Surgical Treatment of a Large-Angle Post Traumatic Hypertropia by The Inverse Knapp Procedure: A Case Report

urpose: To report the case of a patient treated successfully by the inverse Knapp procedure for persistent vertical diplopia, despite 2 orbital reconstruction surgeries following orbital trauma. Report: A 40-year-old patient was referred to us for a 10-months history of vertical diplopia which started after a road traffic accident. The initial CT scan had revealed right maxillary hemosinus, fracture of the orbital floor and muscle incarceration; for which he had undergone 2 orbital surgeries before referral. Ocular motility revealed a 30 Prism Diopters (PD) hypertropia and limited depression of the right eye. Lancaster test showed inferior rectus palsy of the right eye. Persistent diplopia despite 4 months of continuous patching of the left eye was the indication for surgery. The inverse Knapp procedure was done under general anaesthesia. Post operatively, the patient was free of diplopia without the use of prisms in primary gaze and in near vision. Conclusion: The inverse Knapp procedure is an uncommon operation in strabismus surgery which gives good results in inferior rectus palsy from orbital trauma.