Optic nerve hypoplasia in association with brain anomalies and an abnormal electroretinogram

Abnormal electroretinograms (decreased amplitude and prolonged implicit time > 2 standard deviations) in several patients with optic nerve hypoplasia (ONH) and developmental brain anomalies led us to study the electroretinogram (ERG) in 34 consecutive cases of ONH presenting to our practice. Ages of the subjects were between 7 months and 13 years (mean, 4 years). ERGs were recorded from each eye by means of a contact lens electrode and ganzfeld stimuli. Rod-dominated dark-adapted responses were recorded as well as cone-dominated light-adapted responses. When clinically indicated, brain imaging by either computed tomography (CT) or magnetic resonance imaging (MRI) was performed. The ERG was abnormal in 12 (35%) of the children, including five (42%) with unilateral ONH. Imaging studies of the brain in 12 children with ONH and an abnormal ERG disclosed brain malformations in nine (75%) of them compared to five (23%) in the group with ONH and a normal ERG. An abnormal ERG associated with ONH and brain malformations may represent retinal or transsynaptic degeneration beyond the ganglion cell layer and implies a shared causative mechanism.