Comparability of proptosis measurements by different techniques

Area of Science:

• Ophthalmology
• Endocrinology
• Radiology

Background:

• Graves' ophthalmopathy causes proptosis, requiring accurate measurement for treatment assessment.
• Clinical measurements of proptosis can be variable.
• Computed tomography (CT) offers an alternative imaging method.

Purpose of the Study:

• To compare proptosis measurements obtained by clinicians versus computed tomography (CT).

Main Methods:

• Prospective randomized study of orbital radiotherapy for Graves' ophthalmopathy.
• Proptosis measured by clinicians (exophthalmometer) and CT scans.
• CT scans used head fixation to minimize positional artifact.

Main Results:

• Clinical measurements were consistently higher (0.6–1.6 mm) than CT measurements.
• Discrepancy partly due to measuring anterior vs. posterior corneal surface.
• Significant variability (up to 5 mm) observed between different clinicians' single measurements.

Conclusions:

• Clinical proptosis measurement reproducibility is crucial for Graves' ophthalmopathy therapeutic studies.
• Systematic differences between CT and clinical proptosis measurements exist.
• Standardized measurement techniques are important for comparing clinical trial results.