Antihypertensive Medication Postpones the Onset of Glaucoma

Glaucoma is the second most common irreversible cause of blindness worldwide. It is becoming increasingly important in the context of an aging world population. It possesses a considerable challenge to public health because blindness and visual impairment is costly and have a huge impact on life quality. Raised intraocular pressure (IOP) remains the only successful treatable factor to reduce the progression of glaucoma. Yet, glaucoma is multifactorial, and the understanding of the pathology is incomplete. More than 2 decades ago, the first study to suggest that blood pressure (BP) should be considered in glaucoma treatment was published. Since then, the impact of BP on glaucoma has received greater attention as more evidence has mounted. Despite the increasing evidence of an association between BP and glaucoma, the exact relationship is complex. In this matter, epidemiological and case–control studies have shown diverse results, and some studies have presented evidence of a correlation between high BP and glaucoma, whereas other studies have linked glaucoma and low-tension glaucoma with low BP. The controversies have been discussed and related to the complexity of BP not only influencing IOP and ocular perfusion pressure, but also increasing the risk of compromised peripheral vascular capacity and a dysfunctional autoregulation. Recognized high BP is treated with many different antihypertensive medications, and growing evidence acknowledges that such treatment is associated with glaucoma. In this matter, antihypertensive medication may conflict with ocular perfusion and autoregulation. Although studies have shown a correlation between antihypertensive treatment and glaucoma, these studies have mostly been trials in small numbers of patients with minimal follow-up periods. Moreover, to the best of our knowledge, no previous study has benefited from a complete data sample from an entire population nor— importantly—estimated the causal effect of antihypertensive treatment on the risk of developing glaucoma. The main outcome in our study is the treatment for glaucoma. We hypothesized, before embarking on the empirical analysis, that treatment with antihypertensive medication could have an ambiguous effect on the development Abstract—The aim was to investigate the impact of antihypertensive medication on the onset of glaucoma. Data from the complete Danish population between 40 and 95 years of age were used in the period from 1996 to 2012, covering >2.6 million individuals. The National Danish Registry of Medicinal Products Statistics was used to identify all claimed prescriptions for glaucoma medication and antihypertensive drugs. We first investigated basic correlations in the data and found that patients treated with antihypertensive medication, at any time during the study period, had a significantly higher overall relative risk (RR) of glaucoma, even when controlling for age and sex (with a RR of 1.31 and P<0.0001). Furthermore, our data confirm the well-known positive association between age and glaucoma. To investigate the causal effect of antihypertensive treatment on the onset of treatment for glaucoma, we used a regression discontinuity study design. This analysis provides our main finding, namely that prescription of antihypertensive medication leads to a significant reduction in the risk of developing glaucoma. Therefore, although hypertension—as indicated by the use of antihypertensive medication—is positively correlated with glaucoma, our study indicates that antihypertensive medication itself may have a preventive effect on the development of glaucoma. (Hypertension. 2017;69:202-210. DOI: 10.1161/ HYPERTENSIONAHA.116.08068.) • Online Data Supplement