The importance of intravascular pressure as a factor in both the pathogenesis and the progression of diabetic retinopathy has been the subject of considerable controversy ever since Hirschberg categorized the specific diabetic retinal changes in 1890.1
All previous investigators have studied the systemic blood pressure in diabetics and attempted to correlate the severity of the retinal changes with the presence or absence of hypertension. Initially it was stated that severe diabetic retinopathy did not exist without associated systemic hypertension.2,3 However, it was not long until many cases of retinopathy in patients with normal or even lowered blood pressures were documented, and the concept of hypertension as a factor in diabetic retinopathy was ignored.
One of the deficiencies in these studies was that only systemic blood pressure was measured, whereas it is the pressure in the central retinal artery that might more logically influence the diabetic retinopathy.
GAY AJ, ROSENBAUM AL. Retinal Artery Pressure in Asymmetric Diabetic Retinopathy. Arch Ophthalmol. 1966;75(6):758–762. doi:10.1001/archopht.1966.00970050760008