In the book Pain: The Gift Nobody Wants, the author, who spent decades treating lepers in India and was the first to definitively prove that leprosy causes the damage it does by destroying the pain-sensing nerves and thus causes victims to inadvertently destroy their own digits and whatnot without even realizing it, describes how they were confused about why so many of the people they were treating were going blind and had chronic eye problems.
They finally figured out that the people who were going blind were ones who had lost the sensation of pain in their eyes (the bacteria that causes leprosy lives in, and eventually destroys, the nerves in the cooler parts of the body like the fingers, toes, nose, eyes, face, etc.) and didn’t blink. It would take months, but eventually the damage would build up until they went blind.
They couldn’t find a very satisfactory solution for this, unless the patients were EXTREMELY responsible about putting in eye drops and forcing themselves to blink at regular intervals. The best treatment they found was suturing the eyelids almost shut so that the tears would coat the exposed portion of eyeball and keep the eye surface clean, but that obviously had ramifications with their ability to see.
Pretty gruesome. Interesting book, even though it’s a few decades old and probably out of date by now as far as its science goes.