Esotropia is a variety of heterotropia in which there is manifest inward turning of the visual axis of one eye; the term is synonymous with convergent strabismus. It may be demonstrated using the cover test as an outward movement of the eye which is forced to assume fixation by occlusion of the other eye.
Esotropia may be associated with congenital latent nystagmus (i.e., nystagmus appearing when one eye is covered) in the presence of amblyopia; the slow phase in the viewing eye is toward the nose.
With lateral rectus muscle paralysis, the eyes are esotropic or crossed on attempted lateral gaze toward the paralyzed side, but the images are uncrossed. Acute esotropia has been described following contralateral thalamic infarction.