Who Gets Glaucoma and Why?
Chat Highlights
April 6, 2005

On Wednesday, April 6, 2005, Dr. Rick Wilson a glaucoma specialist at Wills, and the glaucoma chat group discussed "Who Gets Glaucoma and Why?"

Moderator:  Welcome to chat, Dr. Wilson and everyone.  Our topic tonight concerns who gets glaucoma and why.  Dr. Wilson, will you please start the discussion?

Dr. Rick Wilson:  The older you are, the more likely your are to get glaucoma.  A family history of glaucoma increases your risk significantly.  African Americans and those with thin corneas are at increased risk.  Obviously, those with pigment-dispersion glaucoma, pseudoexfoliation glaucoma, and those who have had eye trauma, or a retinal vein occlusion are at high risk.  Elderly Hispanics are at twice the risk of getting glaucoma as Caucasians.

Moderator:  Are some people more likely than others to get normal-tension glaucoma (NTG)?

Dr. Rick Wilson:  All the above are risk factors for open-angle glaucoma.  Japanese are more prone to NTG, which is one kind of open-angle glaucoma.  African Americans have thinner corneas and larger cups in their optic nerves.  Once you adjust for those factors, the African-American status drops out as a risk factor.  That doesn't explain why they get glaucoma about 10 years, on average, before Caucasians, so there must be a genetic predisposition that has not yet been discovered.

Moderator:  Other than Japanese, who else might be prone to NTG?

Dr. Rick Wilson:  I don't think anyone has a good idea.  NTG is almost always a disease of the elderly.  The one group that is susceptible to NTG in their 50s is individuals with low blood pressure, more often women, in my experience.

P:  What is it about a thin cornea that increases the risk of getting glaucoma?

Dr. Rick Wilson:  A thin cornea leads to an artificially low IOP (intraocular pressure) reading on Goldmann or Tonopen tonometry.   In addition, there seems to be a somewhat increased risk for glaucoma that may stem from a thinner or weaker eye wall supporting the optic nerve as it passes through on the way to the brain.

Moderator:  Why are those people more susceptible to NTG?

Dr. Rick Wilson:  I didn't say those with thin corneas are more susceptible to NTG.  A group of NTG patients will have a disproportionate number of individuals with thin corneas.  They may have elevated IOPs that are not picked up because of the artifact of low IOPs.

P:  How do you define "elderly?"

Dr. Rick Wilson:  Older than 60 years, though that age is seeming younger and younger as I get closer.

P:  A lot of women with NTG coming to this chat room during the past five years must have been fibbing about their ages.

Dr. Rick Wilson:  Some might say that is a natural trait.

Moderator:  Why are elderly people and women more prone to NTG?

Dr. Rick Wilson:  My guess would be that poorer circulation plays a significant role in NTG.  Elderly people certainly acquire that naturally.  Women are more prone to vasospastic disease and, in my office, low blood pressure.

P:  Regarding low blood pressure as a risk factor for NTG, how low do you mean?

Dr. Rick Wilson:  I'm sure it is a sliding scale, but my NTG patients often have blood pressures of 94/58 mm Hg, or will have a large drop in blood pressure during sleep.

P:  What are some of the causes of open-angle glaucoma besides genetic?

Dr. Rick Wilson:  Steroid use, trauma, plus the aforementioned causes.

P:  Does the cornea tend to grow thicker or thinner with age?

Dr. Rick Wilson:  There are modest changes in the cornea according to the time of day, during the menstrual cycle, and drying if the eyelid is held open.  But there does not seem to be a significant change in healthy corneal thickness with age.

P:  I heard that children born with primary congenital glaucoma (PCG) can have a milder or more severe form of it.  Why is that?

Dr. Rick Wilson:  The severity of the glaucoma seems to relate directly to the degree of abnormality in the development of the outflow channel of the infant.  Environment and nutrition do not seem to play a significant role, according to the knowledge we have now.

P:  Who gets angle-closure glaucoma and why?

Dr. Rick Wilson:  People with small eyes mostly get angle closure.  Women are much more prone to angle closure than men, because their eyes are smaller.  The Inuit and Chinese have very high levels of angle closure, often due not only to the smaller eye, but also to the shape of the peripheral iris that narrows the angle.

P:  Can contact lenses that are larger than the iris block the normal flow of aqueous and increase pressure, causing glaucoma?

Dr. Rick Wilson:  That's theoretically possible only if the lens was large enough and tight enough to grip the area just past the cornea, and close the aqueous veins that carry the aqueous away.

P:  Can corneal thickness change after surgery?

Dr. Rick Wilson:  Only after corneal grafts, PRK, LASIK, or if the lining of the cornea is damaged by the surgery and the cornea swells.

P:  Is high blood pressure a risk factor?

Dr. Rick Wilson:  It's important for health, but not for diagnosing glaucoma.

Moderator:  Thank you, Dr. Wilson.

Dr. Rick Wilson:  Good night, everyone.

Moderator:  Next Wednesday we will discuss making decisions about our glaucoma care.  No doctor will be here.

On April 13, the Glaucoma Chat Support Group discussed "Making Decisions" in the Chat room. Click here for highlights of that meeting.

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