The eyelid and its contribution to eye movements.

Lid and electromyographic recordings have contributed significantly to our understanding of clinical lid disorders. Tonic lid disorders (e.g. ptosis, blepharospasm, lid retraction, blepharocolysis) can be distinguished from dynamic lid disorders (lid lag) and from specific deficits of eye-lid coordination (e.g. lid nystagmus). Electromyographic recordings allow the identification of specific lid disorders that benefit from effective therapeutic interventions, e.g., botulinum toxin injections. Rapid lid closure (blink), which exerts substantial neural influence on oculomotor systems without obscuring vision, can be used for the diagnosis of brainstem disease.