Comparison of exophthalmos measurements: Hertel exophthalmometer versus orbital parameters in 2-dimensional computed tomography

Abstract

Objective: To compare the reliability of orbital parameters calculated using 2-dimensional computed tomography (CT) and Hertel exophthalmometry when measuring exophthalmos in normal subjects and in patients with thyroid-associated orbitopathy (TAO).

Design: Retrospective, observational case series.

Participants: CT images of 33 normal orbits and 69 orbits with TAO were included.

Methods: In central axial CT scans, globe area (GA), orbital area (OA), and GA/OA ratio were calculated by 2 observers using ImageJ. Interobserver agreement was analyzed for Hertel exophthalmometer and CT parameters. In patients with TAO, the association with activity and severity of TAO were also evaluated.

Results: GA and the GA/OA ratio measurements showed excellent interobserver agreement, whereas OA and the Hertel exophthalmometry measurements showed moderate agreement between the 2 observers. GA and the GA/OA ratio were significantly correlated with Hertel exophthalmometry measurements (r = -0.740, r = -0.706, respectively; all p < 0.001). GA and the GA/OA ratio were significantly correlated with the activity and severity of TAO (all p < 0.01).

Conclusions: GA and the GA/OA ratio were reliable CT parameters with a high intraclass correlation coefficient compared with Hertel exophthalmometer.