Ultrasound assessment of optic nerve sheath diameter (ONSD) has been proposed as a non-invasive means of intracranial pressure (ICP) determination for over 20 years 1 . More recently, literature is emerging that increasingly confirms its correlation to standard invasive intracranial monitoring in order to better define its role in ICP determination [2][3][4][5][6][7][8][9][10][11][12] . To date, studies have supported the correlation of ONSD to ICP in neurocritically ill patients [4][5][6][7][8] , both adult and pediatric 9 . Currently, data reflecting normal values for ONSD have been determined from small populations of subjects, both healthy and non-healthy. The majority of normal values are based on nonhealthy patients, with intra-cranial pathology, that have normal invasive ICP measurements 6,7,[10][11][12] . Recent meta-analysis
ORIGINAL ARTICLEdemonstrates normal ONSD ranging from 5.0 to 5.9 mm 2,4,13 , with sensitivity and specificity for intracranial hypertension ranging from 70.8% to 100% and 63% to 100% 13 , respectively.https://www.cambridge.org/core/terms. https://doi