The term kalopsia comes from the Greek words kakos (bad, unpleasant) and opsis (seeing). It is used to denote a negative affective connotation of sensory, illusory, and hallucinatory phenomena, in the sense that these are perceived as ugly, sinister, and/or menacing. The term kakopsia is used in opposition to *kalopsia (i.e. seeing things as beautiful, friendly, and/or comforting).
References
Critchley, M. (1949). Metamorphopsia of central origin. Transactions of the Ophthalmologic Society of the UK, 69, 111-121.
Dictionary of Hallucinations. J.D. Blom. 2010.