John S. Stahl, M.D., Ph.D., is an Associate Professor of Neurology at the Case Western Reserve University School of Medicine and a Staff Neurologist at the Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Dr. Stahl is a Principal Investigator of the Daroff-Dell'Osso Ocular Motility Laboratory with both VA Merit Review and NIH-NEI funding.

1. Coordination of head and eye movements in humans. When humans (and other mammals with retinal foveas) shift the direction of gaze, they can do so by moving the head and eyes together or the eyes alone. In contrast, mammals without retinal foveas rarely shift the eyes without moving the head as well. We use recordings of eye and head movements in normal humans to investigate the mechanisms underlying the ability to dissociate eye and head movements.

2. Eye movement control in mouse models of human vestibular and ocular motor disease. The modern tools of genetics provide the ability to identify and modify the genes underlying the development and control of the vestibular and ocular motor systems. The genetic tools are particularly well developed for the laboratory mouse, but assessing vestibular and ocular motor function in the mouse has been difficult, owing to its small size. Our laboratory developed a video method of recording eye movements in the mouse, and is engaged in studying vestibular and ocular motor function in a variety of mouse mutants. We have a particular interest in strains carrying mutations of CACNA1A, the gene encoding the pore component of the P/Q voltage-activated calcium channel. These mutations are responsible for several human disorders, including familial hemiplegic migraine and familial episodic ataxias. Studies of these mutants offer insight into the role of the cerebellum in eye movement control, both in normal and disease states.

3. Diagnosis and treatment of disorders of eye movements that impair vision. In collaboration with Dr. R. John Leigh, we characterize eye movements in a variety of human neurologic diseases. A current major focus is on developing an electronic/optical aid to improve visual function in patients with involuntary oscillation of the eyes due to multiple sclerosis or stroke. The system monitors eye movements and optically shifts the image of the seen world, locking it to the moving retina. In this way vision is rendered stable and clear despite the continued oscillations.