Correlation of measurement of optic nerve sheath diameter with ultrasound and magnetic resonance imaging.

Sir,

The article by Shirodkar et al.[1] on the correlation of measurement of optic nerve sheath diameter (ONSD) measured using ultrasound and magnetic resonance imaging (MRI) was very interesting. ONSD measurement has been correlated well with raised intracranial pressure.[2] Bedside measurement of ONSD by ultrasound offers a very important advantage over other modalities and helps in early initiation of treatment.

This has been a very well done study, but we believe the study could have been improved if the following points were considered:

The study does not tell us who has done the ultrasonographic examination. It is very important if the study shows that examination done by an intensivist is having good correlation with MRI. The experience of the person doing the ultrasonography is also important as most previous studies have been done by experienced radiologists

The inter and inter observer variations are not noted both in the ultrasonographic and MRI examination.[3] These are important sources of error in studies where an individual's observations are taken in the calculation. Most of the studies on ONSD have used two people for performing the ultrasonography and the mean value of both the observers are taken into account.[4] It would have been better if two persons were given the task of doing ultrasonography and reporting of the MRI for the same reading

Potgieter et al.[5] have shown that 4-h workshop was sufficient to teach novice ultrasonographers to learn measurement of ONSD. The study could have added some data on the training needed to do an examination.

This has been a very well done study, but the above would have helped in increasing our knowledge in the field of measurement of ONSD. It would have added to bedside management by an intensivist, the training and would have helped to establish the role of ultrasound in diagnosis, monitoring and management of raised intracerebral pressure.

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Conflicts of interest

There are no conflicts of interest.