Treatments to halt or reverse Alzheimer's disease remain elusive, but researchers reported progress Sunday in early diagnosis, including the use of a chemical marker, visible via brain scan, to detect substances associated with the disease. Other researchers are working on less invasive techniques, such as measuring physical or sensory changes to smell and vision that occur during early stages of the disease. In one study, scientists are gauging the width of blood vessels in the retina. The data were presented Sunday at the Alzheimer's Association International Conference on Alzheimer's Disease. Among the possible advances in early detection are chemical tracers, some of which tag clumps of a sticky substance in the brain called amyloid, and others that mark amyloid and a protein called tau—both thought to contribute to the disease. These tracers make Alzheimer's pathology visible in a living brain, which until now could only be seen upon autopsy. The new findings show the presence of amyloid on a PET scan might lead to greater memory loss or other cognitive troubles.