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Editors Selection IGR 12-1

Bloodflow: Ocular perfusion pressure and OAG

Comment by Fotis Topouzis on:

26794 Distribution of ocular perfusion pressure and its relationship with open-angle glaucoma: the singapore malay eye study, Zheng Y; Wong TY; Mitchell P et al., Investigative Ophthalmology and Visual Science, 2010; 51: 3399-3404

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In a cross-sectional, population-based study of 3280 Malays 40 to 80 years old, Zheng et al. (1216) assessed the association of ocular perfusion pressure (PP) with open-angle glaucoma (OAG). Among 3261 persons available for analyses, 131 OAG cases and 3130 non-glaucoma cases were identified. In multiple logistic regression models adjusting for intraocular pressure (IOP), age, sex and IOP- and blood pressure (BP)-lowering treatment, OAG risk was significantly higher in subjects with diastolic BP (DBP), mean PP (MPP) and diastolic PP (DPP) in the lowest quartile, compared to those in the highest quartile. Also, in subgroup analyses, the association between DPP and OAG was stronger in younger (< 60 years old) than in older persons (> 60 years old), in lower IOP (< 16 mmHg) than in higher IOP (≥16 mmHg) and in females than in males. The Singapore Malay Eye Study findings are an important contribution to the literature, given that this is the first population-based study to confirm the association between low DPP and OAG in an Asian population, thus providing further evidence on a vascular component in the multifactorial OAG process. The population-based study design, the standardization of procedures and the adjustment for potential confounders in statistical analyses are among the strengths of the study. However, as acknowledged by the authors, not all study participants underwent visual field testing, which is a limitation of this study. Further, one may not exclude potential misclassification of glaucomatous subjects with small optic disc cups as non-glaucomatous, based on the International Society for Geographical and Epidemiological Ophthalmology (ISGEO) criteria for glaucoma diagnosis used in this study.

This is the first population-based study to confirm the association between low DPP and OAG in an Asian population

Similarly to previous studies, the investigators found a dramatic increase in OAG prevalence below a certain level of DPP (< 50 mmHg). However, when both DPP and IOP were included as explanatory variables in the nonlinear model, there was only a weak association of DPP with OAG prevalence. This is not a surprising finding, since IOP is a factor with major effect in OAG risk. On the other hand, the stronger association of DPP and OAG found in younger compared to older patients is an unexpected result.

One should consider that the potential effect of antihypertensive effect on OAG risk may be different depending on the BP level

Defective vascular autoregulation is more probable in the older age, which may be a surrogate for the duration of hypertension. This is being supported by the Baltimore Eye Survey, where young hypertensives were less likely to have OAG compared to non-hypertensives, while older hypertensives were more likely to have OAG compared to non-hypertensives. Finally, the investigators reported that they did not find any association between antihypertensive treatment and OAG risk. However, one should consider that the potential effect of antihypertensive effect on OAG risk may be different depending on the BP level and it is unclear whether such an analysis was conducted in this study.

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