We thank Kountouras and associates for their interest in our article. We acknowledge their research on the association of Helicobacter pylori infection with neurodegenerative and other diseases. However, the association between H. pylori infection and glaucoma remains controversial. Specifically, the above association, initially found by Kountouras and associates in a case-control study of 41 glaucoma patients and 30 anemic controls, was not confirmed in an independent study from Canada involving 97 patients and 94 controls and in a more recent study from Israel involving 51 glaucoma patients and 36 controls. Also, in another study from India of 100 glaucoma patients and 50 controls, the mean level of anti- H. pylori immunoglobulin G positivity in the sera was not statistically significantly different between subjects with primary open-angle glaucoma and the control group, whereas it was higher in controls compared with the pseudoexfoliative glaucoma group. In the same study, the level of anti- H. pylori immunoglobulin G titers did not differ between the pseudoexfoliative glaucoma and the control groups. All of the above studies have the inherent limitations of the case-control design in investigating risk factors for a disease. Further, because glaucoma prevalence increases with age and H. pylori infection is very common in the older age groups, it is very difficult to determine whether there is an association between these 2 conditions or whether the reported associations have resulted from chance alone. For all of the above reasons, H. pylori infection has not been established as a potential risk factor for glaucoma, and therefore has not been included in recent major reviews on risk factors for glaucoma.
Based on the current state of evidence, we did not investigate the potential role of H. pylori infection in glaucoma in the Thessaloniki Eye Study. Moreover, at the time that the Thessaloniki Eye Study was designed, the potential association between H. pylori infection and glaucoma had not been reported. Given that evidence for H. pylori infection being a risk factor for glaucoma is still conflicting and that population-based studies provide the best design to investigate risk factors for a disease, in retrospect it would have been desirable for us to have looked into this assocation, so as to determine more definitely whether H. pylori infection is associated with glaucoma.