Intra and Interobserver Variability in the B-mode Transorbital Sonographic Measurement of the Optic Nerve Sheath Diameter in Healthy Nepalese Individuals

Abstract

Introduction:Ocular ultrasound has gained importance as a non-invasive imaging technique in the screening, diagnosis and treatment management of intracranial hypertension. The aim of our study was to estimate the intra and interobserver variability on B-mode ocular ultrasound measurement of optic nerve sheath diameter (ONSD).Methods: ONSD of the right eye was measured by ultrasound examination among 120 healthy adult volunteers. The ONSD was assessed 3 mm behind the globe and two serial measurements were taken by two observers who were blinded to each other's findings.Results: Age of the volunteers ranged from 18 to 27 years with a mean age of 23.07 +/-SD of 2.486. The mean of ONSDs of two observers was 4.168 +/-SD of 0.54 mm. The intraclass correlation coefficient for first and second observers was 0.997 and 0.978 respectively at 95% confidence interval. The interobserver intraclass correlation coefficient was 0.977 at 95% confidence interval. No correlation of age and gender was noted with ONSD.Conclusions: B-mode transorbital ultrasound measurement of ONSD is highly reproducible with significant intra-observer and inter-observer agreement. Ultrasound measurement of ONSD measurements can serve as indispensable tool in critical care.

Intra and Interobserver Reliability of Optic Nerve Sheath Diameter in Normal Nepalese Adults using Transorbital Ultrasound

“…The mean difference value was close to zero which signifies no evidence of systemic bias. Previous studies by several authors also support similar findings concerning interobserver reliability [17,19,22,23]. In addition, the scatter plot showed a positive linear correlation with the strong relationship of ONSD measurement between both investigators.…”