Nystagmus, often described by parents as “shaky eyes” or “dancing eyes,” is a condition characterized by involuntary, repetitive eye movements in infants. These movements are typically rhythmic and uncontrolled, occurring without the baby’s intention or awareness. Nystagmus is a common reason for parental concern and requires investigation by an eye specialist, as it is a sign of an underlying issue rather than a standalone diagnosis.
Understanding Infant Nystagmus
Infantile Nystagmus is an involuntary, rhythmic oscillation of the eyes that occurs within the first six months of life. This movement pattern can manifest in different directions, most commonly horizontal (side-to-side), but sometimes vertical (up and down) or torsional (circular) movements are also seen. The oscillation can take two main forms: a pendular waveform, where the eye movements are equally fast in both directions, or a jerk waveform, which involves a slow drift away from the target followed by a fast, corrective movement back towards it.
The condition is classified into Infantile Nystagmus Syndrome (INS) and acquired nystagmus, which develops after six months of age. INS is often an isolated oculomotor abnormality, meaning the eye structures are otherwise normal. Acquired nystagmus points to a cause that developed later in the child’s life. The involuntary nature of the movements limits the time the eye can steadily focus on a target, known as foveation time, which directly impacts visual acuity.
Causes and Underlying Conditions
Nystagmus requires a thorough investigation because it signals various underlying issues. Causes are typically grouped into those related to sensory deficits, which prevent clear visual information from reaching the brain, and those that are primarily neurological or motor in origin. A significant portion of cases are linked to these sensory deficits.
Common sensory causes include structural eye abnormalities, such as congenital cataracts or issues with the retina or optic nerve. Conditions like albinism, which involves a lack of pigment and often results in foveal hypoplasia (underdevelopment of the central retina), are highly associated with nystagmus. Neurological causes, though less common, involve developmental problems in the brain or pathways controlling eye movement. Identifying the specific etiology is the most important step, as the cause dictates the overall outlook.
Prognosis and Developmental Timelines
Whether nystagmus resolves depends entirely on the specific cause identified. A rare, transient form known as spasmus nutans typically resolves spontaneously, usually between the ages of one and three years. However, Infantile Nystagmus Syndrome (INS) is generally chronic, meaning the eye movements persist throughout life.
Even when chronic, the intensity of nystagmus often improves with increasing age, particularly within the first year and a half to two years of life. During this developmental period, the amplitude of the eye movements tends to decrease, and the foveation time increases, allowing for improved visual development. For children with INS not associated with a sensory deficit, visual acuity can still improve alongside motor development. Although the eye movements may not disappear completely, overall visual function can develop well.
Management and Treatment Approaches
Management strategies focus on maximizing the child’s visual potential and reducing the severity of eye movements. The primary treatment involves correcting refractive errors, such as nearsightedness or astigmatism, using glasses or contact lenses. Corrective lenses can sometimes diminish nystagmus intensity, with contact lenses potentially offering more stable visual input than glasses.
Some individuals adopt an anomalous head posture, or head turn, to utilize a “null point” in their gaze where eye movements are minimized, thus improving vision. If this head posture is severe and causes neck discomfort, surgery, such as the Kestenbaum procedure, can be performed to reposition the eye muscles. This surgery does not eliminate the nystagmus itself, but it shifts the null point to a more comfortable, straight-ahead position, allowing the child to view the world more easily. Certain medications, such as gabapentin, have shown promise in decreasing the amplitude and frequency of oscillations and improving visual function, though a specialist must carefully consider their use.