Is the geniculostriate system a prerequisite for nystagmus?

The time of onset of congenital horizontal nystagmus is usually known. We present a group of infants in whom this was determined objectively. In two, vertical nystagmus in the neonatal period became horizontally directed, at 4 months in one, and between 7 and 9 months of age in the second. Two infants (one an oculocutaneous albino) had no visual response initially but subsequently developed horizontal nystagmus as the vision improved at 5 and 6 1/2 months: Type III delayed visual maturation. An infant totally blind due to Norrie's disease was examined in the first week of life but did not develop nystagmus for a further 3 months. Two children with cortical visual impairment never developed nystagmus. In early infancy, vision is thought to be predominantly subcortical. Therefore the development of nystagmus at a time when the geniculostriate system is emerging functionally (around 3 months), and its absence in cortical visual impairment, has led us to propose a hypothesis suggesting that a functioning geniculostriate system is a prerequisite for the development of horizontal nystagmus.