24. Retinal vessel caliber ‐ Studies undertaking multivariable regression analyses to determine the effect of retinal vessel caliber at baseline on progression to PDR.

Study	Study type	Time years	N at baseline	Adjustment factors	Effect estimate			P value	Comments
					Type	Value	95% CI
Type 1 diabetes
Roy 2006	Prospective cohort	6	725	HbA1c, age, sex, BMI, socioeconomic status, proteinuria, central retinal artery equivalent, ocular perfusion pressure, refractive error.	OR	3.49	1.44 to 8.46	0.03	Central retinal vein equivalent ≥ 272.27 vs ≤ 235.97
WESDR Report XIX	Prospective cohort	10, 14	996	HbA1c, DM duration, DR severity at baseline, sex, mean arterial pressure, anti‐BP medication	RR	4.28	1.50 to 12.19	0.006	Larger venular diameters
Type 2 diabetes
WESDR Report XXI	Prospective cohort	10	962	HbA1c, DR severity at baseline, age	HR	1.17a 0.91b	0.68 to 2.04 0.46 to 1.80	0.57     0.78

BMI: body mass index; CI: confidence interval; DBP: diastolic blood pressure; DM: diabetes mellitus; DR: diabetic retinopathy; HbA1c: glycated haemoglobin/haemoglobin A1c; HR: hazard ratio; NPDR: non‐proliferative diabetic retinopathy; OR: odds ratio; PDR: proliferative diabetic retinopathy; RR: risk ratio; SBP: systolic blood pressure; vs: versus

^aLarger central retinal vein equivalent
^bLarger central retinal artery equivalent