Sayyiduna Ali (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) commanded us to carefully examine the ears and eyes (of the sacrificial animal).
Because it is preferable to slaughter an animal with sound eyes and ears, this does not mean that it is forbidden to sacrifice an animal with (minor) defects in the eyes or ears.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر أفعال اختلف الناس فى إباحته للمحرم، نصت سنة النبى صلى الله عليه وسلم أو دلت على إباحتها / 2914