Decompression operation of the optic canal via the nasal path under endoscope is widely used, but it is both a challenging and controversial method. Unsatisfactory results were largely associated with otolaryngologists' limited understanding of the real anatomical situations of the optic canal before operation. To provide otolaryngologists with the real situations and data preoperation, multislice helical CT was used to reconstruct the images of the optic canal. Using multislice helical CT-aided three-dimensional reconstructive methods in combination with direct anatomic measurement, we dissected and analyzed the shape of the optic canal and its anatomic relationship with the adjoining structures in 40 intact postmortem skull samples. The In-Space technique clearly showed the structure and the related region of the optic canal. The virtual endoscopy technique showed superbly the spatial appearance and topography of the inner optic canal and also gave the inner structure of the optic canal optically. There was no statistic difference in three-dimensional reconstructive data with that obtained by anatomical measurements and thus can be used to directly instruct the clinic operation. These results demonstrate that a combined In-Space technique with virtual endoscopy can accurately define the subtle structure and the related region of the optical canal. In conclusion, multislice helical CT-based three-dimensional reconstruction is of important value for clinical operations. Anat Rec, 2008. © 2008 Wiley-Liss, Inc.