Upbeat nystagmus in a 3.5-year-old boy.

Upbeat nystagmus is usually a central vestibular nystagmus attributable to structural brainstem or cerebellar lesions. Adult-onset upbeat nystagmus calls for a thorough neurological evaluation. In children, however, it can occur as a transient phenomenon in healthy neonates or as a sensory form of nystagmus that usually transforms into horizontal nystagmus by 2 years of age. We report the case of 3.5-year-old boy with upbeat nystagmus. His ocular examination was within normal limits. Neurological evaluation was normal. Optical coherence tomography testing and Electroretinogram confirmed cone dysfunction. Over the next 6 months the upbeat nystagmus converted to horizontal nystagmus.