Purpose: To determine the causative factors of persistent diplopia after retrobulbar anesthesia.
Setting: Strabismus Section, Department of Ophthalmology, Seoul National University, Seoul, South Korea.
Methods: Prism and alternate cover tests in the diagnostic positions of gaze and ductions/versions were performed in 28 patients with persistent diplopia 6 months after retrobulbar anesthesia. The Lancaster test, Bielshowsky head tilt test, double Maddox rod test, fundoscopic examination for torsion, forced duction test, force generation test, tensilon test, thyroid function test, and/or orbit computed tomography were performed when necessary.
Results: Most of the patients (26 patients, 93%) did not have diplopia before retrobulbar anesthesia. Of the 14 patients with extraocular muscles imbalance, 12 patients showed vertical rectus overaction (11 superior recti, 1 inferior rectus) and 2 patients, mild vertical rectus underaction. Nine patients were presumed to have a sensory strabismus related to the preoperative poor vision, but this went unnoticed preoperatively. Three patients showed a small vertical deviation without any specific causative factors.
Conclusions: Fifty percent of the cases of diplopia were associated with either direct trauma or anesthetic myotoxicity to the extraocular muscles, in which overactions were more common than underactions. Thirty-two percent of the patients were presumed to have sensory strabismus, which suggested the importance of preoperative examination for strabismus as well as providing an explanation about the risk of postoperative diplopia before surgery.