Blow out fracture of orbit is defined as fracture of one or more of its internal walls. This injury is typically caused by blunt trauma to orbit. In pure terms this definition does not involve the orbital rim. If fracture of orbital rim is associated with fractures of one or more of its internal walls then the term complex blow out fracture is used. Even though there is nothing complex about it, this term is used to stress the importance of non involvement of orbital rim in blow out fracture. Blow out fracture is actually a protective mechanism which ensures that sudden build up of intraocular pressure which could be detrimental to vision does not occur following frontal injury to orbit.
History: Blow out fracture of orbit was first described by Lang in early 1900's. The exact description of the fracture and the terminology (blow out fracture) was first coined by Converse and Smith. It was infact Smith who first described inferior rectus entrapment in between the fractured fragments, causing decreased ocular mobility.
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