January 15, 2013

Where does Retinopathy start in Diabetes?


dynomiteAlthough you may think the answer is obviously the eyes, you may be wrong. This study has confirmed that retinal changes in Type 1 diabetes occur after neurovascular changes, or blood flow to the brain, are observed. Think of diabetic retinopathy like a stick of dynamite. You don’t get detonation until the flame reaches the explosive material.

A variety of studies has shown that flicker-induced vasodilatation is reduced in patients with diabetes. Flicker-induced vasodilation is a test that stimulates the retinal vessels diameter. Researchers are unclear as to whether reduced neural activity or abnormal neuro-vascular coupling is the reason for T1D retinopathy. This study helped to see where the retinal dysfunction begins.

The study included 50 patients with T1D without retinopathy and 50 healthy control subjects without diabetes. The retinal vascular response to flicker stimulation was measured. In addition, the response in retinal blood velocity to flicker stimulation was studied in a subgroup of patients. Pattern electroretinography (ERG) was used to measure neural retinal function.

The flicker response was significantly reduced in people with T1D. Likewise, the response of retinal blood velocity was reduced in the T1D group. Curiosity, although the flicker response was clearly deficient in the T1D group compared to control group, the pattern ERG tests were not different between the two groups.

The study confirms that flicker responses are reduced early in patients with type 1 diabetes. This is seen before alterations in pattern ERG, a measure of the electrical responses of various cell types in the retina.  This measurement indicates an abnormal neurovascular coupling. Neurovascular coupling is the relationship between brain cell activity and changes in cerebral blood flow (CBF).

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