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pupil

  • Why do some photographs give people strange, red eyes? (AnemoneProjectors, Wikimedia Commons)
    Red-Eyed Pictures
    Walker Rhea
    Some photos appear normal, except for an unearthly red color glowing from the pupils of your loved ones' eyes. Are Grandma and Uncle Felix possessed, or is there some other explanation for this red-eye phenomenon?
  • When you look at something, your retina gets a focused, upside-down image projected by the lens of your eye. (Petr, Novak, Wikimedia Commons)
    Eyes and Alzheimer's
    Walker Rhea
    Researchers think that looking at how quickly a person's pupil dilates when taking cognitive tests could predict if a person is at an increased risk for Alzheimer's disease, even before any obvious symptoms show up.