Optic nerve ultrasonography (optic nerve sheath diameter sonography) has been proposed as a noninvasive, quick method for diagnosing increased intracranial pressure
..Accuracy estimates were similar among studies stratified by patient age, operator specialty and training level, reference standard, sonographer blinding status, and cutoff value. The optimal cutoff for optic nerve sheath dilatation on ultrasonography was 5.0 mm.
Optic nerve ultrasonography can help diagnose increased intracranial pressure. A normal sheath diameter measurement has high sensitivity and a low negative likelihood ratio that may rule out increased intracranial pressure, whereas an elevated measurement, characterized by a high specificity and positive likelihood ratio, may indicate increased intracranial pressure and the need for additional confirmatory tests.