Narrated Said bin Zaid: Allah's Apostle said, "The Kam'a (i.e. a kind of edible fungus) is like the Manna (in that it is obtained without effort) and its water is a (medicine) cure for eye trouble."
— Sahih Bukhari, Volume 6, Book 60: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)), Hadith #5