Proptosis- Causes, Correlation and Agreement Between Measurements of Hertel Exophthalmometer and Computed Tomography of Orbits

1. S.Kala Sumugam¹
2. Norlina Mohd Ramli¹
3. Zurina Zainal Abidin¹
4. Kartini Rahmat²

¹Department of Ophthalmology, University Malaya Medical Centre, Kuala Lumpur, Malaysia
²Department of Biomedical Imaging, University Malaya Medical Centre, Kuala Lumpur, Malaysia

Purpose: This observational study was designed to investigate the causes of proptosis in University Malaya Medical Centre, and to study the correlation and agreement between measurements of Hertel and computed tomography of orbit.

Methods: A total of 80 patients (40 normal patients, 40 patients with proptosis) were recruited in this study. Measurement was done with Hertel exophthalmometer and these patients also underwent computed tomography (CT) of orbits. The measurements were then repeated in the CT.

Results: The mean age of patients in non-proptosed group was 43.5 years. The mean age of proptosed patients was 39.33 years. The majority of patients with proptosis were diagnosed to have thyroid eye disease (55%). 59.1% of them are females.
The Hertel and CT measurements in non-proptosed and proptosed patients were strongly correlated (r=0.96 and r=0.93).

In the normal patients, the agreement between the CT and Hertel measurement was good with 95% limits of agreement within -0.70 to 1.78. However agreement was poorer in patients with proptosis with 95% limits of agreement of -2.36 to 3.33.

Conclusions: The most common cause of proptosis in this study is thyroid eye disease. Measurement using Hertel exophthalmometer and CT in both the proptosed and the normal group correlates and agrees well with each other.