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Glaucoma Dialogue IGR 9-4

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Comment by Josef Flammer on:

20036 Predictors of long-term progression in the Early Manifest Glaucoma Trial, Leske MC; Heijl A; Hyman L et al., Ophthalmology, 2007; 114: 1965-1972

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The two manuscripts study risk factors that are important in the development and progression of glaucoma in Blacks of African Ancestry and Scandinavians, respectively. While there may be criticisms regarding the generalizability of results from these two studies, the methodology and results presented in these two particular manuscripts from these studies are sound.

The major concern I have with these two manuscripts relates to how the findings pertaining to blood pressure will be applied in practice. The rapidly evolving definition of what constitutes hypertension impacts this discussion. For example, the EMGT manuscript defines low systolic blood pressure as being below 160 mmHg. Currently, a systolic blood pressure of 130 mmHg might be considered border-line high and 140-150 mmHg would most certainly be considered high. It may be that amongst patients with borderline or definitive hypertension, lower blood pressure and perfusion pressure places individuals at risk of glaucoma progression. Similarly, in the Barbados Eye Study, over half of study subjects were acknowledged to have systemic hypertension. Given the cutoffs of 140 and 90 mmHg for systolic and diastolic blood pressure respectively in the definition of hypertension, a large number of the remaining half not judged to be hypertensive may have also been borderline hypertensive. Hypertension is highly prevalent in populations of African ancestry worldwide. It may be, once again, that low blood pressure is protective against the development of glaucoma in patients who have hypertension. As hypertension causes microvascular disease, a higher blood pressure may be necessary for adequate optic nerve perfusion in such patients to overcome the resistance to blood flow caused by arteriolar narrowing. Further work is needed to determine whether or not a higher blood pressure is desirable to protect the optic nerve from glaucoma development and progression in individuals with normal or low blood pressure.

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