Observer variation in the sonographic measurement of optic nerve sheath diameter in normal adults.
OBJECTIVE
To quantify the observer variation in the sonographic measurement of optic nerve sheath diameter (ONSD) in normal adults.


METHODS
Sixty-seven normal adult volunteers underwent ultrasound examination of each eye by three independent observers using a 7 MHz sector probe. Three measurements were made of each eye by each observer and a mean value calculated for each eye. Median and 5th-95th centile values for both intra- and inter-observer variation were calculated for the three observers.


RESULTS
The median intra-observer variation was +/-0.1 mm, with 5th-95th centile values of +/-0-0.4 mm. The median inter-observer variation was +/-0.2-0.3 mm, with 5th-95th centile values of +/-0-0.7 mm. Careful review of examination technique by the three observers after the first 17 examinations was shown to reduce both intra- and inter-observer variation.


CONCLUSIONS
The sonographic measurement of ONSD is a readily learned, reproducible technique with low intra- and inter-observer variation. The average inter-observer variation (+/-0.2 mm) is comparable to the inherent variability of the ultrasound machine. The importance of standardisation of examination technique is stressed.
Ballantyne
S A
SA
Department of Radiology and Clinical Physics, Royal Hospital for Sick Children, G46 7PD, Glasgow, UK. s.ballantyne@virgin.net
O'Neill
G
G
Hamilton
R
R
Hollman
A S
AS
D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009186:Myelin Sheath / Q000000981:diagnostic imaging / Q000473:pathology; D015588:Observer Variation; D009900:Optic Nerve / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D014463:Ultrasonography