Dovepress to the significance of elevated intracranial pressure in cases of high-tension glaucoma. Elevated intracranial pressure is also considered as a characteristic finding in AD. Wostyn et al22 addressed the quite complex issue of CFS pressure, AD and glaucoma: they correlated early stages of AD with elevated CSF pressure and later stages with decreased CSF pressure. They also highlighted the importance of a high translamina-cribrosa pressure difference in the development of glaucoma.20–22 Apolipoprotein e gene and glaucoma An additional field of research into links between AD and glaucoma focuses on the apolipoprotein (APOE) gene and its variations. The gene is implicated in brain cholesterol and amyloid metabolism, and its APOE-ε4 variation is regarded as one of the major predisposing factors for the development of AD.23 It is also responsible for decreased capacity of nerve cells in response to stress and for delayed rehabilitation after stroke or head trauma.24–26 This is the reason that many scientists have worked on the putative association of the gene with glaucoma. Zetterberg et al27 focused on the issue in a study of over 400 subjects and found no such correlation. Tamura et al,6 Ressiniotis et al,28 and Lake et al29 in older similar studies also obtained negative results, even for normal tension glaucoma, which would theoretically leave more “room” for genetic factors like APOE to work as glaucoma precipitating factors. Al-Dabbagh et al,30 on the contrary, in a study performed on 230 Saudi individuals, found a positive correlation between the Apoe-ε4 allele and the development of primary open-angle glaucoma, and, in addition, found a protective role of the ε-3 allele against the disease. Saglar et al31 also performed a genetic study on 75 patients with POAG and 119 control individuals and found no correlation between the polymorphisms of the APOE, tumor suppressor protein 53 (p53) and cyclin-dependent kinase inhibitor 1A (p21) genes on one hand and POAG on the other. However, Lam and associates32 concluded in a genetic study performed on 400 Chinese individuals that APOE–ε4 is associated with glaucoma, but by acting as a protective factor against it. Pseudoexfoliation glaucoma is a form of secondary glaucoma, which is characterized by ocular accumulation of fibrils containing amyloid-related proteins, thus probably sharing common features with AD. Krumbiegel et al33 however, in a meta-analysis comprising two European (one German and one Italian) cohorts, with over 1000 participants, found a negative correlation between APOE polymorphisms and this disorder. Clinical Ophthalmology 2011:5 Alzheimer’s disease and glaucoma Conclusion Many important studies have supported the connection between AD and POAG. These data derive from epide- miological, experimental and clinical laboratory studies. These results, however, are contradicted by a series of other equally significant studies: this shows that the etiology of both AD and POAG is complex and warrants further focused investigation. The existing data justify an elevated level of clinical awareness for the diagnosis of glaucoma in AD patients and vice versa. Hopefully, future research will shed light on the issue to the benefit of these two large categories of patients. Disclosure The authors report no conflicts of interest in this work. References 1. 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