Article Figures & Data
Figures
- Fig 1.
A and B, Axial CT scans (bone window on left, soft tissue window on right) showing the orbital apex point indicated by the curved arrow (A) and the orbital rim angle (B). A, The apex point is defined as the anterolateral border of the groove in the sphenoid body formed by the intracavernous portion of the internal carotid artery (labeled 2) on the section just inferior to the anterior clinoid process. B, The orbital rim angle (43°) is measured at the level of the medial palpebral ligament (arrow). C−E, The same axial section containing the bulk of the medial and lateral rectus muscles shows the medial wall angle (C), the lateral wall angle (D), and the orbital apex angle (E). For the medial and lateral walls, the angle that best describes the widest bony point of the orbital wall around the muscular bellies is recorded. The angular change is recorded as positive if the resultant angle is wider than the orbital rim angle, and negative for narrower angles. F, The length of the lateral orbital wall is measured on the section just inferior to the anterior clinoid.
- Fig 2.
Axial section at midglobe level showing the interzygomatic line (labeled 11) and maximum horizontal diameters of the right medial and lateral rectus muscles (measurements labeled 4 and 3, respectively). The distance from the midpoint of the maximum muscular diameter of the medial (measurement 8) and lateral rectus muscles (measurement 7) to the interzygomatic line is also recorded. Proptosis of the left globe relative to the interzygomatic line is labeled as measurement 6. Left optic nerve stretch (labeled 13) is measured from the retrobulbar optic nerve to the orbital apex point (labeled 1).
- Fig 3.
Scatterplots of the MDI and orbital apex angle (A), MDI and medial wall angle (B), and MDI and lateral wall angle (C) in patients with and without ON. Greater muscular enlargement is accompanied by wider orbital angles with or without (w/o) ON. For identical MDI and orbital angles, the orbital angles are narrower and MDI greater in patients with ON, respectively. Within the borderline MDI range of 22–30 mm in B, 15 of 26 patients with zero or negative medial angles (57.7%) had ON (P = .07), compared with 1 of 6 patients with positive medial angles (16.7%).
- Fig 4.
Scatterplot depicting the relationship between lengths of lateral orbital wall and orbital rim angles in patients with and without (w/o) ON.
Tables
- Table 1:
Demographics, quantitative CT measurements, and categoric variables in patients with Graves ophthalmopathy, with and without ON*
Graves Ophthalmopathy ON Without ON P Value Demographics No. orbits 32 50 Age 55.9 ± 11.5 (39–78) 44.7 ± 11.0 (28–65) Sex (male, female) 14 M, 18 F 20 M, 30 F Bony confines Bony orbital angle (degrees) Orbital rim 42.4 ± 2.5 (39–49) 42.2 ± 2.4 (37–51) <.727 Medial wall -0.1 ± 5.7 (−8–12) −3.6 ± 5.2 (−13–12) <.006 Lateral wall 6.7 ± 3.0 (1–13) 4.7 ± 2.5 (1–11) <.002 Total angular change 6.6 ± 7.5 (−3–20) 1.1 ± 6.5 (−8–17) <.001 Orbital apex 49.0 ± 8.2 (38–65) 43.3 ± 7.4 (30–59) <.002 Length of lateral wall (mm) 44.1 ± 2.9 (35.7–48.9) 42.5 ± 3.2 (33.7–47.5) <.022 Extraoccular muscles (mm) Maximum muscle diameter Medial rectus 7.2 ± 1.8 (3.8–10.5) 4.8 ± 1.8 (2.6–10.0) <.0005 Lateral rectus 4.9 ± 1.5 (2.3–8.2) 3.8 ± 0.9 (2.1–6.4) <.0005 Superior muscle group 6.5 ± 1.8 (3.6–9.5) 4.9 ± 1.7 (2.6–8.7) <.0005 Inferior rectus 7.1 ± 2.0 (3.2–12.8) 5.0 ± 1.6 (2.6–9.5) <.0005 Superior oblique 3.0 ± 0.7 (1.8–4.5) 2.8 ± 0.7 (1.8–4.4) .212 MDI 29.0 ± 5.2 (21.1–42.3) 21.2 ± 4.8 (14.3–32.3) <.0005 Medial rectus bulk from IZ line 14.0 ± 3.9 (5.4–21.0) 12.3 ± 3.4 (6.0–21.2) .049 Lateral rectus bulk from IZ line 16.0 ± 3.0 (10.8–21.2) 14.8 ± 2.8 (10.7–21.1) .084 Neurovascular structures Proptosis from IZ line 2.6 ± 2.7 (−3.5–7.0) 3.5 ± 4.0 (−4.6- 12.7) .200 Optic nerve stretch 40.8 ± 3.2 (35.0–47.9) 39.7 ± 4.1 (30.7–46.6) .243 Optic nerve sheath Retrobulbar 5.7 ± 0.7 (4.2–7.2) 5.8 ± 0.9 (4.0–8.1) .464 Waist 3.7 ± 0.6 (2.4–5.2) 3.6 ± 0.7 (1.6–5.5) .703 Superior ophthalmic vein 1.9 ± 0.4 (1.2–2.7) 1.8 ± 0.4 (1.2–2.9) .273 Apical crowding 3 (1–3) 1 (0–3) <.0005† Presence of intracranial fat prolapse 11 (34.4%) 13 (26.0%) .416‡ Note:—IZ line indicates interzygomatic line; ON, optic neuropathy; MDI, muscle diameter index.
* Descriptive statistics presented are mean ± SD (range) and count (%) for the presence of intracranial fat prolapse. All mean quantitative CT measurements between the 2 groups are compared using the Student 2-tailed t test. Statistical significance is defined at P < .05.
† The categoric variables are compared using the Mann-Whitney U test. Statistical significance is defined at P < .05.
‡ The categoric variables are compared using the χ2 square test. Statistical significance is defined at P < .05.
Bony Structure Measurement Bony orbital angle (degrees) Orbital rim 42.5 ± 2.5 (39–47) Medial wall −4.6 ± 1.9 (−7 to −1) Lateral wall 4.9 ± 2.5 (1–10) Total angular change 0.3 ± 2.9 (−5–5) Orbital apex 42.8 ± 4.2 (35–52) Length of lateral wall (mm) 42.7 ± 1.9 (39.4–45.9) - Table 3:
Sensitivity, specificity, and positive and negative predictive values of using MDI alone versus MDI in combination with medial and lateral orbital angles in predicting ON in Graves ophthalmopathy
Percentage MDI Alone MDI and Medial and Lateral Wall Angles Sensitivity 60.0 (18/30) 73.3 (22/30) Specificity 86.0 (43/50) 90.0 (45/50) Positive predictive value 72.0 (18/25) 81.5 (22/27) Negative predictive value 78.2 (43/55) 84.9 (45/53)
