If the occipito-temporal cortex is involved, the visual hallucinations become complex and colourful, and scenes of varying complexity may be 'seen'. Perceptive illusions may occur, which are classified as simple or complex. Simple illusions are where objects appear distorted and seem to have changed in size (macropsia or micropsia), shape (metamorphopsia), illumination, colour or clarity. Lines may appear wavy (dysmorphopsia), objects may appear inclined (plagiopsic) and there may be a loss of colour (achromatopsia). Complex illusions are where objects appear disorientated in distance (macroproxiopia, microtelepsia), appear to be distant and minute (teleopsia), appear to have a loss or enhancement of stereoscopic vision, or are persistent or recurrent (palinopsia) (for reviews see Dreifuss, 1985 ; Sveinbjornsdottir and Duncan, 1993 ).