By Oliver Astley An early sign of dementia might be noticed in vision changes before memory loss, suggests a neurologist. This potential early warning usually happens before the well-known memory loss linked to Alzheimer’s disease. Health researchers from the University of California in San Francisco believe that the initial signs of dementia could be detected by eye doctors if they know how to spot a condition known as posterior cortical atrophy (PCA), also referred to as Benson’s syndrome. This condition impacts brain areas responsible for tasks like spelling, calculations, spatial perceptio…