Abstract: Objective To explore the normal range of retrobulbar optic nerve sheath diameter(ONSD) measured by B mode ultrasonography in adults with normal intracranial pressure. Design Diagnostic technique evaluation. Participants 60 consecutive outpatients who underwent lumber puncture in Xuanwu Hospital，  from March 2012 to May 2013, and confirmed with normal intracranial pressure（70~200 mmH2O） and without any central nerve system disease, were enrolled. Methods Ultrasonographic ONSD at 3 mm behind the globe was measured by two different operators. The mean value of ONSDs measured by two operators was recorded as the patient’s ONSD value. We recorded the range of these ONSD values in adults with normal intracranial pressure, and analysis the consistency between two operators. Main Outcome Measures  Intracranial pressure, optic nerve sheath diameter. Results The ONSDs 3 mm behind eyeballs measured by B mode ultrasonography in adults with normal intracranial pressure were 5.38±0.67 mm (range: 3.9~7.4 mm) in right eyes, and 5.45±0.73 mm（range: 3.5~7.0 mm）in left eyes. No obvious difference was observed between right eyes and left eyes （t=-0.9, P=0.372）. The ONSDs of right eye in men were 5.62±0.62 mm and in women were 5.11±0.64 mm (t=3.129, P=0.003); the ONSDs of left eye in men were 5.73±0.63 mm and in women were 5.13±0.71 mm (t=3.460, P=0.001). There has significant differences between men and women. There is a good consistency between the two operators. Conclusion B mode ultrasonography is a simple and reliable method to detect the retrobulbar ONSD． There is a variation of ONSD in adults with normal intracranial pressure. (Ophthalmol CHN, 2014, 23: 347-350)

Key words:  ultrasonography, optic nerve sheath diameter, intracranial pressure