Ultrastructural and immunohistochemical study on the effect of topical cyclosporin A in the rabbit eye.

The effect of topically administered cyclosporin A (CyA) was evaluated in this experimental study by means of transmission and scanning electron microscopy, and immunohistochemistry. CyA dissolved in sterile olive oil was injected in the retrobulbar area and in the subconjunctival space, or administered as eyedrops in both non-grafted and corneal xenografted rabbit eyes. The vehicle rather than the drug was thought to be responsible for the inflammatory reaction observed in the conjunctiva of the injected eyes as well as for the surface epithelial defects developing in the cornea of the topically administered eyes. CyA was found to be effective in prolonging the survival of the xenografts after 1 month follow-up. The immunohistochemistry indirectly demonstrated the CyA effectiveness in impairing the T-cell function, and this is, to our knowledge, the first documented report on this subject. We conclude that another type of vehicle for the drug has to be introduced and that the administration of CyA as eyedrops is the best route to provide fast diffusion and to avoid adverse side effects.