Three-dimensional characterisation of the globe position in the orbit.

PURPOSE

Current methods to analyse the globe position, including Hertel exophthalmometry and computed tomography (CT), are limited to the axial plane and require the lateral orbital rim and cornea as landmarks. This pilot study aimed to design a method to measure the position of the globe in the axial, coronal and sagittal plane and independent from orbital bony and corneal references.

METHODS

With the aid of three-dimensional CT reconstruction technology, we determined the globe position in the orbit based on the centre of the globe. Method validation was performed using data of consecutive orbital CT scans from the control group and from the patients with Graves' orbitopathy who underwent orbital decompression surgery with removal of the lateral orbital margin.

RESULTS

The inter- and intra-observer reliability was excellent with a high intraclass correlation coefficient (> 0.99, 95% CI [0.97; 1.00]). In the decompressed orbits, there was a statistically significant globe position shift along the anterior-posterior axis (P = 0.0005, 95% CI [0.63; 3.66]), but not along the medial-lateral and superior-inferior axis.

CONCLUSION

The 3D CT method can accurately and reliably characterise the globe position shift in the three dimensions without using orbital and corneal anatomical landmarks. The method can be useful to determine the globe shift in proptosis, enophthalmos, hypoglobus and hyperglobus, even in the presence of strabismus and orbital bone defects.