General Description of

Research on Eye-Head Coordination

and Vestibular Neurectomy-Labyrinthectomy

at UCLA

Principal Investigator: Joseph L. Demer, M.D., Ph.D.

The management of dizzy patients has undergone continued improvement with the advent of new surgical interventions, medical therapies, and rehabilitation strategies. These therapeutic advances have created a pressing need to develop more refined diagnostic tests whose results can more accurately relate to patient symptoms. In particular, there is a need to develop tests of vestibular function that are relevant to daily activities and the natural challenges faced by patients. A combination of technological advances and improved understanding of physiological principles now affords the opportunity to implement new tests of vestibular system function.

The overall objective of the UCLA Human Vestibular Laboratory is to improve the diagnosis and treatment of patients complaining of dizziness and disequilibrium. This project involves development of new tests to evaluate these conditions. The laboratory studies normal subjects and patients with documented or suspected lesions of the inner ear and brain that impair balance. Studies are performed using a battery of quantitative tests, some previously developed and new tests under development. The quantitative data from the vestibular tests along with appropriate statistical comparisons with normative data are made immediately available to the examining physician. The goal of the research is to systematically characterize the features of all the common causes of dizziness and disequilibrium.

In brief, each test administered to adult human volunteers consists of a stimulus and a response measurement. Test stimuli include 1) visual targets, either moving or stationary, 2) a turning or sliding motion to the subject produced by a chair driven by a motor, 3) a treadmill, and 4) a platform (upon which the volunteer stands) that moves slightly up and down or back and forth. Either eye movements or sway of body parts are the response measurements. Eye movements are recorded by 1) electrodes pasted on the skin around the eyes (electro-oculography), 2) optical tracking of the eyes, or 3) magnetic coils embedded in a specifically designed contact lenses riding on the whites of the eyes surrounding the cornea. The first two techniques are routine for recording horizontal (back and forth) eye movements used in clinics throughout the country, while the contact lens method is the only reliable method for accurately recording vertical (rotation up and down) and torsional (rotation around the line of sight) eye movements. Postural sway is measured by a platform that contains vertical force sensors beneath the volunteer's feet. Motion of body parts, such as the head, is measured using magnetic motion sensors comfortably strapped to the body. Vision is also tested using computerized techniques during motion of the volunteers years, or motion of the eye charts. Some tests are repeated after a period of wearing prismatic or magnifying spectacles. Appropriate safeguards have been incorporated to protect all volunteers.

We plan to study approximately 40 normal subjects and 40 patients per year. Since dizziness and disequilibrium is not gender-specific, we will study approximately 50% men and 50% women. Normal subjects and patients range in age from 18 to 90 years so that we can asses the effect of aging on balance function, and distinguish the effects of normal aging from the effects of disease. Normal subjects are required so that we can develop a normal range for the balance measurements. Some tests are repeated on an ongoing basis in volunteers who have undergone surgeries on the inner ears or vestibular nerves (nerves to the inner ears), so that we can investigate how the brain adapts to specific deficiencies of inner ear function. This is a longitudinal study without a specific ending point.

Dr. Joseph Demer, M.D., Ph.D., Professor of Ophthalmology and Neurology, and Jun-Ru Tian, M.D., Ph.D., Assistant Research Ophthalmologist, are responsible for the research and for obtaining informed consent. The research procedures are all conducted in the UCLA Medical Center, and are headquartered at the Jules Stein Eye Institute, UCLA. This research is financially supported by the U.S. Public Health Service, National Institute on Deafness and Communicative Disorders, and by the benefactors of the Jules Stein Eye Institute.