RF35 | PSAT262 Comparative Study of Hertel Exophthalmometer and Luedde Exophthalmometer Versus Computed Tomography for Measurement of Proptosis in Normal Subjects

BACKGROUND: Clinical evaluation of proptosis is measured by an exophthalmometer. Hertel exophthalmometer has long been considered a standard instrument for measurement of eye protrusion. The reading may be subject to error while the examiners read through the integral reflection mirrors. Luedde exophthalmometer, which is a ruler correcting for parallax, is easier to use and less expensive than Hertel exophthalmometer. Since CT scan of orbits or brain provides the most objective assessment of proptosis measurements, we aim to study the correlation between Luedde and Hertel exophthalmometers in comparison with the CT scan for the evaluation of proptosis in normal subjects. METHODS: This prospective study was carried out between November 2020 and January 2021. Sixty-three patients were enrolled from a single tertiary hospital. All patients underwent CT scan of brain for medical reasons. On the same day, proptosis was measured with Hertel and Dual Luedde exophthalmometer by two independent examiners. Measurement of proptosis from CT scan was performed by one experienced neuroradiologist, using 2 reference measurement techniques. Correlation coefficients between proptosis values measured by each exophthalmometer and CT scan were compared. RESULTS: The mean age of the participants was 63 years old and 54% were female. For the right eye, mean proptosis measurement was 14.9+/-1.6 mm by Hertel exophthalmometer, 14.1+/-2.3mm by Luedde exophthalmometer, 16.6+/-2.3 mm by first CT technique, and 13.1 +/- 2.2 mm by second CT technique. For the left eye, mean proptosis measurement was 15.5 +/-1.5mm by Hertel exophthalmometer, 13.7+/-2.3 mm by Luedde exophthalmometer, 16.6+/-2.3 mm by first CT technique and 13.1 +/- 2.2 mm by second CT technique. The Intraclass correlation coefficient (ICC) of Hertel exophthalmometer for proptosis measurement compared to first CT technique and second CT technique were 0.63 and 0.60 for right eye; 0.61 and 0.55 for left eye, respectively. The ICC of Luedde exophthalmometer for proptosis measurement compared to first CT technique and second CT technique were 0.78 and 0.74 for right eye; 0.77 and 0.74 for left eye, respectively. CONCLUSION: There is a good correlation between Hertel and Luedde exophthalmometers in evaluation of proptosis. However, proptosis measured by Luedde exophthalmometer shows superior correlation with CT scan. The result suggests that Luedde exophthalmometer can be routinely used for measurement of proptosis in place of Hertel exophthalmometer, given the simplicity and the inexpensiveness of the instrument. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 12:30 p.m. - 12:35 p.m.