Johannitius (809-873 AD), a medieval physician, translator and author.

The medieval physician, translator and author Abū Zayd Ḥunayn ibn Isḥāq al-'Ibādī, best known in the West as Johannitius, is considered the best translator of Greek texts, particularly medical writings, into Arabic. He made great inroads in the art of translation in the Islamic world. In addition to his own translations, Johannitius put significant effort into training pupils and passing knowledge about translation to succeeding generations. He was also a great writer, compiling over 100 books on different subjects, especially medical. Among his own works, the illustrious Kitab al-Ashr Maqalat fil-Ayn (Ten Treatises on the Eye) contains the oldest known illustration of the structure of the eye. It served as the primary source for Galen's theory of vision and subsequent use by Western scholars.