פירוש על קידושין 48:16

The rabbis use the phrase “and he destroys it” to exempt a master who accidentally blinds a fetus while trying to help his maidservant deliver her baby. In this case, he did not intend to do anything to an eye at all. However, if he intended to perform an operation on the eye and he accidentally put it out, the slave does go free, because he intended to do something to the eye.