Musannaf Ibn Abi Shayba 18:1147

Abu Bakr narrated to us, he said: Zayd ibn al-Hubab narrated to us, from Sufyan, from Khalid al-Nayli, from al-Hakam and Hammad, that they both said regarding a man who wounded another man on the head, and his eye was lost, but not from that wound: Al-Hakam said: "If they testify that it was lost because of the blow, then it is permissible [to hold him liable]." Hammad said: "If they testify that he struck him on the day he struck him, and it [the eye] was healthy, then it is permissible."