Bilateral optic nerve hypoplasia in a pup

A 6-week-old Beagle failed to respond to visual stimulation. Examination revealed fixed dilated pupils and hypoplasia of both optic disks. Results of electroretinography were normal. Radiography of the skull revealed small optic nerve foramina. Histologically, the outer layers of the retinas were normal, the retinal ganglion cells were scarce, and the nerve fiber layers, optic nerves, and optic chiasm were hypoplastic.