Allopathic medicine, the common form of medicine most people use today, moves into gear when a person reaches a state of illness. But most illness comes on gradually, from a host of factors often connected to diet and lifestyle. For many of these forms of illness, early testing can reveal nutritional and biochemical markers that researchers have linked to various diseases. One of the most accessible ways to immediately assess aspects of your inner health is through the eye, which is uniquely transparent and available for cheap, effective visual inspection. Thomas Lewis, author of “The End of Alzheimer’s: The Brain and Beyond,” is a microbiologist with a Ph.D. from MIT. He’s done a lot of work on diagnostic testing and how retinal assessment and other laboratory tests can be used to classify your risk factors for chronic disease and COVID-19. The Eye-Brain Connection As just one example, glaucoma and Alzheimer’s …