Chapter 113 Wobbly eyes in infancy
Jiggly or wobbly eyes in infant are often first spotted by a family friend or relative, sometimes before they are noticed by the parents. Sometimes what is more noticeable is the associated strabismus, ocular structural abnormalities, e.g. microphthalmos, or poor visual responsiveness. The parents ask: What is the problem, can it be repaired, and can or will the child see? The two main issues are the spontaneous abnormal eye movements and any accompanying impairment of vision.
The most important saccadic disorder is the bursts of spontaneous saccades, multidirectional, often part of a startle response, seen as an early manifestation of the generalized clonic movements that sometimes accompany a neuroblastoma. This “opsoclonus” should prompt the physician to investigate for this treatable tumor although opsoclonus may be part of the benign “dancing eyes and dancing feet” syndrome of childhood.
Spontaneous jiggling of the infant’s eyes is more commonly due to nystagmus, which can be regarded as either ocular or neurologic in origin. The ocular types, more often seen in infants, can be due to some form of visual impairment (sensory infantile nystagmus) or idiopathic (formerly referred to as a motor congenital nystagmus).
Nystagmus can take many forms in its movement (usually variations of pendular and jerk type of oscillations), as well as in direction and speed. Some movements form a pattern that is helpful in diagnosis, but, many times, other clues in the history or examination lead to the definition of the problem. Some patterns of nystagmus are highly characteristic and suggestive of an ocular problem while, less commonly, others suggest a topographically localizing neurological problem.
The history of prenatal/natal difficulties (maternal diabetes, drug ingestion, difficult delivery) and a neonatal and developmental course need to be considered as well as the child’s visual responsiveness, ocular symptoms (poor vision, photophobia, head nodding, strabismus), and the family history of any visual impairment and nystagmus.
Most infantile nystagmus disorders show horizontal oscillations, but sometimes vertical, rotatory, or a combination of several planes of movement occurs. Visual fixation may appear to be good, or vision may be poor. Sometimes, the eye movements are typical of idiopathic infantile nystagmus, sometimes called “congenital nystagmus” or “motor congenital nystagmus” (horizontal, variable in intensity, changing with gaze movements, dampening by convergence, increasing with visual effort, and no conversion to vertical nystagmus on vertical gaze, i.e. remaining horizontal on vertical gaze). A null point with compensatory head turn may be present. Nystagmus on the basis of sensory defects (sensory congenital nystagmus) may appear similar. It is not always possible to detect milder degrees of associated visual loss. Vertical nystagmus in infants is more often ocular in origin than neurological. Severe visual impairment commonly produces more irregular, slow, wandering horizontal movements with intermittent vertical jerking and little response to the usual visual stimuli and optokinetic testing. Very valuable is the history of the time of onset of the nystagmus, because visual system gliomas may masquerade as forms of infantile nystagmus with good vision, even the so-called “congenital nystagmus” and spasmus nutans. In most cases, infantile wobbly eyes are recognized early in life, but sometime the “time of onset” may be unclear. A useful rule is that in cases with onset not recognized until after approximately 3 months of age, neuroimaging of the head and visual system, preferably with MRI, should be carried out to rule out structural brain abnormalities.
Latent, or occlusion nystagmus, often accompanies infantile esotropia, with or without congenital nystagmus. This is a binocular horizontal jerk form of oscillation, precipitated by occlusion of one eye, resulting in conjugate nystagmus jerking toward the fixating eye. Sometimes, the same form of nystagmus exists without being initiated by occlusion, usually in the presence of strabismus, but is further exaggerated by occlusion, i.e. a spontaneous binocular deficiency nystagmus syndrome (sometimes called by the oxymoron “manifest” latent nystagmus). Latent nystagmus is a motor sign of strabismus-related developmental loss of binocular vision and, for isolated cases, usually requires no electrophysiologic or neurological investigation.