The orbit: A re-appraisal of the surgical landmarks of the medial and lateral walls.

The anterior ethmoidal foramen (AEF) and posterior ethmoidal foramina (AEF and PEF, respectively) on the medial wall and the cranio-orbital foramen (COF) on the lateral wall are used as landmarks in orbital surgeries. In surgery these foramina, the neurovascular structures they transmit and other orbital structures in close proximity need to be identified to minimise their risk of damage. Despite the clinical importance, the current understandings lack consistency in the precise location, microanatomy and morphology of the foramina. This study therefore aimed to document and analyze the microanatomy, location, and morphometric relations of the EF and COF to determine a standardized guideline to accessing the foramina. One hundred dry orbits were morphometrically analyzed, and a further six orbits were micro-dissected to determine the locations of the EF and COF. The orbital size dimensions were measured for each dry orbit and correlated with the morphometric distances. A complete morphometric and quantitative analysis showed the distances of the EF and COF to be variable, with greater variations observed in the incidence of the accessory EF and PEF distances in the medial wall, and in the presence of the COF and the accessory COF in the lateral orbital wall. Significant correlations were observed between the length of the medial orbital wall and some EF distances. This study is the first to suggest a standardized method of locating these foramina in the orbit irrespective of population and sex differences, in order to help improve clinical applications in crucial orbital surgeries. Clin. Anat. 29:998-1010, 2016.