The allure of color-changing cosmetics is understandable. There's something so satisfying—even a little magical—about watching what was once a translucent lip gloss turn to a glossy, bubblegum hue.

As an optometrist, Dr. Ray Corbin-Simon’s job is to make sure her patient’s eyes are healthy. So she was taken aback when one patient recently told her she’d started using eye drops in hopes of ...