»Moon blindness« (lat. morbus lunaticus) has nothing to do with the moonlight and luckily does not afflict humans. It is a disease of the eyes of horses, which recurs periodically. Due to an inflammation of the iris, which is caused by bacteria from food that has been contaminated by mice and rats, the cornea of the eye can cloud over. This leaves a bluish color, which gave the illness its name (even though the moonlight is not blue). If this inflammation continues to happen in an interval of months, it is possible that over the years it can lead to complete blindness of the animal. There is the option of an eye operation in the early stage of the illness, however, this is not straightforward.
Horses have accompanied humans as pets and farm animals for thousands of years. It is assumed that the first domestication of wild horses took place in the 5th millennium BC in Central Asia. Today there are over 200 different horse breeds and 60 million domestic horses in this world alone. So somehow a disease like this tugs at your heartstrings.
What a good thing that this is not the Moon’s fault …