Elsevier

Japanese Journal of Ophthalmology

Volume 45, Issue 6, November–December 2001, Pages 600-606
Japanese Journal of Ophthalmology

Laboratory investigation
Measurement of Orbital Volume by Computed Tomography: Especially on the Growth of the Orbit

https://doi.org/10.1016/S0021-5155(01)00419-1Get rights and content

Abstract

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 interlateral 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 cm3; 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 interlateral 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 volume in adult Japanese is 23.6 ± 2.0 cm3 in men and 20.9 ± 1.3 cm3 in women.

Introduction

Not only changes in the limited volume of tissue in the orbit, but also changes in the shape and size of the orbit, cause exophthalmos and enophthalmos.1, 2, 3 Oono4 studied the orbital volume of Japanese by actual anatomical measurement and reported it to be 26.0 cm3 and 25.9 cm3 for the right and left eyes in men and 23.1 cm3 and 23.2 cm3 in women. A figure between 25 cm3 and 30 cm3 is widely accepted. As is generally known, the orbital volume varies with race and sex.5

Attempts at measuring the orbital volume by x-ray computed tomography (CT) have been made for a long time, but results of these studies have yet to be utilized clinically.1, 6, 7 There has as yet been no report on the growth of orbital volume. Actual in vivo measurement, radiographs, and x-ray CT have been used merely as a method of one-dimensional measurement. So a great deal was expected of clinically applicable methods to measure the orbital volume and studies of basic data.8, 9, 10, 11

Using reconstructed x-ray CT images of serial coronal sections, we measured the orbital volume and studied its changes with aging. The results made it clear that a more reliable measurement of orbital volume can be made by this method. Additionally, we studied the relation between the orbital volume and age by comparing parameters that can easily be obtained in the clinical practice of ophthalmology. This article is a report of our findings.

Section snippets

Subjects

The subjects were represented by 129 radiographs from 109 patients (74 male, 35 female) who had undergone x-ray CT for the orbit mainly because of injury and whose orbit was normal on one side. There are few cases of injury in infants and not enough cases are available. So cases not likely to affect the growth of the orbit on the normal side, such as a case of retinoblastoma involving one eye, were added to the subjects. CT was performed twice at intervals of about 2 weeks after surgery on a

Reproducibility of Orbital Volume and Laterality

Table 1 represents the results of measurements of the orbital volume on the normal side before and after surgery in the fracture group, and the orbital volume on both sides in the normal group. The difference between the two measurements in the fracture group stood at 0.09 ± 0.69 (mean value ± SD) cm3 and no significant difference was found, which showed the reproducibility of this measurement to be good. The laterality in the normal group stood at 0.06 ± 0.56 (mean value ± SD) cm3; the

Discussion

Studies on the orbital volume using CT images have been reported since the mid-1980s, and the diagnostic and clinical usefulness of the data obtained has been recognized. However, most of the reports dealt with eyes with a blowout fracture of the orbit or thyroid ophthalmopathy,13, 14 and studies on the normal orbit are few.6 With the measurement of orbital volume using sections of CT images, the extent of measurement anterior to the orbit differs from one section to another according to the

Conclusions

  • 1.

    Using x-ray CT images of 109 cases, 129 examinations, we measured the volume of the normal orbit and charted its growth.

  • 2.

    Serial coronal sections in 2-mm thick slices ranging from the lacrimal fossa to the optic canal were used in the measurement of orbital volume.

  • 3.

    The reproducibility of the measurements was good.

  • 4.

    No laterality of the orbital volume was found.

  • 5.

    Orbital volume strongly correlated with height and interlateral orbital rim distance, suggesting the possibility that orbital volume can be

Acknowledgements

This paper was published in Japanese in the Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 2000;104:724–30. It appears here in a modified form after peer review and editing for the Japanese Journal of Ophthalmology.

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