—Small children with nystagmus whom ophthalmologists encounter most often have congenital nystagmus (CN). However, other causes of nystagmus should be sought. The most important are neurologic disorders, since the child's general health can be at risk and early medical intervention might be needed. Therefore, I emphasize detecting neurologic disorders by seeking neurologic signs and symptoms and looking for nystagmus characteristics that are uncommon in CN, eg, vertical and torsional directions. Neuroradiologic tests are not used routinely, but are performed when neurologic disorders are suspected.I agree with Dr Brodie that electrophysiologic tests, such as electroretinography, are useful in detecting some ocular abnormalities associated with nystagmus. The nystagmus can usually be distinguished from CN. For example, nystagmus associated with rod monochromatism often has a higher frequency and/or smaller amplitude than CN.1 Congenital nystagmus has characteristic waveforms that can be revealed by eye movement recordings in young children.
Yee RD. Choice of Initial Tests for Nystagmus in Infants-Reply. Arch Ophthalmol. 1991;109(4):464. doi:10.1001/archopht.1991.01080040024006