A 72-year-old man had right-eye conjunctival injection, chemosis, eyelid edema, and pain with eye movements. Examination showed visual acuity of 20/50, reduced ocular motility in all gazes, proptosis, and chemosis. Treatment with vancomycin and ceftriaxone and ampicillin-sulbactam was followed by symptom worsening. What would you do next?