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Comment by Makoto Araie 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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Ocular perfusion is regulated to maintain constant blood flow, to the retina and optic nerve head despite fluctuating blood pressure and intraocular pressure. In glaucoma patients, however, defective vascular autoregulation may result in ischemic damage to the optic nerve head and retina. Abnormal ocular blood flow has long been linked to OAG in many small prospective trials using various ima-ging technologies. Population-based studies have also consistently identified ocular perfusion pressure deficits in glaucoma including: the Baltimore Eye Survey, Egna-Neumarkt Glaucoma Study, Long Island Case Control Study, Barbados Eye Study and Proyecto VER investigations. Building upon this concept, Leske et al. present data on predictors of long-term progression in the Early Manifest Glaucoma Trial (EMGT). Specifically, lower systolic perfusion pressure, lower systolic blood pressure and cardiovascular disease history emerged as new predictors, suggesting a definite vascular role in glaucoma progression.

These large population-based studies provide strong evidence for the relationship between vascular deficits and the prevalence, incidence and progression of glaucoma

This new study complements the work Leske and colleagues performed in the Barbados Eye Study which followed persons at risk for glaucoma, finding predictors of glaucoma to include low systolic blood pressure and ocular perfusion pressures, which more than doubled the risk of OAG incidence. Another population-based study, the Thessaloniki Eye Study, similarly associated decreased diastolic blood pressure and perfusion pressure with increased cupping and decreased rim area of the optic disc in non-glaucoma patients.These large population-based studies provide strong evidence for the relationship between vascular deficits and the prevalence, incidence and progression of glaucoma.

One significant limitation in both studies is the absence of any direct measure of ocular blood flow using imaging technologies

The strengths of these studies include a truly long-term follow up of 11 years (EMGT) and nine years (Barbados) and the inclusion of both treated and non-treated patient cohorts (EMGT). Strong participation rates (81% to 85% Barbados) and large numbers of participants (3,222) add to the quality of the results. One significant limitation in both studies is the absence of any direct measure of ocular blood flow using imaging technologies. Direct assessment of ocular blood flow in these studies might have revealed the relationship between low perfusion pressure and blood pressure on the one hand and retinal and optic nerve head blood flow on the other. Future population-based studies should include direct measurements of ocular blood flow to further explore these relationships.

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