How did people think about examining the retina as a place of early detection for Alzheimer’s?

Some of the systems that go awry early in the brain in Alzheimer’s such as changes in the cholinergic system (a neurotransmitter chemical system that signals between neurons and we know that it’s affected very early in the disease. We know where that same system is in the retina and we know what layer of cells that chemistry is most active in, so we’ve found early changes in that layer in preclinical Alzheimer’s disease in a past study which led to this new trial.