Purpose: The ultrasound-based evaluation of the optic nerve sheath diameter (ONSD) has been
demonstrated to be useful for detecting raised intracranial pressure. In order to
be feasible in clinical workup, the test qualities of transorbital ultrasonography
need to be determined. The aim of this study was therefore to establish normal values
and to assess the intra- and interobserver reliability of this method.
Methods: Using a 9–3MHz linear array transducer, the ONSD of 40 healthy subjects was independently
measured bilaterally by two investigators.
Results: Depicting the optic nerve and its sheath was possible in all inividuals. The mean
ONSD was 5.4±0.6mm with a range of 4.3–7.6mm. The intraobserver reliability was found
to be high with values between 0.92 and 0.97. Pearson's correlation coefficient between
the two investigators was 0.81 on the right side and 0.84 on the left. There was no
correlation between ONSD and age, body mass index or gender.
Conclusion: In summary, transorbital B-mode sonography is a feasible method to assess the ONSD
with a high intra- and interobsever reliability. Normal values on ONSD are presented
in this study that will be useful in future studies on pathological conditions.
