LOW-FREQUENCY MASKING FOR DETECTION OF ENDOLYMPHATIC HYDROPS IN PATIENTS WITH GLAUCOMA

The coincidence of various eye and ear abnormalities has been describe d in the literature. Some authors discuss the possible existence of en dolymphatic hydrops in patients with glaucoma. Whereas the current dia gnostic tests for glaucoma are well-defined and evident, those for end olymphatic 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-freq uency masking tests in 23 patients with primary open-angle glaucoma wi thout signs of Meniere's disease. The phase dependent sensitivity of t he organ of Corti to a short test stimulus can be measured by applying a low-frequency masker tone to determine the modulation depth. Wherea s the modulation depth in the normal hearing population is around 20-3 5 dB, the modulation depth in patients with Meniere's disease may be s ignificantly 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 mechanism s and their histological characteristics, e.g. melanocytes and their h ormonal and enzymatic regulation, will be discussed. If the common pat hogenesis of eye and ear lesions is better understood, it may be possi ble to develop new and more effective strategies for prevention and th erapy. (C) 1998 Elsevier Science B.V.