A Novel Three-Dimensional Vector Analysis of Axial Globe Position in Thyroid Eye Disease

Purpose. To define a three-dimensional (3D) vector method to describe the axial globe position in thyroid eye disease (TED). Methods. CT data from 59 patients with TED were collected and 3D images were reconstructed. A reference coordinate system was established, and the coordinates of the corneal apex and the eyeball center were calculated to obtain the globe vector . The measurement reliability was evaluated. The parameters of were analyzed and compared with the results of two-dimensional (2D) CT measurement, Hertel exophthalmometry, and strabismus tests. Results. The reliability of measurement was excellent. The difference between and 2D CT measurement was significant (), and was more consistent with Hertel exophthalmometry than with 2D CT measurement (). There was no significant difference between and Hirschberg test, and a strong correlation was found between and synoptophore test. When one eye had a larger deviation angle than its fellow, its corneal apex shifted in the corresponding direction, but the shift of the eyeball center was not significant. The parameters of were almost perfectly consistent with the geometrical equation. Conclusions. The establishment of a 3D globe vector is feasible and reliable, and it could provide more information in the axial globe position.

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