Longitudinal Changes in Adult Bony Orbital Volume.

Abstract

To our knowledge, no prior study has measured bony orbital volume in a group of subjects over time. This study evaluates longitudinal changes in bony orbital volume with age. A search was created for patients with digitized CT imaging studies of the orbit at least 8 years apart. Charts with a history of prior head trauma, head and neck tumors, sinus disease, head surgery, elevated intracranial pressure, thyroid eye disease, or conditions that could affect bone metabolism were excluded. Three outcome measures were used: orbital volume, medial orbital wall length, and lateral orbital wall length. Categorical data were summarized with frequency (%); normally distributed continuous data are summarized with mean (standard deviation), and non-normally distributed data were summarized with median. Normality was verified with Shapiro-Wilk Test. Paired t-tests were used to analyze the differences in the 3 outcome variables. One hundred and eighty-two subjects, 91 males and 91 females, were included. The median time between CT scans was 9.4 years. Orbital volume was significantly larger at the second scan than the first (p < 0.001). The average difference in orbital volume was 0.91 ml, an increase of 4.1%. Lateral orbital length was significantly shorter in the second scan than in the first (p = 0.046) though the difference was only 0.4 mm. There was no statistically significant change in medial orbital wall length. Bony orbital volume increases in individuals with age. This increase in orbital volume occurs in the context of soft tissue changes to contribute to the aging appearance of the periorbital region.