthy person who does not have the disease at present.

Moderator:  Why is diabetes a risk factor?  

Dr. Elliot Werner:  Most recent population studies have not found diabetes to be a risk factor for open-angle glaucoma.

Moderator:  The risk-factor page on this site says diabetes increases the risk two times.

Dr. Elliot Werner:  I disagree with that part, as does most of the medical literature.  Diabetes, or more correctly, diabetic retinopathy, is a risk factor for developing neovascular glaucoma.

P:  Above-normal intraocular pressure is considered to be a risk factor, but some patients seem to think elevated pressure IS glaucoma.

Dr. Elliot Werner:  Glaucoma is defined as damage to the optic nerve, retinal nerve fiber layer and/or visual field.  If they are all normal, you don't have glaucoma no matter how high your IOP is.  That doesn't mean you don't treat if the risk is high, but you need to make the proper diagnosis.

Moderator:  Is intraocular inflammation a risk factor? 

Dr. Elliot Werner:  Uveitis is a risk factor for developing a secondary glaucoma, uveitic glaucoma.  About 25% of patients with chronic uveitis develop glaucoma.

P:  I don't understand the concept of "risk factor" only having relevance in the absence of disease.  Couldn't one have glaucoma, but still properly talk about "risk factors" for progression to a more advanced stage?

Dr. Elliot Werner:  Yes, there are risk factors for progression, but they only exist in the absence of progression having already occurred.  For example, a hemorrhage on the optic disc is a risk factor for progression of glaucoma. The point is, a risk factor for anything only exists before that thing occurs.

P:  Is optic nerve damage always visible or can some damage be invisible to the examiner?

Dr. Elliot Werner:  Nothing is 100%.  Significant nerve damage is almost always fairly easy to detect, assuming the optic nerve can be seen during an examination.  Very early damage can be difficult to detect.  The sad and more important fact is that a lot of nerve damage is not detected when it should be, because a lot of eye docs aren't good enough or careful enough.

P:  I think routine eye exams can be a risk factor.  My acute-angle glaucoma was not detected for over ten years (which is how long my glaucoma specialist says I have had glaucoma.)  In March, when I couldn't read the "E" on the chart, my ophthalmologist finally checked my intraocular pressure.  All he did for ten years was observe the optic nerve.

Dr. Elliot Werner:  Badly done routine eye exams can be a risk factor. The pressure should be measured during every eye exam in every patient who is able to cooperate for the test.

P:  Earlier you described corneal endothelial dystrophy.  It sounds a lot like Chandler's.  Would you explain the difference?

Dr. Elliot Werner:  Corneal endothelial dystrophy and Chandler's are different diseases, even though they both affect the cornea and both produce corneal swelling and clouding.  Endothelial dystrophy is characterized by heaped-up material on the endothelial cells, called guttata. The cells gradually disappear and are not replaced by anything. 

Chandler's is characterized by the growth and proliferation of an abnormal basement membrane over the back of the corneal that chokes off the endothelial cells and replaces them with a membrane. 

Both clinically and pathologically (under a microscope), the two conditions look very different.  Also, Chandler's is frequently associated with a secondary glaucoma, whereas corneal dystrophy is not generally associated with glaucoma. 

Moderator:  Thank you very much, Dr. Werner.

End of highlights for June 23, 2003.

On July 2, Dr. Wilson discussed "Trabeculectomies, What's New?" in the Chat room. Click here for highlights of that meeting.

Click here for the most recent glaucoma chat highlights and links to the chat archives.

Click here for upcoming glaucoma chat events.