An Anatomical Study of the Inferior Oblique Muscle: The Embalmed Cadaver vs the Fresh Cadaver

Abstract

PURPOSE: To determine the incidence of divided bellies of the inferior oblique (IO) muscle in embalmed and fresh cadavers, and to elucidate the symmetry of IOs in the left and right eyes.

DESIGN: Cohort study.

METHODS: IOs were dissected from their origin to the insertion point in 40 intact orbits of 20 embalmed cadavers and in 22 intact orbits of 11 fresh cadavers. The width and location of the IO origin were measured in the skull. In addition, the locations and patterns of IO insertions on the globe were recorded.

RESULTS: Divided bellies were evident in 18 of the 40 IOs (45%) in the 20 embalmed cadavers but in none of the 22 IOs in the 11 fresh cadavers. The insertional patterns of the IOs differed between the left and right eyes in 12 of 31 cadavers (39%).

CONCLUSIONS: Dehiscence attributable to the loss of intermuscular fatty tissue and shrinkage in the postmortem state could be mistaken for actual divided bellies in embalmed cadavers. Future studies should investigate the incidence of multiple insertions of IOs in a large number of fresh cadavers. In addition, ocular surgeons should be aware of the possibility of differences in the insertional anatomy of IOs between the left and right eyes.