In effect, they function 'fake crying.' The quest to manufacture human-like tears continues in laboratories globally.
Sometimes your GP or Optometrist ( eye spet) may also carry out some simple tests. http://xn--80aaandctlru0c8a8fm.xn--p1ai/go.php?go=aHR0cHM6Ly90aGVyYWxpZmUuY29tL2NvdmlkLTE5LWFuZC1kcnktZXllcy8