[Measurement of orbital volume by computed tomography--especially on the growth of orbit]

Using reconstructed X-ray computed tomography (CT) images of serial coronal sections, we measured the orbital volume and studied its changes with age.

The subjects consisted of 109 patients (74 males, 35 females) who had undergone X-ray CT. After the reproducibility of orbital volume measurements and laterality in individuals were confirmed, the relation between the orbital volume and the age, sex, weight, and interlateral orbital rim distance were examined.

The difference between two measurements in the same patients was 0.4% for measured volume, which showed the reproducibility of this measurement to be good. The laterality in individuals was 0.06 cm3; this difference was very small and not significant. The orbital volume showed no unbalance between the right and left at any stage of growth. Both the height and the interlateral orbital rim distance had a strong correlation with the orbital volume. Referring to the relation between age and orbital volume, a strong correlation with an almost identical approximate equation was obtained for both sexes under 12 years of age. Presumably, the rapid growth of the orbit comes to an end by 15 years of age in males and 11 years in females. This means that more than 95% growth of adults has already been completed in the first half of the teens. The mean orbital volume in adult Japanese is 23.6 +/- 2.0(mean +/- standard deviation)cm3 in males and 20.9 +/- 1.3 cm3 in females.