Obviously its okay to want things, but when those desires demand more from our affections than they warrant, it has turned into lust of the eyes.
Biblical example: Samson, in Judges 14
1 Samson went down to Timnah and saw there a young Philistine woman. 2 When he returned, he said to his father and mother, "I have seen a Philistine woman in Timnah; now get her for me as my wife." 3 His father and mother replied, "Isn't there an acceptable woman among your relatives or among all our people? Must you go to the uncircumcised Philistines to get a wife?" But Samson said to his father, "Get her for me. She's the right one for me."
Samson was morally prohibited from marrying an unbelieving foreigner, yet he was ruled by the lust of the eyes.