Degree of diabetic retinopathy depends on –
Risk factors for diabetic retinopathy 

Duration of disease after onset of puberty :- Most important risk factor.
Other :- Age of onset (before puberty), sex, poor glycemic control, hypertension, smoking, poor renal status, obesity, hyperlipidemia, pregnancy.
Type of disease
Duration of disease
Severity of disease
Retinal involvement
Duration of disease