Biofeedback in Idiopathic Infantile Nystagmus Syndrome

Background:

Infantile idiopathic nystagmus (IIN) or congenital motor nystagmus is most common among infantile nystagmus cases. It has a characteristic waveform eye movement pattern with an exponentially increasing velocity slow-phase followed by a saccadic fast phase.

IIN is present from infancy but usually recognized few months into life and may even be evident only after the child has reached several years of age. Characteristics of IIN include the following: conjugate eye movements with equal frequency and amplitude in each eye, gaze position does not change the direction of fast phase, a null point may be present with less motor instability, convergence achieves better motor stability, head turn and head tilt present to facilitate viewing at null point and absence of oscillopsia in most cases.

When the patient is asymptomatic no treatment is required. However, if the visual acuity is decreased with abnormal head posture and oscillopsia interventions are warranted.

Traditional used therapies include muscle surgery, optical devices, drugs and botulinum toxin injections. All current available therapies aim at changing the functional balance among eye muscles responsible for eye movements with hope that they will produce better ocular stability and better foveation time for incoming images with better vision. All such cases also require Low Vision Rehabilitation interventions to improve functional vision and Quality of Life.