Inferior rectus pulley hindrance: A mechanism of restrictive hypertropia following lower lid surgery

Purpose This article describes a new mechanism of restrictive strabismus associated with inferior rectus (IR) pulley hindrance complicating lower eyelid surgery. Methods We studied five patients who developed hypertropia in infraduction after bilateral lower eyelid surgery. Complete ophthalmologic examination and multipositional, high-resolution orbital imaging by computed X-ray tomography (CT), or magnetic resonance imaging (MRI) was performed. Comparison was made with MRI in normal volunteers. Results There was restriction to passive infraduction of the involved eyes. Sagittal MRI images showed hindrance to normal posterior shift of the IR pulley from central to infraducted gaze. Intraoperative findings of contracture of the inferior fornix and dense fibrous scar tissue from the inferior orbital rim to the IR pulley complex correlated with restricted infraduction and imaging findings. Release of the scar tissues around the IR pulley improved infraduction, reducing or eliminating diplopia. Conclusion Scar formation hindering anteroposterior travel of the IR pulley system is a novel mechanism of restrictive hypertropia in infraduction following lower eyelid surgery. This restrictive strabismus, the iatrogenic equivalent of retroequatorial myopexy, is distinct from paralytic strabismus and must be managed differently. Avoidance and treatment of this complication of lower eyelid surgery requires knowledge of anatomical relationship between the IR pulley and lower eyelid.