Population	Male and female adults ≥ 18 years of age of any ethnicity with DM and DR (NPDR), diagnosed as per standard clinical protocol
Index prognostic factors	Specific prognostic factors of interest included: routinely collected patient demographics and information, such as age, gender, ethnicity, socioeconomic status, and smoking habits; frequently obtained standard clinical data, such as comorbidities (e.g. presence/absence of cardiovascular disease; cerebrovascular disease; nephropathy, and specifically, chronic kidney failure (defined as estimated glomerular filtration rate (GFR) of < 60 mL/min/1.73 m2); peripheral neuropathy); body mass index (BMI); neck/waist circumference; glycated haemoglobin; blood pressure; low‐density lipoprotein; high‐density lipoprotein; and triglycerides; and functional and structural retinal biomarkers in the prognostic context of the development and progression of PDR. We considered prognostic factors in the absence of treatment for DR.   We expected that prognostic factors would generally have been measured at the time participants entered the studies, and indeed after diagnosis of DR. If measures of prognostic factors were available at other time points, and these coincided in more than one included study, we planned to consider investigating them at these other time points.   We excluded studies evaluating risk factors that ‐ to be measured ‐ require invasive procedures (e.g. aqueous or vitreous samples to measure growth factors in these fluids) not performed in routine clinical practice.
Comparator	Not applicable
Outcomes	Progression from DR (NPDR) to any stage of PDR. We considered participants who received laser PRP for the treatment of PDR to have progressed to the outcome of PDR.
Timing	3 years (± 2 years), 8 years (± 2 years), or lifelong, if available. PDR can occur very rapidly ‐ in days ‐ or take months or years to develop.
Setting	Any clinical setting. No geographical limitations