The eye drifts upward spontaneously or after being covered. The condition usually affects both eyes, but can occur unilaterally or asymmetrically. It is often associated with latent or manifest-latent nystagmus and, as well as occurring with infantile esotropia, can also be found associated with exotropias and<unk><unk> s.<unk> s are usually controlled from occurring with both eyes open, but may become manifest with inattention. Usually some level of dissociative occlusion is required - to trigger the brain to suppress vision in that eye and then not control a<unk>  from occurring. The level of dissociative occlusion required may involve using a red filter, a darker filter or complete occlusion (e.g. with a hand). Onset<unk>  typically becomes apparent between 18 months and three years of age, however, the difficulties of achieving the prolonged occlusion required for accurate detection in the very young make it possible that onset is generally earlier than these figures suggest. Mechanism == Dissociation refers to the situation where the innervation of one eye causes it to move involuntarily and independently of the other eye. Usually both eyes work together as described by Hering's and Sherrington's laws of innervation. A<unk>  is a slow upward and sometimes temporal movement of one eye, with cortical suppression of the vision in that eye while it is deviated. On returning downward and possibly inward to take up fixation, the<unk>  slow movement will be reversed. The dissociative movement seen 'objectively' should not be confused with the dissociation that occurs 'subjectively' - as when the brain begins to not visualise both images simultaneously (by ignoring or suppressing vision in that eye).
Dissociated vertical deviation
Infantile esotropia
Lipoatrophia semicircularis
Cyclotropia
Ecotropism
Ectopia cordis
Exotropia
Pseudostrabismus