Purpose: Retrobulbar injections of alcohol and chlorpromazine are used for the treatment of blind, painful eyes. There have been reports of inflammation after retrobulbar injections of these agents, but the histologic effects are not well characterized. A clinical case with histopathologic confirmation of inflammation after retrobulbar alcohol injection led the authors to develop a rat model to examine these effects.
Methods: Adult Lewis rats were given retrobulbar injections of either 0.1 ml of absolute alcohol or 25 mg/ml chlorpromazine in the right orbit, and 0.1 ml of saline in the left orbit as a control. Rats were euthanized, perfused, and postfixed at 1 to 2 weeks after injection. Exenterated orbital tissue was sectioned for histologic staining. Slides were reviewed by a masked ocular pathologist who evaluated the level of orbital inflammation.
Results: Histopathology demonstrated foci of granulomatous inflammation in the orbit of the patient and similar inflammation in the rat orbits injected with retrobulbar alcohol. In the chlorpromazine group, only 1 rat demonstrated small foci of inflammation, while the control orbits injected with saline showed no inflammation. On blinded qualitative analysis, the orbits receiving retrobulbar alcohol had greater inflammation than the orbits receiving either saline or chlorpromazine.
Conclusions: Our findings in this preclinical pilot study suggest that retrobulbar alcohol injections incite significant orbital inflammation, whereas retrobulbar chlorpromazine induces little or no inflammation. This potential inflammatory response should be considered when selecting an agent for pain management, particularly if future orbital surgery is anticipated.