Computed Tomography Exophthalmometry

Exophthalmometry is an important clinical tool used in evaluating many orbital diseases. The authors evaluated whether or not exophthalmometry readings obtained from computed tomography (CT) correlate with traditional Hertel measurements. Patients with orbital disease who had undergone clinical and CT examination were identified, and CT exophthalmometry readings were obtained digitally using a GE PACS radiograph viewing system in 53 orbits (44 thyroid-associated ophthalmopathy and 9 post-trauma). Exophthalmometry data obtained with CT were compared with Hertel readings obtained by an experienced examiner. CT data and clinical data were obtained by separate and masked observers. 46 of 53 CT exophthalmometry measurements were within 2 mm of the value recorded from Hertel testing. The CT metrics, on average, provided exophthalmometry that was 0.03 mm shorter than Hertel (95% CI). The intraclass correlation coefficient was 0.95 (95% CI) for the two forms of measurement. The authors conclude that CT exophthalmometry correlates well with Hertel exophthalmometry.