Normative measurements of orbital structures using MRI

J Comput Assist Tomogr. May-Jun 2000;24(3):493-6. doi: 10.1097/00004728-200005000-00025.

Abstract

Purpose: The purpose of this work was to establish criteria for the diameters of normal extraocular muscles and superior ophthalmic vein and width of the optic nerve-sheath complex, to determine normal globe position as seen on MRI, and to investigate the effects of age and sex on these structures.

Method: Diameters of the extraocular muscles and superior ophthalmic vein, width of the optic nerve-sheath complex, and distance from the interzygomatic line to the posterior margin of the globe were calculated for 200 normal orbits of 100 patients on T1-weighted MR scans.

Results: Normal ranges for diameters of the extraocular muscles were as follows (mean +/- 2 SD): medial rectus, 3.2-4.9 mm; lateral rectus, 2.6-4.8 mm; inferior rectus, 3.7-6.0 mm; superior group, 3.1-5.6 mm; superior oblique, 2.4-4.1 mm. The normal position of the posterior pole of the globe was 8.9 mm behind the interzygomatic line (range 5.0-12.7 mm). The mean diameters of the extraocular muscles in male patients were significantly larger than those in female patients (p < 0.001).

Conclusion: These data may be of value in quantitatively evaluating MRI of the orbit.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Female
  • Humans
  • Magnetic Resonance Imaging*
  • Male
  • Middle Aged
  • Oculomotor Muscles / anatomy & histology
  • Optic Nerve / anatomy & histology
  • Orbit / anatomy & histology*
  • Prospective Studies
  • Reference Values