Table 2.

Strengths and limitations of ONSD ultrasound.

Strengths	Limitations
•Safe and non-invasive [55,56] •Point of care bedside test [57] •Quick to perform [58] •Correlation with invasive ICP measurements [41] •Low inter operator variability [59] •Not affected by age in adults, body mass index, head circumference, or blood pressure [60]	•Potentially false positives for raised ICP in Graves orbitopathy, ONS meningiomas, leukaemic infiltration, orbital congestion [59] •Artefact from surrounding collagen tissue can distort optic nerve [61] •Variation in normal range by ethnicity [57,[62], [63], [64]] •Variation in age with children [65] •Minimal guidance for acting on abnormal measurements •May be operator dependent

ICP: Intracranial pressure. ONS: Optic nerve sheath.