Article History
Received: 17 July 2018
Accepted: 7 May 2019
First Online: 24 May 2019
Change Date: 22 November 2019
Change Type: Correction
Change Details: An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Competing Interests
: Erdei, G. and Fülep, C. Measuring visual acuity of a client. <i>World Intellectual Property Organization</i><b>WO/2018/020281 A1</b>, PCT/HU2016/000050, patent pending (2018).