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J.P. S. Garcia, P.M. T. Garcia, P.T. Finger; An Automated Technique of Optic Nerve Measurement by 3D Ultrasound Tomography . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2394.
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Purpose:In place of expensive tests like CT scan and MRI, coronal scans by three–dimensional ultrasonography may be a simpler alternative for measuring the optic nerve diameter in human eyes. Using the profile line measurement technique of the 3D–Ultrasound Tomography System (3DUS), the range of optic nerve sheath diameter (ONSD) in normal volunteers was found to be consistent with the 4–6 mm normative range established by CT scan. The i–scan 1000 Ultrasound Tomography System, which has recently become available, is equipped with an automated software program for measuring the average optic nerve diameter. This modality may subsequently be used for screening patients with acute intracranial hypertension. Our purpose is to determine if the new automated technique can be used to measure the average optic nerve diameter in normal human eyes. Methods:Using 3D–image volume files of the optic nerve, coronal sections were chosen 3mm behind the globe. With the new automated technique for optic nerve measurements (proprietary software program courtesy of Justin Pedro, OTI–Canada), average values were automatically generated by tracing the circumference of the nerve on the computer screen. Data were analyzed using Excel and GraphPad Prism 3.03 (Microsoft, Seattle, WA). Results:Twenty three normal optic nerve 3D–ultrasound files from 22 healthy volunteers (14 males, 8 females) were retrospectively reviewed. Age ranged from 24 to 68 years. The average ONSD was found to be 5.6 mm (range: 4.8 to 6) SD 0.4 mm. These values were the same regardless of sex. The average ONSD was 5.5 mm in subjects younger than 50 years, and 5.6 mm SD 0.4 mm in subjects 50 and older. Conclusions:The new automated technique by 3D–ultrasound tomography is a fast and simple means to obtain average optic nerve measurements in vivo. Our range of 4.8 to 6 mm is consistent with published normative data on ONSD by CT scan. A larger scale prospective study on normal eyes utilizing this automated technique will be needed to validate our findings.
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