Hertel exophthalmometer versus computed tomography scan in proptosis estimation in thyroid-associated orbitopathy

Area of Science:

• Ophthalmology
• Radiology
• Endocrinology

Background:

• Thyroid-associated orbitopathy (TAO) frequently causes proptosis.
• Accurate measurement of proptosis is crucial for TAO management.
• Hertel exophthalmometry is a common clinical method, but its accuracy can be limited.

Purpose of the Study:

• To compare proptosis measurements obtained by Hertel exophthalmometry with those from three computed tomography (CT) scan methods.
• To evaluate the effectiveness of different CT approaches, including a novel method, in assessing proptosis.

Main Methods:

• Retrospective analysis of 133 patients with TAO.
• Proptosis measured by two independent observers using Hertel exophthalmometry.
• Three CT scan methods were employed: Method 1 (axial plane, lateral rims-cornea), Method 2 (axial plane, medial-lateral rims-cornea), and Method 3 (sagittal plane, superior-inferior rims-cornea).
• Correlation analysis was performed, with patients grouped by inter-eye proptosis differences (≤2 mm vs. >2 mm).

Main Results:

• All three CT methods demonstrated statistically significant correlations with Hertel exophthalmometry (Pearson's r ranging from 0.623 to 0.727).
• For patients with inter-eye proptosis differences greater than 2 mm, correlations were r=0.495 (CT Method 1), r=0.634 (CT Method 2), and r=0.635 (CT Method 3).
• CT Methods 2 and 3 showed significant relationships with Hertel values in cases with larger proptosis asymmetry.

Conclusions:

• Computed tomography offers a statistically significant correlation with Hertel exophthalmometry for proptosis measurement in TAO.
• CT Methods 2 and 3, particularly the new additive method (Method 3), show promise for accurately assessing proptosis, especially in patients with significant inter-eye differences (>2 mm).
• These CT methods may provide a valuable adjunct or alternative to traditional exophthalmometry in complex TAO cases.