 The optic nerve sheath diameter ONSD has been described as a highly sensitive 88-94 and specific 85 - 94 noninvasive technique of identifying increased intracranial pressures in patients with brain trauma, intracranial bleeding or stroke1-4. This method requires placement of an ultrasound probe on the patients closed eyelid and then a direct measurement of the diameter of the optic nerve sheath at a pre-specified distance from the globe. A value greater than 58 mm has been shown to correlate significantly with an increased ICP 20 cm H20; r 0.71, p0.001 5. 