. Author manuscript; available in PMC: 2021 Apr 16.
Published in final edited form as: Br J Ophthalmol. 2020 Jun 12;105(4):549–554. doi: 10.1136/bjophthalmol-2020-315836
Open access This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/.