Tight blood pressure control in type 2 diabetes patients reduced progression of DR by 34% and risk of deterioration by 47% after 9 years.
UK Prospective Diabetes Study Group. Tight Blood Pressure Control and Risk of Macrovascular and Microvascular Complications in Type 2 Diabetes: UKPDS 38. BMJ. 1998; 317: 703. http://www.bmj.com/content/317/7160/703