[Repetitive instillations of cyclosporin A eyedrop induce pupillary constriction and anterior chamber inflammation-like reactions in rabbits].

We attempted to clarify the mechanism of atropine-resistant miosis caused by repetitive instillations of cyclosporin A (CyA) eye drop in rabbits by investigating the possibility that the miosis may be attributable to CyA-induced contraction of the iris sphincter muscle, and that it may be resulting from inflammatory or inflammation-like reactions caused by CyA in living rabbit eyes. CyA did not induce contraction of the isolated iris sphincter muscle. Eight Dutch rabbits were given repetitive instillations of 0.1% CyA eye drops, and 7 rabbits (87.5%) exhibited miosis, accompanied by conjunctival and pericorneal hyperemia, and increased anterior flare 6 to 12 hours after the instillations. Fibrinoid formation in the anterior chamber was observed in 4 rabbits (50.0%). All of these findings were inhibited by treatment with anti-inflammation drugs, especially by indomethacin. After repetitive applications of 0.1% CyA eye drops, breakdown of the blood-aqueous barrier was observed in the ipsilateral iris vessels and cilliary epithelium. Increase in the aqueous protein concentration was noted, but there were no changes in the cell number. Repetitive instillations of the vehicle and single instillation of 0.1% CyA did not induce these inflammation-like findings. These results indicate that the miosis is a secondary effect resulting from ocular inflammation-like reactions and breakdown of the blood-aqueous barrier caused by excessive application of CyA.