CT definition of the surgical apex in the orbit

Abstract

The orbital apex is an undefined but well understood concept of Orbital Surgeons. We sought to determine the surgical apex area specifically where the volume ratio decreases significantly impacting on the optic nerve. A retrospective analysis using PACS program processing, measured the right retrobulbar space volume changes in 100 randomly selected cases without orbital pathology where CT was performed for non-ophthalmic indications. Volume of the retrobulbar space was measured between two recognizable landmarks. The first landmark being the point of exit of the optic nerve from the eye and the second landmark the optic nerve's point of exit from the orbit. The measured length between these two points was divided into five equal segments, V1-V5. The volumes of all 5 segments were compared and the most significant area of volume depletion was established. The mean numeric value of measured orbital volumes was compared. A ratio difference of V1/V2 was less than 2, V2/V3 was 2.32 (± 0.27), V3/4 was 3.24 (± 0.39), and V4/V5 was 5.67 (± 1.66). The most remarkable difference in ratio was between V4 and V5 (mean 5.67 ± 1.66 with p < .0001). The V3 segment (the posterior 3/5 of the retrobulbar space volume) is the location where decrease in orbital volume impacts, and measured ratios are statistically significant. We defined the surgical apex as the posterior 3/5 of the retro-bulbar orbital space. It is consequently the area of higher risk for optic nerve compression. This definition could be routinely utilized by ophthalmologists and neuroradiologists when evaluating masses affecting the orbit.

Clinical and radiological characteristics of odontogenic orbital cellulitis

“…In particular, the proximity of this portion of the inferior orbital ssure to the orbital apex can place patients at greater risk of visual impairment. The spread of odontogenic orbital cellulitis to the surgical orbital apex, de ned as the posterior 3/5 of the retrobulbar orbital space, makes for a vision-threatening condition [27] . Infectious spread to this region presents higher risk of optic nerve decompression due to the most signi cant decrease in volume, attesting to the important of early recognition of clinical and radiological signs.…”

Objective analysis of facial bone fracture CT images using curvature measurement in a surface mesh model

“…Facial bone is composed of a collection of thin segments and contains hollow structures (i.e., foramens and sinuses), which distinguishes it from long bones. Because of this difference, analysis software is an essential component for facial bone studies and image assessment 4,15 . Therefore, clinical physicians familiar with facial bone images and computer scientists who can develop image analysis software conducted a joint study.…”

“…However, facial bones are difficult to evaluate using biomechanical studies such as applying impact or weight loading. Thus, to visualize facial fractures, computed tomography (CT) studies are performed before and after surgery 4 . These studies provide useful information to determine whether the fracture site has been adequately reduced.…”

Objective Analysis of Facial Bone Computed Tomography Images Using Curvature Measurement

“…Facial bone is composed of a collection of thin segments and contains hollow structures (i.e., foramens and sinuses), which distinguishes it from long bones. Because of this difference, analysis software is an essential component for facial bone studies and image assessment 4,10 . Therefore, clinical physicians with experience with facial bone images and computer scientists who can develop image analysis software conducted a joint study.…”

“…However, facial bones are di cult to evaluate using biomechanical studies such as applying impact or weight loading. Thus, to visualize facial fractures, computed tomography (CT) studies are performed before and after surgery 4 . These studies provide useful information to determine whether the fracture site has been adequately reduced.…”