The youth, identified only as "Luis A.," claims he has almost no vision in his right eye since the injury, The Santiago Times reported Tuesday.
"The state should take responsibility for this type of repressive measure, which is not proportional to the situation the police find themselves in," said Tomas Ramirez, the youth's attorney.
Luis and other protesters were injured March 28 when security forces fired paintballs into a crowd. Video shot on cell phones show police shooting indiscriminately at head height.
While the youth's surgery was covered by Chile's national health system, he must pay for the cost of medication.
A representative of a human rights group said this was not the first case of injury from paintballs fired by police.
Javiera Pizarro, of the Human Rights Observatory in Santiago, said the weapon was fired at the upper bodies of protesters "to deter people from going to future demonstrations."
The president of the Student Federation of Universidad Catolica, Diego Vela, charged use of the guns was "completely opposed to their supposed object of public order. They are putting at risk the safety of all attendees."