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Table 1 Optic nerve sheath, eyeball, and optic canal anterior (orbital) opening CT measurements (in mm)

From: Quantitative relations between the eyeball, the optic nerve, and the optic canal important for intracranial pressure monitoring

Distance/position Right eye Left eye
  Mean ± SD Max Min Mean ± SD Max Min
Distal ONSD* 4.94 ± 1.51 7.5 3.5 5.17 ± 1.34 7.9 3.8
Middle ONSD** 4.35 ± 0.76 7.6 3.3 4.45 ± 0.62 5.9 3.3
Proximal ONSD*** 3.84 ± 0.82 5.2 2.7 3.65 ± 0.70 4.8 2.9
Proximal ONS area 11.58 ± 1.8 21.23 5.7 10.46 ± 1.5 18 6.6
Transverse 22.822 ± 1.7 25.5 20.0 22.936 ± 1.8 25.8 19.4
Eyeball diameter
Optic canal anterior opening
Longer diameter 4.8 ± 1.8 5.8 3.5 5.0 ± 1.8 5.8 3.6
Shorter diameter 4.2 ± 1.6 4.8 2.9 4.2 ± 1.7 4.8 2.8
Area (mm2) 15.83 ± 2.3 19 7.2 16.49 ± 2.7 21.86 7.9
  1. *3 mm behind the globe.
  2. **10 mm behind the globe.
  3. ***3 mm before entering the anterior opening of the optic canal.