Is expiation incumbent upon one who vowed to do something trivial, such as moving his eyes, and if he did not do it, he vowed to slaughter sixty needy persons, and he did not fulfill his vow due to forgetfulness, given that he suffers from obsessive-compulsive disorder, and years have passed since his vow?

The default state is freedom from obligation. Doubt about vows is a form of waswasah (whispering of Satan). It is not obligatory to fulfill a vow if there is doubt about its validity. Similarly, a vow to do something permissible, such as vowing to move one's eyes, is not a valid vow, and expiation is not required for failing to fulfill it.