The coincidence of various eye and ear abnormalities has been described in the literature. Some authors discuss the possible existence of endolymphatic hydrops in patients with glaucoma. Whereas the current diagnostic tests for glaucoma are well-defined and evident, those for endolymphatic hydrops are not so reliable. This has made it difficult to accurately study the coincidence of endolymphatic hydrops and glaucoma. For better detection of endolymphatic hydrops, we performed low-frequency masking tests in 23 patients with primary open-angle glaucoma without signs of Ménìere's disease. The phase dependent sensitivity of the organ of Corti to a short test stimulus can be measured by applying a low-frequency masker tone to determine the modulation depth. Whereas the modulation depth in the normal hearing population is around 20-35 dB, the modulation depth in patients with Ménière's disease may be significantly decreased (5-10 dB), depending on the stage of disease. A decreased modulation depth was found in at least one ear in 19 of our 23 patients with glaucoma. Correlations between homeostatic mechanisms and their histological characteristics, e.g. melanocytes and their hormonal and enzymatic regulation, will be discussed. If the common pathogenesis of eye and ear lesions is better understood, it may be possible to develop new and more effective strategies for prevention and therapy.