Styles 2000.

Study characteristics
Methods	Study design: retrospective case‐control longitudinal Location: UK Time period: initial examination: not reported Outcome: PDR Outcome measurement: mean, median, and percentage difference
Participants	Number of participants: 52 Diabetes type: T1D Inclusion criteria: individuals with T1D for 40 years or more; T1D defined as occurring in those in whom the diagnosis was made before age 30 years and insulin therapy commenced at onset or within 1 year of diagnosis Exclusion criteria: not reported
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/fqam5/?view_only=8a524b3baa3b4a5abb238d66a7782463
Item	Authors' judgement	Support for judgement
Study participation	Unclear	See ‘Notes’ above for link to risk of bias assessment
Study attrition	No	See ‘Notes’ above for link to risk of bias assessment
Prognostic factor measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Outcome measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Adjustment for other prognostic factors	Unclear	See ‘Notes’ above for link to risk of bias assessment
Statistical analysis and reporting	Unclear	See ‘Notes’ above for link to risk of bias assessment