Investigation of the Orbital Arterial Distribution Using Image Superimposition to Determine Safe Zones for Retrobulbar Injection and to Prevent Filler Complications

Retrobulbar filler injection has recently been considered an ideal method for orbital volume enhancement due to its nontoxic, easily reversible, and noninvasive characteristics. This study determined the arterial distribution in the orbit with the aim of defining a safety zone for retrobulbar filler injections used to enhance the orbital volume.Twenty-seven orbits of 24 formalin-embalmed cadavers were dissected. The orbital arteries were identified after removal of the eyeball, extraocular muscles, and connective tissues. The course of each orbital artery was then recorded in each specimen, and all of the courses were then superimposed to determine the arterial distribution in the orbit.The superimposition of lined images based on the orbital vasculature of each specimen revealed that the arterial density was highest in the superonasal region and lowest in the inferotemporal region. In particular, orbital arteries were scarce at 8 o'clock and 4 o'clock in the right and left orbits, respectively, and an artery-free zone was demonstrated in the outer part of those directions.When performing a transcutaneous retrobulbar injection of filler for orbital volume enhancement, the relative safety zone could be considered to be located at 8 o'clock and 4 o'clock in the right and left orbits, respectively. The detailed topographic information about the arterial distribution in the orbit, provided by the present study, may help oculofacial surgeons to avoid injury to major vessels and decrease the risk of retrobulbar hemorrhage and vision-threatening complications.