Our case appears to be a very rare case of autosomal dominant aplasia of MR seen in a male patient and his 2 sons. In all 3 cases, MR was not absent on the magnetic resonance image, which only showed mild hypoplasia; however, the intraoperative findings showed only a thin sheath of muscle capsule. As pointed out by Demer et al,3 the orbital and global fibers have differences in fiber types, fiber sizes, electromyography characteristics, vascular content, and metabolic activity. It is speculated that these cases had a lack of development of global fibers but complete development of orbital fibers. More research is needed into this differential development of the extraocular fibers in the future.