Article History
Received: 9 January 2018
Revised: 20 February 2018
Accepted: 22 February 2018
First Online: 9 March 2018
Compliance with ethical standards
:
: N. de Vries is consultant to NightBalance, Philips and Olympus and researcher for Inspire and JAZZ pharmaceuticals. P.E. Vonk and A.M.E.H. Beelen declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: For this type of study formal consent is not required.