Ocular sonography is a fast, simple, and non-invasive tool to detect elevated intracranial pressure (ICP) by measuring the optic nerve sheath diameter (ONSD). Several studies have shown a positive correlation between increased ONSD (>5.7mm) and elevated ICP (>20mmHg). Although ultrasound may not replace CT or MRI to diagnose the cause of the increased ICP, its use as a triage tool can expedite these tests.
The technique:
Use linear probe on closed eyelid.
Identify the optic nerve sheath.
Measure the optic nerve sheath, 3mm behind globe.
Rotate probe 90 degrees and measure again.
Average both diameters.
Please see the references below for more information and, as with any new technique please consult local experts prior to making clinical decisions.
References
http://www.sonoguide.com/smparts_ocular.html
Soldatos, T. et al. Optic nerve sonography in the diagnostic evaluation of adult brain injury. Crit Care. 2008; 12(3): R67. Epub 2008 May 13.
