It is not required, but it is recommended that he be knowledgeable about the prayer times, and a sighted person is better than a blind person; because a blind person does not know when the time has entered, and announcing the entry of time by someone who does not know it is difficult. However, if he calls the adhan, it is permissible because the announcement is made through his voice, and it is possible to determine the times by others in general. Ibn Umm Maktum was the muezzin of the Messenger of Allah, peace be upon him, and he was blind. See: Fath Bab al-Inayah, p. 1: 208.