An incision was made over the temporal area of the left eye; part of the lateral orbital wall (zygomatic and frontal bone) was removed, and the lateral rectus muscle was dissected. The scleral area just above the long ciliary artery was exposed, and a 3- to 4-mm incision was made through the sclera. The conjunctiva was sutured to a fixed frame attached to the stereotaxic headholder to prevent eye movements. The pupil was dilated with 5% phenylephrine hydrochloride, 0.5% tropicamide, and 1% atropine sulfate. To protect the corneal surface, a hard contact lens was placed on the cornea (polymethylmethacrylate; base curve, 8.50 mm; power, +1.5 D; diameter, 13.5 mm). All experiments were performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Visual Research, and the procedures were approved by the Animal Research Committee of Osaka University Medical School.