The information provided here is not a replacement for a doctor. You shouldn't use it for the purpose of self-diagnosing or self-medicating but rather so you can have a more informed discussion with a professional TCM practitioner.
Because it is a herb specifically indicated to treat night blindness as can be seen on Bat Fece's page.
Bat Feces is a Cool herb that tastes Pungent. It targets the Liver.
Its main actions are: Clears Heat in the Liver and brightens the eyes. Removes Blood Stagnation, clear bruise and reduces accumulations.