Should You get Uptight if You have both Glaucoma and High Blood Pressure?

An article by Leske et al published in the March 2002 Archives of Ophthalmology called "Incident open-angle glaucoma and blood pressure" presents an interesting paradox. In a study involving 2989 black participants performed at Barbados in the West Indies, over a four-year period, the researchers concluded that individuals at risk of getting the open angle form of glaucoma, and who are also hypertensive, not only do not show an increased risk but may actually end up with less of a risk. Suppose we examine this a bit more closely.

First of all, why only blacks rather than blacks, whites, yellows, etc.? Well, it has been well established that individuals of African descent have a greater risk of open angle glaucoma as well as hypertension. I suppose that you now have the right to say, "I'm not black, so what does all this have to do with me?" A good point, however, you may not be black, but if you have both open angle glaucoma and high blood pressure you do have two of the three criteria, so I would advise you to tune in.

If you are still with me, you might also like to know that prior studies have indicated that all of the following are apparently directly related to increasing the risk of the glaucoma: Getting older, having a higher intraocular pressure, and having relatives with the same condition. Suppose, on the other hand that you have a low blood pressure. Theory says that you have to first compare blood pressure to the pressure moving fluids in or out of the eye - perfusion pressure. If the blood pressure is lower, then the optic nerve may not receive adequate perfusion resulting in loss of the visual field. Theory also says, if you have high blood pressure, you may risk damage to the small vessels of the optic disc. It's beginning to look like you can't win unless your blood pressure is perfectly normal according to theory. One more point - there is known to be a positive correlation between your blood pressure and your intraocular pressure, so it would seem that a higher blood pressure would help increase your intraocular pressure. Now add in the findings from this study and confusion reigns, especially if you're an older patient whose getting medication to lower your blood pressure, and you also have open angle glaucoma.

Okay, what were the results of this study in any event? Using statistical methods to measure adjusted relative risk it was found that for persons with normal blood pressure the risk of getting open angle glaucoma increased markedly over the four-year study period the higher the intraocular pressure was to begin with. But, if an individual has high blood pressure to begin with, as time goes by, the risk actually decreases until, four years later, it's only about half of what it was to begin with. In other words, as I noted at the beginning, the risk of getting open angle glaucoma in these black patients who have high blood pressure when first checked does not increase the risk of the glaucoma, and may even decrease it. It was also found that those individuals whose perfusion pressure was lower when the study began were at danger of as much as a 3-fold increase in relative risk of getting open angle glaucoma. This latter finding agrees with the idea that there is a definite relationship between what goes on in your blood vessels and what goes on inside your eyes.

Finally, to get back to the question of relevance to whether you are from a different race, the authors did take the trouble to point out that there is good reason to question limiting a study to a single race, and then trying to extrapolate it to the rest of the world. Nevertheless, they tend to favor the current concept that the environment is more important and state that "no major ethnic/racial differences in open angle glaucoma risk factors have been reported, supporting the general relevance of our results." So there you have it - those readers who stuck with this review to the end in spite of not having an African ancestry can probably accept the results as pertaining to them just as well.

Five years from now, if they are still around, the authors hope to be able to report on what happens after nine years. Stick around and find out.

Cartoons and Poems following each article are created and copyrighted by Dr. Ackerman and cannot be copied or reproduced without his permission. Copyright © 2006 by Marvin Ackerman, M.D.

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