Spastic entropion occurs as a primary event in essential blepharospasm. It is a term that is often incorrectly used to describe the overriding of the tarsal plate by preseptal orbicularis which causes corneal irritation and secondary muscle spasm. Correction of any lid laxity and repair of the loss of contact between lid retractors, tarsal plate and skin is all that is usually required. If there is a primary spastic problem, then use of botulinum toxin is a possible temporary measure to be followed by limited excision of orbicularis oculi if a more permanent solution is required. Involutional entropion, often incorrectly termed spastic, is dependent on ageing change allowing tone to relax in the retractors and orbicularis muscles. Canthal ligaments stretch and the tarsal plates develop a less rigid structure with the deposit of more elastin. The sheer size of the tarsal plate is thought to determine whether the tarsus everts or inverts in such circumstances.
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