The repetition in visual hallucinations of certain simple elements—dots, wavy lines, parallel figures, and other formations—led to the hypothesis that these images might arise in the retinal ganglionic network or from the anatomic structure of the eye. While usually unseen, on occasion they may be seen, particularly in schizophrenic patients who are frequently unable or unwilling to screen out meaningless stimuli in order to focus on meaningful ones. The type of secondary elaborations would vary with the state of the individual.