It is a very common belief in many of the Islamic countries that some people have evil eyes and that some people can cast a spell. There are many stories that we grow up with about these evil eyes and magic spells, most of them are just that stories, but growing up with such stories make this issue on our minds many times.
As for the evil eye, people mean a person can have such an evil power to envy them or someone to the point that some harm can afflict them.
[113:0] In the name of God, Most Gracious, Most Merciful
[113:1] Say, "I seek refuge in the Lord of daybreak.
[113:2] "From the evils among His creations.
[113:3] "From the evils of darkness as it falls.
[113:4] "From the evils of the troublemakers.
[113:5] "From the evils of the envious when they envy."
This verse teaches us that there are envious people who have evil. Although this verse confirms that some people have evil (eyes) when they are envious (you can be blind but have that envious feeling), Muslims totally forget that NO ONE HAS ANY POWER of his/her own. It is GOD who permits any thing to happen to people and God does not permit this to happen except for those who forget about HIM.
People who strongly believe in this "Evil eye" usually are the same ones who forget that NO ONE can harm them even if she or he is envious, as long as they remember and believe that , God is the ONE who is in control, not that person. It is a test for the true believers, the true believers always remember that God is in control and NO ONE will harm them without God's permission.
[64:11] Nothing happens to you except in accordance with GOD's will. Anyone who believes in GOD, He will guide his heart. GOD is fully aware of all things.
I personally believe that God set these envious people with evil eye to cause harm to those who forget about God and believe that a human being like them can harm them or their loved ones. We as believers should know that God is in full contorl and that no one but God can benefit us or harm us. We should follow the Quran and seek protection from such envious people as sura 113 teaches this one way to remember God.
As for casting a spell, Quran does mention that magic exist and that humans were taught magic at a certain stage but they abused it and now Quran condemn those who practice magic.
Witchcraft Condemned [2:102] "They pursued what the devils taught concerning Solomon's kingdom. Solomon, however, was not a disbeliever, but the devils were disbelievers. They taught the people sorcery, and that which was sent down through the two angels of Babel, Haroot and Maroot. These two did not divulge such knowledge without pointing out: "This is a test. You shall not abuse such knowledge." But the people used it in such evil schemes as the breaking up of marriages. They can never harm anyone against the will of GOD. They thus learn what hurts them, not what benefits them, and they know full well that whoever practices witchcraft will have no share in the Hereafter. Miserable indeed is what they sell their souls for, if they only knew."
As you can see the TRUE believers will be protected by God, but those who try to use these people who claim to cast a spell or being magicians are going for other than God and therefore leaving God's protection.