Diagnostic Accuracy of the Optic Nerve Deformability Index and Optic Nerve Sheath Diameter as a Noninvasive Predictor of Intracranial Pressure

Inclusion Criteria: * age 18 to 65 years * increased ICP (e.g., TBI, sub arachnoid hemorrhage, intracranial hemorrhage) * a Glasgow Coma scale=3-12 and requiring ICP monitoring via invasive methods (e.g. extra ventricular drain, lumber drain) Exclusion Criteria: * chronic hydrocephalus * extensive local orbit trauma * a pre-existing ocular disease affecting the optic nerve and/or orbital cavity * hyperthyroidism with exophthalmia * facial trauma affecting the orbits and/or eyeballs * optic nerve trauma * signs of critically raised ICP, needing urgent surgery. * hemodynamically unstable between ONSD acquisition and ICP measurement. * receiving medication that would decrease ICP between ultrasound imaging and ICP measurement, i.e. mannitol, hypertonic saline or steroids.