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Editors Selection IGR 7-2

Systemic hypertension and glaucoma

Comment by Selim Orgül on:

12399 Systemic hypertension and glaucoma: mechanisms in common and co-occurrence, Langman MJ; Lancashire RJ; Cheng KK et al., British Journal of Ophthalmology, 2005; 89: 960-963

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Langman et al. (564) examined the link between the preponderance of a diagnosis of systemic hypertension and a diagnosis of glaucoma. They also analyzed the effect of intake of various substances used to treat systemic hypertension on the likelihood to diagnose glaucoma and, finally, because steroids may have a bearing on both, systemic hypertension and glaucoma, scrutinized a potential association between intake of oral steroid treatment and a diagnosis of glaucoma.

The General Practitioner Research Database was used to identify glaucoma patients and, in these patients, as well as in age and sex matched randomly chosen controls from the same database, the frequency of documented systemic hypertension or raised blood pressure was sought. In case of a lack of association between the diseases, a 10% preponderance of systemic hypertension was expected among glaucoma patients. With regard to the definition of the conditions, the authors solely relied on the records.

Considering in the glaucoma group only patients who had been diagnosed with systemic hypertension prior to being diagnosed with glaucoma, the authors found that a previous diagnosis of systemic hypertension or a record of elevated blood pressure made it significantly more likely for glaucoma to be diagnosed, but that the use of systemic betablockers, independently of the reason for such a treatment, made a diagnosis of glaucoma significantly less likely, while the use of ACE inhibitors, calcium channel blockers or diuretics increased the likelihood of such a diagnosis. Patients under systemic betablockers and with a diagnosis of systemic hypertension and/or a record of raised blood pressure had a lower risk of being diagnosed with glaucoma, but only when diuretics were taken concurrently, while those treated with betablockers but without a diagnosis of systemic hypertension or a record of raised blood pressure had a lower risk only when no diuretics were taken. The increased risk of being diagnosed with glaucoma under ACE inhibitor or calcium channel blocker treatment was only present in patients with a diagnosis of hypertension and/or raised blood pressure, independently of concurrent intake of diuretics. Finally, the likelihood of being diagnosed with glaucoma was significantly increased in steroid takers.

The authors thoroughly analyze their data, but in studies like this, where the diagnostic criteria have not been scrutinized in great detail, it is unlikely that questions such as whether systemic hypertension is rather related to glaucoma or simply to increased intraocular pressure can be unraveled. The authors had no means to analyze the association between systemic hypertension and glaucoma, but only to analyze an association between a diagnosis of systemic hypertension and a diagnosis of glaucoma. It would be of utmost importance to know the exact criteria used to diagnose these conditions and whether the criteria were applied uniformly throughout the study period (January 1990 through 31 December 1999). Indeed, glaucoma has lately been defined differently from earlier views and, especially, intraocular pressure has been excluded from the definition. Therefore, caution is also warranted when the authors conclude that betablockers may have a bearing on a disease such as glaucoma. It could well be that this substance reducing intraocular pressure, and the diagnosis of glaucoma relying on the presence of increased intraocular pressure, the effect of betablockers was simply limited to its effect on the accuracy for diagnosing glaucoma. Accordingly, the findings pertaining to the other substances scrutinized in this article are very difficult to interpret. It is possible and even likely that rather than the substances themselves, the conditions for which the different treatments had been instituted were the cause for a higher likelihood of being diagnosed with glaucoma. One can only imagine the impact an erroneous interpretation of this study could have on the number of law suits for inducing glaucoma with substances used to treat cardiovascular conditions. Consequently, this study raised several questions, but, apparently, without being able to answer them. It will be of utmost importance for future projects with databases that the exact criteria used to define various conditions can be verified throughout the observation period.

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