Walsh & Hoyt: Latent (Occlusion) Nystagmus

True latent nystagmus is a horizontal jerk nystagmus that is absent when both eyes are viewing but appears when one eye is covered. This conjugate nystagmus is characterized by quick phases of both eyes that beat toward the side of the fixating eye. In most patients, a low-amplitude nystagmus is also present when both eyes are viewing, and is called ""manifest latent nystagmus."" It apparently occurs because only one eye is fixating, and vision from the other deviated eye is suppressed. Latent nystagmus usually reverses direction upon covering of either eye. In some patients, however, it is present when one eye is covered but is absent when the other is covered. Occasional patients can control their latent nystagmus at will. Latent nystagmus is usually associated with strabismus, typically esotropia. Amblyopia is frequent, whereas binocular vision with normal stereopsis is rare. Latent nystagmus has been described in identical twins.