Microsurgical Anatomy of the Orbit: The Rule of Seven
Figure 7
(a) The anterior fossa floor and roof of the orbit have been removed and the orbital contents dissected to expose the topographical relationships between the ethmoidal canals and the roof of the nasal cavity and orbit. The ethmoidal canals are related with the anterior and posterior limits of the ethmoidal cribriform plate. Anterior to the anterior ethmoidal canal is the frontal portion of the anterior fossa, and posterior to the posterior canal is the area of the planum sphenoidale. Similarly, anterior to the anterior ethmoidal canal is the bulbar part of the orbit, between both canals is the retrobulbar part, and posterior to the posterior ethmoidal canals is the orbital apex. (b) Sagittal cut through the left orbit, exposing its medial wall. The anterior ethmoidal canal is on average 21 mm from the medial orbital edge. The posterior ethmoidal canal is around 14 mm posterior to the anterior canal, and the optic canal is on average 7 mm posterior to the posterior canal.
