Idiopathic congenital nystagmus is defined as conjugated, spontaneous and involuntary ocular oscillations that appear at birth or during the first three months of life. This nystagmus persists throughout life. The frequency is estimated to 1 in 1500 births. Ocular oscillations are often symmetric and usually horizontal in 95% of patients. They can persist after eye closure, however, decrease of idiopathic congenital nystagmus have been reported during non-visual tasks. Nystagmus can be classified into different categories (Pendular nystagmus, horizontal unidirectional nystagmus, bi-directional nystagmus) according to the characteristics of their oscillations: peak-to-peak amplitude, frequency, mean velocity, direction and period of foveation. This disorder is believed to be due to a primary abnormality in oculomotor control. Autosomal dominant, autosomal recessive, X-linked dominant and X-linked recessive modes of inheritance have been described. The gene that maps to chromosomes 6p12 (NYS2) is associated with autosomal dominant inheritance. The genes mapped to chromosome Xp11.4-p11.3 (NYS1) and Xq26-q27 are associated with X-linked congenital forms. There are evidences for a fourth gene in idiopathic congenital nystagmus. Complete ophthalmologic examination and electrophysiological study must be performed to rule out any ocular abnormalities causing bilateral visual deprivation or retinal dysfunction. Treatment of idiopathic congenital nystagmus aims at improving the vision. It includes correction of refractive errors, drugs and eye muscle surgery.
Last update: October 2003