Standardized intravitreal injections: evaluation of the effect of anesthesia on rapid axonal transport in the optic nerve.

Retinal ganglion cells incorporate intravitreally injected [3H]leucine into proteins that are transported orthogradely in optic axons to the superior colliculus. Since optic projections in the albino rabbit are nearly totally crossed, an agent suspected to alter axonal transport can be applied to one optic nerve after bilateral intravitreal injection of [3H]leucine; any reduction in radioactivity transported to the contralateral superior colliculus can then be quantified. Such studies require symmetric uptake and incorporation of precursor into ganglion cell proteins. A technique is described for intravitreal injections that reproducibly produces symmetric uptake of [3H]leucine. Using this technique, we determined that retrobulbar injected lidocaine in clinically used doses (2-4%) does not affect rapid axonal transport, while colchicine (a known inhibitor of axonal transport) blocks transport in a dose-related fashion.