Glaucoma Risk Factors
Chat Highlights
August 18, 2010

On Wednesday, August 18, 2010, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Glaucoma Risk Factors".

Moderator: Welcome everyone. Tonight's topic is Glaucoma Risk Factors. Dr. Pro, one of our new chatters was diagnosed as a glaucoma suspect just yesterday, with pressures of 25 and 22.

Dr. Pro: Great topic. It's something I discuss every day. The new chatter's situation is very appropriate to tonight's topic as it is true that two of the major glaucoma risk factors are elevated IOP and increasing age. Obviously, you can't modify your age, but you can modify your IOP if treatment is indicated.

Moderator: Dr. Pro, what should our new chatter be asking a glaucoma specialist to help qualify his degree of risk? He is 29 years old.

Dr. Pro: What is the condition of my nerve? What are my other risk factors, like corneal thickness? Is my visual field normal? These and other factors are what the doctor should be thinking about and which he needs also to understand.

P: What are the other most significant risk factors for glaucoma?

Dr. Pro: Some of the others include central corneal thickness, optic nerve appearance, and performance on a visual field. These three factors and the risk factors that I mentioned above were found to increase a subject's risk to develop glaucoma in the Ocular Hypertension Treatment Study (OHTS). That was a very important study which looked at glaucoma suspects and tried to see why some people develop glaucoma and others don't. That study has helped us to stratify risk and has guided treatment decisions for many patients.

There are other risk factors that other studies have discovered. For instance, race is a risk factor. Individuals of African ancestry have a 3 to 4 fold elevated risk of developing glaucoma as an age matched person of European ancestry. Hispanics also have a higher incidence than Caucasians.
Family history is important. If you have a first degree relative with glaucoma, your chance of developing glaucoma is higher.

P: And if the familial relationship is not first degree?

Dr. Pro: Then your risk is probably no more than other individuals.

P: Is one type of glaucoma more hereditary than all others?

Dr. Pro: Some of the rare congenital and pediatric glaucomas are strongly hereditary. In those cases there may be very strong family histories of glaucoma. I have treated families where multiple children were affected.

The most common glaucoma in North America is Primary Open Angle Glaucoma (POAG). POAG is multifactorial. There are definitely some genetic risk factors which predispose some individuals, but there are also poorly understood environmental factors which are at play.

P: Is blindness from glaucoma also hereditary?

Dr. Pro: Untreated glaucoma may lead to blindness. Some forms of hereditary glaucoma are more aggressive and can lead to blindness at an earlier age. With all glaucomas, prompt and effective care can help prevent blindness.

P: Could you explain what "some forms of hereditary glaucoma are more aggressive" means? Do these forms not react to treatment?

Dr. Pro: Congenital glaucoma presents at a very young age and with high IOP. If not treated early, then the visual outcome can be poor. Also some persons have a strong family history of adult onset glaucoma where multiple family members are affected. Although we still classify this as POAG, these individuals likely have a genetic mutation. These family clusters seem to present younger and with higher IOP.

P: Our son, who is 30 years old, has only been treated for glaucoma for about six months and they are already suggesting he could have laser surgery. Yet his pressures are only about18/19 with the drops he is on. His father has gone blind from glaucoma even with treatment.

Dr. Pro: Okay. Well there is a strong family history here, which may be why the doctor is being more aggressive in treatment, but there are other issues that cause a doctor to decide to be more aggressive such as optic nerve appearance, highest IOP, thickness of cornea, etc.

P: Is any amount of nearsightedness a risk factor for glaucoma?

Dr. Pro: Yes, myopia seems to be a risk factor. We think it may be that in myopia the optic nerve is under more stress. The myopic eyeball is longer and maybe the optic nerve has less structural support.

P: My niece has Pigment Dispersion Syndrome. Can you tell us something about that? Her pressures have been running in the high twenties for years and they have recently done laser.

Dr. Pro: This is a condition where the pigment on the back side of the iris rubs off, floats around in the front of the eye, and clogs the trabecular meshwork (drain in the eye). A laser peripheral iridotomy is sometimes done to help reduce the amount of pigment that is rubbed off.

P: Is genetic testing for glaucoma available?

Dr. Pro: Not widely available. At this point academic centers like Wills have genetics labs. For many individuals with glaucoma it does not change the treatment even if a specific genetic mutation is found. Perhaps in the future there will be gene therapy for some glaucomas.

But I need to stress that the vast majority (95 percent) of glaucoma is not due to a single gene mutation. Genetic testing would not be appropriate or helpful to almost all patients at this time.

P: Is a large optic nerve considered a sign of glaucoma or a risk factor?

Dr. Pro: Good question. A large nerve can actually look much worse than it really is. The smaller nerves can be tougher as it is harder to see a defect in them. What a glaucoma specialist is looking at is the quality of the optic nerve rim. Thinning or notching of the rim is a hallmark of glaucoma.

P: Is asymmetry in any aspect related to the eye a risk factor?

Dr. Pro: Yes. Although glaucoma is usually a bilateral disease it may start in one eye first.

P: If glaucoma can be caused from steroid use, if the steroids are stopped will the glaucoma disappear?

Dr. Pro: Steroids can lead to elevated IOP. This usually occurs with chronic use. Steroid drops are more likely to cause elevated IOP, then high dose oral steroids, then other routes such as facial creams. The high IOP can eventually lead to glaucoma. Glaucoma suspects and glaucoma patients are more prone to a steroid response. The IOP usually, but not always, goes back down after the steroids are stopped. I am seeing more patients these days with elevated IOP after intraocular steroid injection for retinal diseases. These can be particularly tough to treat. Sometimes glaucoma surgery is needed for difficult steroid glaucoma.

P: Is sleep apnea a risk factor for glaucoma?

Dr. Pro: Yes. Probably for two reasons. First the breath holding may cause increased intrathoracic pressure and secondary elevated IOP. Second the apnea causes a relative decreased optic nerve perfusion which may predispose the nerve to damage.

P: What about substance abuse or excessive smoking? Do they promote glaucoma in a susceptible person?

Dr. Pro: Here the studies are not clear. One would think that smoking would be harmful, but there is not any good data.

P: Does early detection of glaucoma guarantee one has a chance not to be blind?

Dr. Pro: That is the goal of treatment. Ideally the glaucoma is detected early and treatment initiated before major nerve damage has occurred.

Moderator: That was the last question. Thank you Dr. Pro and good night.

Dr. Pro: Good night.

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