Measurement of orbital volume by computed tomography: Especially on the growth of the orbit

Purpose: Using reconstructed x-ray computed tomography (CT) images of serial coronal sections, we measured the orbital volume and studied its changes with age. Methods: The subjects consisted of 109 patients (74 male, 35 female) 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 age, sex, weight, and inter-lateral orbital rim distance were examined. Results: The difference between two measurements in the same patient stood at 0.4% for measured volume, which showed good reproducibility of this measurement. The laterality in individuals stood at 0.06 cm(3); the difference was very small and no significant difference was found. Moreover, the orbital volume did not show any imbalance between the right and left eyes in any stage of growth. Both the height and the inter-lateral orbital rim distance had a strong correlation with the orbital volume. Conclusion: Referring to the relation between age and orbital volume, a strong correlation with an almost identical approximate equation was obtained for both sexes until the age of 12. Presumably, the rapid growth of the orbit comes to an end by 15 years of age in boys and by 11 years in girls. This means that more than 95% of the growth of the adult orbit has already been completed by the first half of the teens. The mean orbital adult Japanese is 23.6 +/- 2.0 cm(3) in men and 20.9 +/- 1.3 cm(3) in women. (C) 2001 Japanese Ophthalmological Society.