We injected diltiazem into the left lateral rectus muscles (LR) of 10 rabbits in order to examine the ultrastructural effects of diltiazem on rabbit extraocular muscles and estimate its advantages in clinical use as an alternative to the surgical therapy of strabismus. The animals were divided into two groups according to the time of evaluation following the injection. The LR muscles of both eyes of the first group were respected 60 min after the injection, for ultrastructural examination. The same procedure was done for the second group at the 24th hour The right eyes were used as the control group. There was a medial shift 3-5 min following the injection in the left eyes of both groups. The ultrastructural examination revealed weakness in muscle contractility, probably as a result of inhibition of glycogen usage due to calcium accumulation. In this study, we examined the early clinical and ultrastructural effects of diltiazem.