The Effect of Pneumoperitoneum on Intracranial Pressure in Pediatric Laparoscopic Surgery: Ultrasonographic Measurement of Optic Nerve Sheath Diameter

A thick layer of gel is applied on the upper closed eyelid. The linear 13- to 6-MHz ultrasound probe is then placed in the gel, without exerting pressure on the eye. Two measurements are taken for each optic nerve: one in the transverse plane, with the probe being horizontal, and one in the sagittal plane, with the probe being vertical. The final ONSD is the mean of these measurements.