Volume measurements of normal orbital structures by computed tomographic analysis

Area of Science:

• Ophthalmology
• Radiology
• Anatomy

Background:

• Accurate volumetric measurements of orbital structures are crucial for diagnosing various orbital diseases.
• Previous methods for determining orbital volumes have limitations in precision and in vivo application.

Purpose of the Study:

• To establish normative volumetric data for normal orbital soft tissues, extraocular muscle, orbital fat, and bony orbit in adults.
• To validate the accuracy of computed tomographic (CT) digital data and computer graphic analysis for these measurements.

Main Methods:

• Utilized computed tomographic (CT) digital data and off-line computer graphic analysis.
• Measured volumes of orbital soft tissue, extraocular muscle, orbital fat, and bony orbit in vivo in 29 patients (58 orbits).
• Validated technique accuracy using physical and simulated silicone orbit phantoms (7%-8% accuracy).

Main Results:

• Determined upper limits of normal for adult bony orbit (30.1 cm³), soft tissue (20.0 cm³), orbital fat (14.4 cm³), and muscle (6.5 cm³).
• Observed minor volume differences between sexes but minimal differences between right and left orbits within individuals.
• Established mean values and upper limits for adult orbital structures.

Conclusions:

• The study provides reliable in vivo volumetric data for normal adult orbital structures.
• These normative values serve as a critical reference for future studies and clinical assessments of orbital abnormalities.
• The CT-based method offers an accurate approach for quantifying orbital volumes.