Abstract: For severe otitis media with effusion, insertion of a ventilation tube is performed for the purpose of ventilation of the middle ear cavity and normalization of the eustachian tubular function and middle ear mucosa. The ventilation tube is left in place for as long as several months or even a few years. However, the influence of the indwelling tube on vibration of the tympanic membrane is unknown. Therefore, the authors observed the influence by means of time-averaged holography using human tympanic membranes. The following results were obtained. After insertion of a ventilation tube, vibration pattern of the tympanic membrane was not obviously changed, but the vibration amplitude of the tympanic membrane was decreased, especially at 500 Hz. Generally speaking, the change caused by insertion of a ventilation tube was very small. Also, the vibration pattern of perforated tympanic membrane was not changed, but the vibration amplitude of perforated tympanic membrane was decreased at the low frequency area.!
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