What decides the nature of extraocular muscle injury? The probable mechanism of flap tear and rupture.

The assessment of nature and the extent of extraocular muscle injuries during initial visit in ocular emergencies is of paramount importance to avoid/minimize the subsequent need for strabismus surgery. Based on our experience in managing acute globe and orbital injuries and cases of strabismus, we propose the probable mechanism involved in the occurrence of extraocular muscle flap tear and a complete rupture of the muscle. During high-velocity injuries when the forces are equally transmitted along the orbital bony framework and the globe, then due to differential shearing forces created between the global and the orbital fibres leads to a flap tear. In the second scenario, if the forces are only directed along the bony framework, then the globe continues to be in continuous motion leading to increased tension between the muscles and the globe. Thus the weaker portions between these two structures are at risk of complete separation, that is along the insertion of muscle onto the globe or the musculotendinous portion.