After 9 years of tight blood pressure control, patients with type 2 diabetes had a 34% reduction in retinopathy progression and a 47% reduction in risk of visual acuity deterioration by three lines, when they had a 10/5 mmHg reduction in blood pressure.
Turner, Robert, Rury Holman, Irene Stratton, Carole Cull, Valeria Frighi, Susan Manley, David Matthews, Andrew Neil, Heather McElroy, Eva Kohner, Charles Fox, David Hadden, and David Wright. Tight Blood Pressure Control and Risk of Macrovascular and Microvascular Complications in Type 2 Diabetes. BMJ. 1998; 317(7160): 703-13. http://www.bmj.com/cgi/content/abstract/317/7160/703