An Overview of Glaucoma
Chat Highlights
July 12, 2006

On Wednesday, July 12, 2006, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "An Overview of Glaucoma."

Moderator:    Welcome back to chat, Dr. Wilson.  Tonight the topic is “An Overview of Glaucoma.”

Dr. Rick Wilson:    Good evening, everyone. I’m ready to start when you are.

Moderator:   Is glaucoma the most common eye disease in older people?

Dr. Rick Wilson:   No, cataracts come in number one.  Macular degeneration causes more disability than glaucoma in Caucasians, but glaucoma is number two in African Americans.  Diabetic retinopathy is gaining on the others, with the super-sizing of Americans.

P:    “Super-sizing” ?

Dr. Rick Wilson:   Americans are getting fatter and fatter.  That leads directly to an epidemic of diabetes, with type II (adult type) now being seen in children.  The earlier the onset of the disease, the more the likelihood of severe diabetic retinopathy causing visual disability.  Every pound of fat contains a mile of capillaries, so obese people also have high rates of heart disease and hypertension.

P:   Speaking of diabetes, Colin McGuckin, professor of regenerative medicine at the University of Newcastle in Ireland, has made a major breakthrough in the field of adult stem cell research by producing insulin needed by diabetic patients from the stem cells from the umbilical cords of living babies.  McGuckin said that producing insulin-secreting cells from cord blood is pretty much a first.

Dr. Rick Wilson:   There is no doubt that diabetes will be one of the first diseases to be a focus of a stem cell breakthrough.  We need to be able to inject healthy stem cells into the pancreas and have them grow into insulin-producing cells.

P:   How many people in the world are affected by glaucoma?

Dr. Rick Wilson:   In 2010, 60.5 million people are expected to have glaucoma, increasing to 79.6 million by the year 2020.  Women will be disproportionately affected by glaucoma, making up 60% of all glaucoma cases in 2010.  Africa has the largest proportion of its population with glaucoma in the over 40-year-old segment of the population, although Europe, China, and India have a larger number of people with glaucoma.

P:   Why will women be disproportionately affected by glaucoma?

Dr. Rick Wilson:   Because women live longer and the prevalence of glaucoma increases markedly with age. More women have glaucoma than men.  Women also have slightly higher IOPs (intraocular pressure) than men and more normal-tension glaucoma (NTG) than men.

P:   What is normal-tension glaucoma?

Dr. Rick Wilson:   It’s damage to the optic nerve that results in characteristic changes in the optic nerve and the visual field.  The intraocular pressure is normal.

P:   Are African-Americans at increased risk for glaucoma?

Dr. Rick Wilson:   African-Americans are about 3.5 times more likely to have glaucoma, about six times more likely to be blind from it, but only half as likely as Caucasians to be treated for it.
African-Americans are usually diagnosed 10 years earlier than Caucasians, and are 14 to 17 times more likely to go blind from glaucoma between the ages of 45 and 65 than Caucasians.

P:   How many people in the U. S. are blind due to glaucoma?

Dr. Rick Wilson:   Approximately 130,000 Americans are blind (best-corrected visual acuity less than or equal to 20/200 or visual field less than 20º) from primary glaucoma.

P:   About how many people have glaucoma, but don’t know it because they don’t get regular check-ups?

Dr. Rick Wilson:   Five to seven million people worldwide are blind from all types of glaucoma. High IOP and/or glaucoma are markers for decreased life expectancy.  About half of the total number of people with glaucoma are unaware they have it.

P:   Why are high IOP and/or glaucoma markers for decreased life expectancy?

Dr. Rick Wilson:   No one knows. Perhaps glaucoma is to some extent a vascular disease, and people prone to glaucoma damage might also be prone to other vascular problems.  That’s just a wild guess.

P:   Why is glaucoma called the silent thief of vision?

Dr. Rick Wilson:   Because it has no symptoms until the disease is extremely advanced.  Yesterday I saw a man who was told 20-some years ago that he was at risk for glaucoma.  Because he had no symptoms, he didn't see an ophthalmologist until he had lost all vision in one eye and 80% of the optic nerve in the other eye.  People are unaware of their visual loss until they are disabled in some way.  The loss of visual field is so slow (like watching hair grow, only slower) and central vision is not lost until near the end.

P:   Is vision loss from glaucoma reversible?

Dr. Rick Wilson:   There seems to be a stage in the progression from healthy to death in the retinal ganglion cell when the cell has been injured to the extent it is no longer functioning, but is still alive. If the IOP can be lowered sufficiently, those cells in that stage can return to functioning.  There is a slight increase in vision in many people after they have a significant drop, say 40%, in their IOP.

P:   Does the most glaucoma damage often occur before the patient sees an ophthalmologist?

Dr. Rick Wilson:   Yes. We are quite good at stopping progression in most patients.

P:   When the vision loss in my left eye was discovered in 1988, a neuro-ophthalmologist said he thought the loss may have started 10 years earlier.  No optometrist had noticed it.

Dr. Rick Wilson:   That is why I mentioned “ophthalmologist” earlier.  I know a good number of optometrists who are excellent diagnosticians, but most are not as astute as ophthalmologists.

P:   Does the optic nerve need to be examined to rule out glaucoma?

Dr. Rick Wilson:   Yes.

P:   Does the pupil have to be dilated for a good examination of the optic nerve?

Dr. Rick Wilson:   Usually.

P:   The diagnosis and treatment of glaucoma have greatly improved, but have any advances been made in preventing glaucoma?

Dr. Rick Wilson:   Prevention is mainly seen with angle-closure glaucoma.  Patients with eyes in which the iris is too close to the trabecular meshwork and may become caught in it, blocking outflow of fluid from the eye, can be treated with a laser iridectomy.  That prevents the onset of glaucoma with a high degree of certainty.

P:   Would a general ophthalmologist recognize that an iris is too close to the trabecular meshwork?

Dr. Rick Wilson:   He should by doing a gonioscopy; that is, by looking into the angle of the eye with a mirrored device.

P:   Can you tell by examining an optic nerve whether the damage occurred over weeks, months, or years?

Dr. Rick Wilson:   Usually, the rate of glaucoma damage is related to the height of the eye pressure, unless there are other contributing factors, such as low systemic blood pressure or a cardiac arrhythmia (grossly irregular heart rate), etc.

P:   Can you explain more about the relationship of low blood pressure to glaucoma?  This is the first time I have heard of that relationship.

Dr. Rick Wilson:   Glaucoma usually happens when the eye pressure is high, injuring the nerve.  One theory of the mechanism by which the damage to the nerve occurs is that the IOP is so high that the heart has trouble pumping blood into the eye against that pressure to get blood to the optic nerve.  If the eye pressure is normal, but the body blood pressure is low, the same situation occurs.  That is, the blood does not have enough pressure to pump it into the eye where the optic nerve starts.

P:   Is there a relationship between the cup-to-disc ratio and loss of the optic nerve?

Dr. Rick Wilson:   Since the cup-to-disc ratio in normal eyes depends upon the size of the scleral canal leaving the back of the eye, some normal people have no cup.  Others, including my son, have 0.85 cups.  Therefore, in general, larger cups connote increased risk, but on an individual basis, a large cup could be normal or not, depending upon what the size of the cup was before the glaucoma started.

P:   If there are still signs of some healthy optic nerve remaining in a person with advanced glaucoma, but no usable vision, is there any hope that some vision will return on its own or with medical advancements?

Dr. Rick Wilson:   There is only one nerve from each eye to the brain.  The nerve cannot be somewhat healthy and have advanced glaucoma. With advanced glaucoma, the visual field is much more of a help in determining the extent of the disease than the appearance of the optic nerve. In 10 to 15 years, stem cell therapy may be able to repopulate the retina and optic nerves of a patient with advanced damage due to glaucoma.

Moderator:   Dr. Rick, It is now past 9:30 p.m.  Thank you for your time.

Dr. Rick Wilson:   You’re welcome. Dr. Jeff Henderer will join you next Wednesday.  Please welcome him warmly.  I'll be back in two weeks.

On July 19, Dr. Henderer discussed "Who is at Risk for Glaucoma" in the Chat room. Click here for highlights of that meeting.

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