Evaluation of the Infant With Decreased Vision
Family history may identify hereditary causes of pregeniculate visual impairment. Details of the pregnancy are important; factors such as in utero exposure to infection, drugs, alcohol, or radiation; trauma; and maternal diabetes mellitus may predispose to pregeniculate impairment and/or CVI. Perinatal problems such as prematurity, intrauterine growth retardation, fetal distress, bradycardia, meconium staining, and oxygen deprivation may be associated with CVI. In addition, the clinician should inquire about systemic abnormalities, delayed developmental milestones, and postnatal causes of brain injury.
Parental observations of the child’s visual behavior should be noted. In a child with CVI, visual attentiveness may fluctuate widely; the family may report that the child sometimes seems to see and at other times does not appear to see at all.
Vision in the infant is assessed qualitatively by clinical appraisal and optokinetic nystagmus responses, and quantitatively by preferential looking tests—for example, Teller Acuity Cards II (Stereo Optical, Inc, Chicago, IL) or the Cardiff Acuity Test—and visual evoked potential (VEP); see Chapter 1 for a discussion of these quantitative tests. VEP results may be either normal or subnormal in CVI. Infants with ocular motor apraxia (see Chapter 12) may falsely appear to have poor vision due to impaired horizontal eye movements, but vertical movements are usually spared.
Pupillary responses are sluggish with certain pregeniculate causes of visual impairment such as retinal dystrophies and optic nerve abnormalities. Paradoxical pupils (pupillary constriction in response to darkness) can occur with these conditions. In contrast, pupillary responses are normal in infants with CVI.
In the setting of poor vision, nystagmus in infancy should raise suspicion for sensory nystagmus due to a pregeniculate disorder (see Chapter 13). Conversely, poor visual behavior with normal ocular examination results, normal pupillary responses, and no nystagmus by 3 months of age is more likely to represent CVI or DVM. Congenital motor nystagmus usually does not present with poor vision but is occasionally associated with DVM.
Anterior segment and fundus examinations may reveal a pregeniculate cause of the visual impairment, such as bilateral cataracts, bilateral macular colobomas or scars, bilateral optic nerve hypoplasia, bilateral optic atrophy, or foveal hypoplasia with or without albinism or aniridia. However, some retinal causes of pregeniculate visual impairment may not be associated with any visible abnormalities on fundus examination. Sometimes optic nerve abnormalities may be present even though the primary cause of visual impairment is CVI: descending optic atrophy (from transsynaptic degeneration) may coexist with CVI, and in preterm infants, optic disc cupping resembling that seen in glaucoma can occur as a result of transsynaptic degeneration, most commonly secondary to periventricular leukomalacia.
If the ocular examination is unrevealing yet suspicion is high for a pregeniculate cause of visual impairment (eg, when poor vision is accompanied by nystagmus), then electroretinography (ERG) may be indicated to diagnose a retinal dystrophy. ERG results are normal in CVI.
Neuroimaging studies in CVI may be normal, in which case the visual prognosis tends to be more favorable, or may reveal changes such as cerebral atrophy, porencephaly in the occipital (striate or parastriate) cortex, damage to the optic radiations, or periventricular leukomalacia.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.