Evaluation of Vision within First 4 Months of Life

Parents may report that their baby does not appear to look at them. This statement requires the physician to document a history of prematurity, fetal distress, anoxia, or birth trauma carefully. A failure to reach developmental milestones may indicate neurologic abnormalities. A history of seizure disorder, cerebral palsy, or chromosomal abnormalities helps identify potentially serious causes. In this case, visual acuity or the child's ability to fixate must be assessed. Normal newborns follow faces. By age 2 or 3 months, infants normally follow light and high-contrast objects. Assessment of vision can be achieved by using an optokinetic nystagmus drum. Oculomotor disturbances may be the underlying cause of the child's apparent visual inattention. Bilateral cranial nerve III palsy, congenital fibrosis syndrome, or partial cranial nerve III palsy may give this impression as well.

Searching or roving eye movements are a form of profound nystagmus, with little foveal perception. Nystagmus is an important sign of decreased vision, indicating visual acuity often in the range of 20/200. The onset is usually at birth or shortly thereafter. The nystagmus can be a jerk or pendular nystagmus. The direction should be characterized as horizontal, vertical, or rotary.

Abnormalities of the anterior portion of the eye can cause profound visual loss and are easily visible with a +10 magnification. They include corneal opacities (leucoma) caused by congenital glaucoma, Peter's anomaly (abnormal cornea and lens), and leukocoria (white pupil) related to congenital cataracts, inflammatory disease, or retinal disease.

Evaluation of the posterior aspect of the eye, including examination of the red reflexes, may indicate an early retinal detachment or retinoblastoma. Optic nerve abnormalities may be associated with midline CNS defects, such as an absent septum pellucidum, agenesis of the corpus callosum, or hypopituitarism. Optic nerve abnormalities such as optic nerve hypoplasia are associated with nystagmus. CT or magnetic resonance imaging (MRI) can identify these abnormalities. Electroretinography (ERG) may be helpful for determining the cause of decreased visual acuity. An abnormal ERG is seen with Leber's congenital amaurosis, congenital achromatopsia, and congenital stationary night blindness. Visual-evoked potential testing may be necessary to determine whether vision is intact.

Some infants who have a completely normal eye examination but demonstrate poor fixation may actually have a delay in maturation of the visual system. Normally, the initial visual system development matures by 4 to 6 months of age. Visual-evoked potential acuities are about 20/400 during the first few days of life and improve to about 20/40 by 6 months of age. In some patients, visual-evoked responses and clinically assessed visual function may be abnormal, only to improve between 4 and 12 months of age. Although incompletely defined, in delayed visual maturation the vision is decreased, but the ocular examination appears normal, including brisk pupillary response to light. Typically, there is no nystagmus, and ERG is normal.

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