Dissociated visual development: electrodiagnostic studies in infants who are 'slow to see'.

Four infants were studied who failed to show any visual interest or following responses in the first three months of life. Although no definite ocular abnormalities were found at the time of presentation, both the parents and their medical advisers initially had serious concerns about the infants' visual prognosis. Initial electroretinograms (ERG) were found to be unequivocally normal, but three of the infants showed absent or impaired cortical visual evoked responses (VER). The fourth infant had an initial VER which was immature. Subsequently, all the infants showed increasing visual responsiveness from three to four months of age and all now have visual behaviour and general development appropriate to their ages. The VERs were repeated after four months of age and all showed normal responses. It is concluded that poor or even absent VER responses in early infancy may not always indicate a poor prognosis for vision. The possible mechanisms of this visual maturational lag are discussed.