Aim: To provide age and gender-specific reference values for orbital fat and muscle volumes (MV) in Caucasian adults.
Patients and methods: Computed tomographic scans of 160 orbits from 52 men and 55 women, aged 20-80 years, not affected by orbital disease were evaluated. Orbital bony cavity volume (OV), fat volume (FV) and MV were calculated by a previously validated method using the software program Mimics. Ratios of FV to OV and of MV to OV were determined.
Results: OV, FV and MV were all significantly larger in men than in women (p<0.001), but FV/OV and MV/OV were similar in both sexes. OV and MV did not change with age, but FV increased with advancing age in both women (p<0.001) and men (p<0.001). Linear regression analysis with FV/OV and MV/OV ratios as dependent variables and age and gender as independent variables showed a significant correlation between age and FV/OV (r=0.52, p<0.0001) and age and MV/OV (r=-0.26, p=0.001).
Conclusions: Advancing age is associated with an increase of FV/OV and a minor decrease of MV/OV. Gender-specific differences in orbital FV and MV disappear once FV and MV are related to OV, by calculating the ratios FV/OV and MV/OV. Age-specific gender-neutral reference ranges (2.5 and 97.5 percentiles) of FV/OV and MV/OV are presented.