Experimental Contracture of Superior Rectus Muscle : Period for Development of Contracture

It is not rare to confirm the extraocular muscle contracture clinically in case of antagonist paralysis. Precise discriptions, however, regarding the development of the contracture of extraocular muscles have not been mentioned in previous reports. The rabbit superior rectus muscle was contracted without stretch by the antagonist. The inferior rectus muscle was extirpated. It was confirmed that the remnant of the inferior rectus muscle was attached behind the equator of the eyeball. Mild contracture of the superior rectus was observed 90 days after the operation for in vivo and in vitro. But we couldn't find out any significant morphological change by use of a light microscope. Contracture of the superior rectus muscle was observed 360 days after the operation, histologically. Hypertrophy of slow fibers and an increase of the connective tissue in the slow muscle fiber bundle were observed. In conclusion, the functional contracture occurred within 90 days after the extirpation of the antagonist, however, histological changes were demonstrated within 360 days.departmental bulletin pape