Infantile Nystagmus Syndrome
Infantile nystagmus syndrome (INS) refers to nystagmus that appears during the first six months of life. Although nystagmus may arise from an abnormality of the eyes, it can also arise as a result of a subtle imbalance of the eye movement mechanism within the brain.
Ocular albinism, optic nerve abnormalities, congenital cataracts and retinal dystrophies are the common ocular anomalies that may cause nystagmus.
Children with INS require a prompt pediatric ophthalmologic evaluation to rule-out characteristics that may suggest a serious neurologic cause of the nystagmus.
Most patients with nystagmus will have an identifiable null zone. That is, there will be a position of gaze where the nystagmus is least and therefore vision is best. This may cause a habitual abnormal head posture. For an example, if the nystagmus null zone is present when the child gazes upward, then a chin-down head posture will be present to place the eyes in up gaze. Alternatively, if the nystagmus null zone is present when the child gazes toward the right, then a left face-turn head posture will be present to place the eyes in right gaze.
Child with albinism demonstrating chin-down posture (left photo) as null zone is in up gaze. Note normal head posture following corrective eye muscle surgery (right photo).
Eye muscle surgery is very effective for two reasons in pediatric and adult patients with INS. For those patients with abnormal head postures due to an “eccentric” nystagmus null zone as described above, surgery can center the null zone thus eliminating the habitual abnormal head posture. Additionally, even in INS patients without abnormal head postures, simple “horizontal rectus tenotomy” surgery can significantly reduce the severity of nystagmus and establish a broader null zone.
The surgeons at Pediatric Ophthalmic Consultants regularly perform successful nystagmus surgery.