Microanatomy of the Orbital Apex: Computed Tomography and Microcryoplaning of Soft and Hard Tissue

Abstract

The anatomy of the orbital apex is characterized by a complex interplay between critical bony and neural structures. Traditional methods used to study this region include dissection, static sections, and computed tomography (CT). Tomographic techniques are very useful in understanding these complex relationships, but the resolution of conventional CT and magnetic resonance imaging (MRI) is not sufficient to recognize the intricate details of the optic nerve canal and associated structures. The purpose of this study is to determine the value of microcryoplaning and computer reconstruction in visualizing the orbital apex in detail not previously possible, at any orientation in three-dimensional space. Microcryotomy of the orbital apex area was performed on cadaver specimens, and images of each cryosection were digitized. Subsequently, the lesser wing of sphenoid bone and optic nerve were outlined to allow for spatial manipulation and three-dimensional visualization of the orbital apex. The authors present reconstructed computer images of the orbital apex in coronal and axial planes with CT correlation. Clinically important anatomic points and landmarks as well as potential pitfalls are demonstrated. Microcryoplaning and computer reconstruction are useful techniques in viewing the detailed anatomy of the orbital apex. Although microcryoplaning has the limitation of poor soft tissue detail, the resolution of captured images is much greater than those obtained from CT or MRI scans; the improved resolution allows for accurate CT correlations. The technique has utility in education, surgical planning, and quantitative analysis of orbital apical anatomy.