Extraocular proprioception and new treatments for infantile nystagmus syndrome.

Our goal is to develop the proprioceptive hypothesis for nystagmus damping; and present the resulting therapies for the treatment of infantile nystagmus syndrome (INS) and acquired nystagmus. Contact lenses, cutaneous stimulation, and neck-muscle vibration damped INS. Four-muscle tenotomy and reattachment was hypothesized as a treatment for INS in 1979 and successfully demonstrated to improve foveation in a canine model of INS and seesaw nystagmus in 1998 and in humans with INS (masked-data, NEI Clinical Trial) in 2003. Subsequently, tenotomy successfully damped acquired pendular nystagmus and oscillopsia in two MS patients and downbeat nystagmus in another. Tenotomy, used in isolation or combination with existing nystagmus and strabismus surgeries, damps different types of nystagmus in their plane of action. Recent neuroanatomical and neurophysiological discoveries support the hypothesis that proprioception is the mechanism for INS damping and allow more realistic models of peripheral ocular motor pathways.