Patching an eye shut is useful for several conditions. The most common one is amblyopia, where an eye becomes “lazy” from disuse in childhood. A patch is used to cover the good eye and force the “lazy” eye to work better. Patching is also used for therapeutic effect in cases of eye pain. If you are having extraordinary eye pain from a corneal abrasion the eye can be patched shut. However, I typically avoid prolonged patching in an eye that has an active infection, as bacteria like warm, dark places. Patching can also be useful when an eye won’t shut. For example, after retrobulbar block anesthesia (used for difficult or prolonged eye surgery), the eye will not close all the way for several hours. To keep the eye from drying out, the eye is patched shut overnight.