In folklore, moonlight sometimes has a harmful influence. For example, sleeping in the light of a full Moon on certain nights was said to transform a person into awerewolf. The light of the Moon was thought to worsen the symptoms of lunatics, and to sleep in moonlight could make one blind, or mad. Nyctalopia (night blindness caused by a lack of vitamin A) was thought to be caused by sleeping in moonlight in the tropics.In popular literature, The fictional short story "The Trade Wind", by Morgan Robertson, a popular author of sea stories, describes the adventures of an entire crew of sailors afflicted by "Moon Blindness" (a disease of horses now known as equine recurrent uveitis). It presumes that the reader is familiar with this condition and accepts the premise that it is a known painful but temporary result of sleeping in bright moonlight. In this case it occurred as the aftermath of passing-out drunk on deck following a party, and explores how such a group might deal with the handling of a sailing vessel on the open sea without eyesight.The story first appeared in Collier's Weekly in the late 1800s and was later included in the 1899 collection "Where Angles Fear To Tread, and other Tales of the Sea" (available on-line).