Table 1. Basic information of each group.

Groups	n	Gender (M/F)	Age (range), y
Control group	30	16/14	56.38±9.48 (45-67)
NDR group	33	16/17	56.5±7.45 (45-67)
NPDR group	32	15/17	58.6±9.41 (42-72)
PDR group	34	17/17	57.86±8.2 (45-75)
χ2/F		0.008	0.171
P		0.93	0.915

NDR: No diabetic retinopathy; NPDR: Non-proliferative diabetic retinopathy; PDR: Proliferative diabetic retinopathy.