Utility of trypan blue in identifying damaged extraocular muscles in orbital trauma: a case report

Complete rupture or avulsion of an extraocular muscle after orbital trauma is rare, and intraoperative identification of the retracted muscle stump may be difficult when the surgical field is distorted by hemorrhage and edema. Trypan blue 0.1% is a vital dye that stains muscle sheaths and tendons without staining sclera or muscle fibers, and has been described in strabismus reoperations and lost-muscle recovery. Its use during acute exploratory surgery for orbital trauma has not, to our knowledge, been reported.

We report a 30-year-old woman who presented with binocular vertical diplopia three days after blunt trauma to the right eye during a syncopal fall. Examination showed right hypertropia in primary position with a -3 limitation of depression. Orbital computed tomography showed no fracture but suggested discontinuity of the inferior rectus muscle belly. Same-day exploratory surgery was performed under general anesthesia, with intraoperative application of 0.1% trypan blue.

Exploration revealed complete laceration of the inferior rectus 6 mm from its insertion, with the distal stump adherent to Tenon's capsule and Lockwood's ligament in a field distorted by hemorrhage and edema. Trypan blue selectively stained the muscle sheaths, allowing the distal inferior rectus stump to be distinguished from surrounding connective tissue, and disclosed an additional partial avulsion of the temporal portion of the inferior oblique not identified on computed tomography. The proximal stump of the inferior rectus was resected and the distal stump reinserted 6.5 mm from the limbus with 6-0 polyglactin sutures. At last follow-up, three months after surgery, she reported no diplopia in primary position, upgaze or downgaze, with good alignment in primary position and mild residual limitation of depression and abduction of the right eye.

The dye altered intraoperative management in two ways: it confirmed the identity of the distal inferior rectus stump before reinsertion, in a field where torn muscle and hemorrhagic connective tissue were not reliably distinguishable by inspection; and it disclosed injury to the inferior oblique, the landmark conventionally used to locate a retracted inferior rectus. Trypan blue is not required in every case of orbital trauma. It may, however, be a useful adjunct in selected acute explorations where tissue planes are obscured and conventional landmarks are themselves injured.