Oculomotor Abnormalities in Albinism

Although there are anatomic abnormalities in the sensory system (foveal hypoplasia and misrouting of retinofugal projections, the abnormal ocular movements observed (spontaneous unidirectional and bidirectional jerk or pendular nystagmus and absent true horizontal OKN) are not simply explained (Table 1). Foveal hypoplasia leading to degraded sensorimotor feedback does not explain the vertical stability nor the presence of nystagmus at or soon after birth particularly since the anatomic development of the fovea is not normally completed until 4 months after birth. Moreover foveal hypoplasia is an obligate feature of albinism while nystagmus is not. The alternative hypothesis is that optic pathway abnormalities result in directional errors of senorimotor feedback. The problem with this explanation is the need to explain the other forms of congenital nystagmus not associated with abnormal retinal projections.