Development of a laser holography otoscope for diagnosis in the clinic

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Conductive hearing loss, usually associated with middle-ear disorders, is the most common reason for otologic surgery. The pathogenesis of conductive loss includes, among others, acute middle-ear infection, chronic middle-ear infection, diseases of the ossicular chain (e.g. otosclerosis), trauma to the head or ear and pathologic third-windows of the inner ear. Surgical treatments for conductive hearing loss range from the simple (myringotomy and tympanostomy tube insertion) to the complex (total reconstruction of the middle ear after mastoidectomy). While acute infections and middle-ear effusion are relatively easily diagnosed on otologic examination, the cause of conductive loss with an intact tympanic membrane (TM) and dry middle ear is not easily determined. Furthermore, while tympanoplasty is a common procedure after chronic middle-ear disease (with over 500 such procedures performed in our institution each year), the hearing outcome after these procedures is highly variable. Our fundamental hypothesis is that both (a) the pre-surgical diagnosis of conductive-hearing disorders with intact TM and (b) the evaluation of causes of surgical failure in ossicular and TM reconstructions can be improved by measurements of the sound-induced motions of the TM. This hypothesis is supported by our analyses of full-field-of-view holographic measurements of sound-induced TM motions in animals and temporal bones. These measurements were gathered using a prototype holographic system that is currently used as a research tool at the MEEI. This proposal will aid in the translation of the available holographic platform into a compact holographic device for measurements of the motions of the visible TM in live patients. The new device will be designed for use in a clinical environment and it will be developed via a cooperative venture between the optical measurement experts within the Mechanical Engineering Department of the Worcester Polytechnic Institute and auditory scientists and clinicians at the Massachusetts Eye and Ear Infirmary.