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Dissociated vertical deviation (DVD) is an eye condition which occurs in association with a squint, typically infantile esotropia. The exact cause is unknown although it is logical to assume it is from faulty innervation of eye muscles.〔 == 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 DVD 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 DVD 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). == Characteristics == 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 vertical deviations. DVD'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 DVD 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). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dissociated vertical deviation」の詳細全文を読む スポンサード リンク
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