The production of functional optical parts made of plastics is a growing market and the associated production processes have to be developed to fulfil the increasing quality requirements. In this paper an alternative injection compression molding process using the pvT-behavior of the plastics material is compared to the conventional processing method using an isobaric process path. For both control strategies a cavity pressure loop-control is implemented and used. According to measurements of the mold surface reproduction accuracy and internal properties of the molded part the processing method using the pvT-behavior results in a higher optical part quality in the same cycle time compared to the isobaric processing method.