Orbital tissues and eye rotations

Anuchit Poonyathalang1 Sangeeta Khanna2 R John Leigh2 1Department of Ophthalmology, Ramathibodi Hospital, Bangkok, Thailand; 2Neurology Service, Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, Ohio, USA Abstract: Recent discoveries about the orbital tissues prompt a re-evaluation of the way that clinicians think about disorders affecting the extraocular muscles, their nerves and motoneurons in the brainstem. The revolutionary discovery that the orbital layers of the extraocular muscles insert not onto the eyeball, but into fi bromuscular pulleys that guide the orbital layers, provides explanations for the kinematic properties of eye rotations and clinical fi ndings in some patients with strabismus. The demonstration that all extraocular fi bers types, except pale global fi bers, lack synaptic folding provides an explanation for why saccades may remain fast in patients with limited ocular mobility due to myasthenia gravis. More than one mechanism may account for the observation that patients with disorders affecting the eye muscles or their nerves can present with the appearance of central disorders of ocular motility, such as internuclear ophthalmoplegia. New approaches to analyzing saccades in patients with disjunctive eye movements provide the means to identify disorders affecting the peripheral or central components of the ocular motor system, or both.