| Study | Reason for exclusion |
|---|---|
| Abougalambou 2015 | Cross‐sectional study |
| Adderley 2020 | No data on development of PDR |
| Adnitt 1970 | No data on development of PDR |
| Advance Collaborative Group 2008 | No data on development of PDR |
| Alattas 2022 | Ineligible study design |
| Altaf 2013 | Cross‐sectional study |
| Ashakiran 2011 | Unable to access publication ‐ no contact details for author |
| Askarishahi 2011 | Cross‐sectional study |
| Barr 2001 | RCT |
| Beulens 2009 | RCT |
| Borch‐Johnsen 1987 | No data on development of PDR |
| Bresnick 1987 | Ineligible patient population |
| Brinchmann‐Hansen 1985 | RCT |
| Burton 2000 | Case report |
| Cantagallo 1989 | Review article |
| Chahal 1985 | No data on development of PDR |
| Chaturvedi 1998 | RCT |
| Chawla 2015 | Cross‐sectional study |
| Chen 2017 | No data on development of PDR |
| Chen 2020 | Abstract ‐ no corresponding publication found |
| Chew 2014 | RCT |
| Chittimoju 2013 | Cross‐sectional study |
| Chung 2019 | No data on development of PDR |
| Cikamatana 2007 | No data on development of PDR |
| Cohen 1991 | Rsk factors not given in a way that can be used to determine risk of PDR |
| Colin 2012 | Abstract ‐ no corresponding publication found |
| Cuadras 2017 | Cross‐sectional study, no data on development of PDR, and an abstract only |
| Danielsen 1983 | Cross‐sectional study |
| DCCT 1993 | RCT |
| Ding 2020 | Ineligible study design ‐ DR self‐reported |
| Dizdarevic 2012 | Cross‐sectional study |
| Duckworth 2009 | RCT |
| Dujic 1998 | Cross‐sectional study |
| Elshafei 2011 | Cross‐sectional study |
| Estacio 2000 | RCT |
| ETDRS 1991c | Ineligible study design (RCT) |
| Foshati 2019 | Cross‐sectional study |
| Friberg 1985 | No data on development of PDR |
| Fung 2011 | Cross‐sectional study |
| Fusi‐Rubiano 2015 | Cross‐sectional study |
| Gallagher 2018 | No data on development of PDR |
| Gao 2014 | Cross‐sectional study |
| Garcia‐Medina 2011 | No data on development of PDR |
| Garmo 2018 | No data on development of PDR |
| Geetha 2019 | Ineligible study design |
| González‐Villalpando 1994 | Cross‐sectional study |
| Grauslund 2011 | Review article |
| Gupta 2019 | Survey, no data on development of PDR, and abstract only |
| Haffner 1993 | No data on development of PDR |
| Hamman 1989 | Cross‐sectional study |
| Hautala 2018 | No data on development of PDR |
| Henricsson 1997 | No data on development of PDR |
| Hoang 2020 | Cross‐sectional study |
| Holman 2008 | No data on development of PDR |
| Holt 2019 | No data on development of PDR |
| Hwang 2019 | No data on development of PDR |
| Jacobsen 2003 | Unable to access publication ‐ author contacted but no response |
| Janka 1989 | No data on development of PDR |
| Jin 2018 | Cross‐sectional study |
| Jonas 2017 | No data on development of PDR |
| Kawasaki 2005 | Review article |
| Keech 2007 | RCT |
| Kingsley 1988 | No data on development of PDR |
| Klein 1988 | No data on development of PDR |
| Kohner 1986 | RCT |
| Kornerup 1955 | No data on development of PDR |
| Kroc Collaborative Study 1984 | RCT |
| Krolewski 1986 | Unspecified number of patient population less than 18 years of age |
| Kulenovic 2006 | No data on risk factors |
| Kyari 2014 | Cross‐sectional study |
| Lamoureux 2018 | No data on development of PDR |
| LaPorte 1986 | No data on development of PDR |
| Lauritzen 1983 | RCT |
| Lee 2010 | No data on development of PDR |
| Lee 2011 | Cross‐sectional study |
| Leese 2004 | Correspondence author contacted to provide clarification on definition of outcome. Outcome may have included participants with pre‐PDR, so not included in review |
| Leske 2003 | No data on risk factors |
| Li 2019 | Ineligible outcomes |
| Lim 2015 | Abstract |
| Lima 2016 | Ineligible study design |
| Lin 2010 | Ineligible outcomes |
| Liu 2019 | Cross‐sectional study, and abstract only |
| Lorenzi 1983 | Ineligible patient population ‐ adolescents |
| Low 2021 | No data on development of PDR |
| Lu 2012 | Cross‐sectional study |
| Lu 2013 | Cross‐sectional study |
| Lv 2020 | Cross‐sectional study |
| Malik 2005 | Cross‐sectional study |
| Malik 2018 | Cross‐sectional study |
| Man 2018 | No data on development of PDR |
| Marshall 1993 | No data on development of PDR |
| Mathur 2016 | Correspondence author contacted to provide clarification on definition of outcome. Supplementary material provided which confirmed outcome of 'severe retinopathy' included participants with diabetic macular oedema |
| Mehlsen 2011 | No data on development of PDR |
| Mehta 2019 | RCT |
| Minuto 2009 | Cross‐sectional study |
| Mitchell 1985 | No data on development of PDR |
| Mohd Ali 2016 | Cross‐sectional study |
| Moon 2018 | Abstract |
| Mowatt 2013 | Cross‐sectional study |
| Muhlhauser 1986 | Cross‐sectional study |
| Muqit 2014 | No data on risk factors |
| Nguyen 2009 | Cross‐sectional study |
| Nicolucci 1993 | Cross‐sectional study |
| Nordwall 2004 | No data on development of PDR |
| Ohtani 1985 | Ineligible study design |
| Padmajeya 2019 | Abstract |
| Paetkau 1977 | Cross‐sectional study |
| Pardhan 2004 | Cross‐sectional study |
| Park 2015 | Cross‐sectional study |
| Parving 1988 | Cross‐sectional study |
| Pettitt 1980 | No data on development of PDR |
| Pugliese 2012 | Cross‐sectional study |
| Rahul 2015 | Cross‐sectional study |
| Rasoulinejad 2022 | Cross‐sectional study |
| Raum 2015 | Cross‐sectional study |
| Ravi Theja 2017 | Cross‐sectional study, and abstract |
| Reichard 1991 | RCT |
| Resman 1993 | Ineligible study design |
| Romero 2007 | No DR at baseline |
| Romero‐Aroca 2016 | No data on development of PDR |
| Rudnisky 2012 | No data on development of PDR |
| Schellhase 2003 | No data on development of PDR |
| Shriwas 1996 | Cross‐sectional study |
| Singh 2020 | No data on development of PDR |
| Sjolie 1985 | No data on risk factors |
| Srikanth 2015 | Ineligible participant population |
| Takaike 2018 | Definition of outcome unclear and unable to contact authors to clarify |
| Tapp 2006 | No data on risk factors |
| Taylor 1997 | Cross‐sectional study |
| Thapa 2015 | Cross‐sectional study |
| Tripathi 2010 | No data on risk factors |
| Tseng 2012 | No data on development of PDR |
| Tu 2011 | No data on development of PDR |
| UKPDS Group 1996 | No data on risk factors |
| Van Leiden 2003 | No data on development of PDR |
| Villena 2011 | Cross‐sectional study |
| Wang 2006 | No data on risk factors |
| Xie 2009 | Cross‐sectional study |
| Yokoyama 1997 | Cross‐sectional study |
| Zhou 2006 | No data on development of PDR, and abstract only |
DR: diabetic retinopathy; PDR: proliferative diabetic retinopathy; RCT: randomised controlled trial