Evidence of direct damage to extraocular muscles as a cause of diplopia following orbital trauma

Vertical diplopia following orbital trauma has frequently been attributed to entrapment of the inferior rectus muscle. The high incidence of spontaneous recovery and negative forced ductions suggests that a significant percentage of these patients have other causes for their diplopia, such as direct damage to the extraocular muscles or their innervating nerves. In five patients with blunt trauma to the orbit, high-resolution computed tomography (CT) scanning showed evidence of hemorrhage or edema within the inferior rectus or inferior oblique muscle that was paretic on clinical exam. No evidence of entrapment was noted in any of the five patients. The course was variable. Three patients had almost complete recovery, whereas two demonstrated improvement but with residual restriction or paresis. Our findings support direct extraocular muscle (EOM) damage as the primary cause of diplopia in these patients. High-resolution CT scanning helps in selecting such patients in whom orbital intervention is unnecessary. The clinical goals of binocular single vision in primary and reading positions are emphasized.