Frontal-eyed animals such as humans enjoy a compelling form of depth perception derived from the slightly different views our two eyes have of the same objects. This stereoscopic mechanism fails, however, if directions in which the two eyes point are not precisely coordinated. Binocular coordination is effortless for most of us, but turns out to be no simple matter, because the muscular anatomy of the two eyes is not the same (one is a mirror-image of the other), because control of a rotating object, like an eyeball, is much more complex than it seems, and because parts of the eye and brain change and develop defects as we age. Our laboratory pursues three lines of research that aim to better understand the eye positioning system.

Six muscles are primarily responsible for the movement of each eye. We developed a way to measure eye muscle forces during normal movements and found surprising differences between expected and actual forces, showing that eye muscles are much more complex than previously thought. Force measurements are important for understanding normal muscles, abnormal muscles, and muscles treated surgically and with pharmacologic agents.

A dozen years ago we proposed that the complex network of connective tissues surrounding the eye functioned as a system of pulleys, determining the mechanical actions of the eye muscles. We have recently developed 3D images of smooth muscle and elastic tissues surrounding the eye which demonstrate yet another new architectural feature of the eye, whose function is yet to be investigated.

Based on physiologic results from our studies of eye muscle forces, orbital tissue architecture, and results from other laboratories, we have developed software able to simulate normal and abnormal binocular coordination. The Orbit™ system has been useful for developing ideas about normal eye muscle function, for aiding in diagnosis and treatment of patients with eye movement disorders, and for teaching ophthalmologists and optometrists the subtleties of eye alignment.

For more information, visit Joel Miller's lab web pages.

Collaborators: Martin Weismair, Bruce Smith, Ethan Rossi, Scott Konishi. Joseph Demer, Christopher Bockish, Herschel Goldstein, Alan Scott.