AN EXPERIMENTAL INVESTIGATION OF THE SAFE DISTANCE FOR INTERNAL ORBITAL DISSECTION

Purpose: The purpose of this investigation was to determine the distan ce from the orbital rim to the important soft tissues of the orbital a pex using eight reference points to provide clinically useful informat ion for surgical decision making. Materials and Methods: Eight human c adavers were used in this investigation. After circumorbital incisions were made and the canthal Ligaments were detached, a careful subperio steal dissection was performed to the soft tissues of the orbital apex . Four reference lines were established. The first two were based on a horizontal line drawn through the medial and lateral canthal ligament s and a perpendicular to this through the infraorbital foramen. The ot her two were created at points 45 degrees from the first two. Depth me asurements were made with a straight probe at the eight points where t he lines crossed the orbital rim. Means, standard deviations, and rang es were derived, and statistical differences were calculated between r ight and left orbits using a paired-samples t-test. Because no right a nd left differences were noted (P < .05), the data were pooled. Result s: The mean distance from the orbital rim to the soft tissues of the o rbital apex was 44.1 +/- 1.4 mm medially, 38.3 +/- 3.0 mm laterally, 4 4.5 +/- 1.72 superiorly, and 39.4 +/- 2.9 mm inferiorly. The superomed ial distance was 46.3 +/- 2.7 mm, the inferomedial distance was 44.1 /- 1.4 mm, the inferolateral distance was 41.4 +/- 2.5 mm, and superol ateral distance was 39.4 +/- 2.8 mm. Conclusions: The distances from t he orbital rim to the soft tissues of the orbital apex varied among th e eight different reference points (range, 38.3 +/- 3.0 mm to 46.3 +/- 2.7 mm). No distance was less than 31.0 mm or exceeded 51.1 mm. There was no difference noted (P < .05) between the right and left sides fo r each of the corresponding reference points.