1Birmingham Midlands Eye Centre, Sandwell and West Birmingham Hospitals NHS Trust, Birmingham, United Kingdom,

2Department of Ophthalmology, Faculty of Medicine, School of Health Sciences, University of Ioannina, Ioannina, Greece,

3Eye Unit, Kantonsspital Winterthur, Winterthur, Switzerland,

4Eye Unit, University of Zurich, Zurich, Switzerland

Correspondence: Walter Andreatta, MD, MSc, FEBO, FRCOphth, Kantonsspital Winterthur, Brauerstrasse 15, 8400 Winterthur, Switzerland; E-mail: [email protected]

Competing interests: The authors report no conflicts of interest.

All authors have made substantial contributions to the following: (1) the conception and design of the study, acquisition of data, or analysis and interpretation of data; (2) drafting the article or revising it critically for important intellectual content; and (3) final approval of the version to be submitted.