Effect of botulinum toxin injections into rabbit eye

The aim of this study was to investigate the adverse effects of the intraocular injection of botulinum toxin in rabbits. Intravitreal injections of botulinum toxin A in five doses, 1.25, 2.5, 5, 10, 25 units, were given into five rabbit eyes. The same volume of saline was injected into the second eye of the rabbit as a control. External examination, ophthalmoscopy, visual evoked potentials and electroretinography were done before injection and repeated at the first and second weeks after the injection. There were no significant differences in retinal function between toxin- and saline-injected eyes, neither ophthalmoscopically nor electrophysiologically. Ipsilateral mydriasis developed in the eyes injected with botulinum toxin. This study suggests that botulinum toxin has no harmful effect on retinal function.