We report electro-optical studies of twisted SmC* (TSC) cell with high spontaneous polarization which is known to exhibit a V-shape like switching profile. In this study we are particularly interested in the influence of both polarization and ionic charges on the transmitted light intensity. Experimental studies show that the V-shape profile can be strongly affected because of the contribution of the ionic field to the internal one. Indeed, ice show that the V-shape can be either distorted and/or sometimes shifted by the ionic field. The developed theoretical model shows that these effects are related to the azimuthal angle distribution in the cell following the ionic charges redistribution. Our studies explain firstly how the azimuthal angle distribution is modified in the presence and in the lack of ions impurities in the cell and secondly how the transtmitted light intensity is affected. The reported numerical results show a good agreement with experimental one.