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Eric Ahn, Milap Mehta, Julian Perry; Positional Relationship Between the Ethmoidal Foramina and the Optic Canal. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3044.
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To determine the position of a ray comprised of the anterior and posterior ethmoidal foramina as it bisects the optic canal.
A prospective case series evaluating human skulls was performed between May 2012 and June 2012 at the Cleveland Museum of Natural History. Data collected included skull demographics if available and color photographs of orbits. A ray was added to the orbital photo using Adobe Photoshop, beginning at the anterior ethmoidal foramen and extending through the posterior ethmoidal foramen and optic canal. If the anterior-posterior ethmoidal ray (APER) entered the middle third of the optic canal it was described as “middle,” and if entering in the superior or inferior third of the canal, it was described as “superior” or “inferior” respectively. Skulls were excluded if there was significant damage to the orbits or wear precluding the ability to easily identify the anterior and posterior ethmoidal foramina and the optic canal.
A total of 5 skulls (10 orbits) were available for review. There were 5 male and 0 female skulls with an average age of 48 years (range, 24-69 years). The APER was considered in a middle position in three orbits, superior in five orbits, and inferior in two orbits.
The anterior and posterior ethmoidal foramina serve as critical landmarks often used when navigating towards the posterior orbit through a medial approach. Surgeons have been taught that a ray connecting these two points will lead directly to the center of optic canal. Although the APER can be a useful guide, its relationship with the optic canal varies considerably. Therefore surgeons should proceed with gentle dissection and caution when advancing towards the optic nerve using the APER alone.
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