The term hemimetamorphopsia comes from the Greek words hèmi (half), metamorphoun (to change the form), and opsis (seeing). It is used to denote a type of "metamorphopsia (i.e. a visual distortion) characterized by a selective distortion of one half of an object or face - although in the latter case the neologism hemiprosopometamor-phopsia may be more appropriate.
References
Nijboer, T.C.W., Ruis, C., van der Worp, H.B., de Haan, E.H.F. (2008). The role of Funktionswandel in metamorphopsia. Journal of Neu-ropsychology, 2, 287-300.
Dictionary of Hallucinations. J.D. Blom. 2010.