[Topography of the human ciliary muscle]

The human ciliary muscle of the eye of a 48-year-old male enucleated at surgery for an adenoid cystic carcinoma of the lacrimal gland was studied regarding the morphological characteristics of the anterior apical part of the muscle, including the three-dimensional microstructure. In the anterior serial transverse sections from the most anterior level in which the meridional, radial and circular muscle fibers were recognized, the circular muscle layer anteriorly decreased, whereas the radial muscle layer increased in ratio. Thick muscle fiber bundles immediately below the outermost meridional muscle fiber layer repeated to merge and divide with neighbouring bundles on every side and indicating a complicated structure. In the scleral spur, the apical part of the muscle fiber bundle showed a very thin lamellated layer and terminated between the stromal tissue of the scleral spur indicating a strong interconnection with stromal tissue by a muscle-tendon junctional structure basically similar to the muscle-tendon junction in the striated muscle.