It's been a while since I watched the movie, but in "A Clockwork Orange" IIRC they were a hallucinogenic (probably acid) to enhance the horror of what he was be

It's been a while since I watched the movie, but in "A Clockwork Orange" IIRC they were a hallucinogenic (probably acid) to enhance the horror of what he was being forced to watch, to further traumatize him against the images of ultraviolence in a negative way. so that when he had the desire to carry out acts of ultraviolence after the 'treatment' he had flashbacks to the horrific visions he was subjected to. And being in eyedrops had the dual purpose of not letting his eyes dry out while he was unable to blink due to his eyelids being clamped open (this was a treatment, not a torture...)