Understanding the user experience requires gathering self-reported and physiological information. In Virtual Reality (VR), heart rate, skin responses, gaze, brain, and muscle activity can provide a better understanding of how users process perceptual cues and respond to them. While the use of physiological measures is typically done for the assessment and improvement of the user experience, recent trends have shown their application for customizing VR experiences to the unique responses of the users. The purpose of this literature review is to analyze the use of physiological measures in VR customization to identify the state of the art, gaps, and opportunities. A total of 25 articles from indexed journals found in Scopus, PubMed, Web of Science, and IEEE, in addition to top tier conferences such as IEEE VR and CHI within the last five years were reviewed. The review indicates that while assessment continues to be a main field of application of physiological measures, the recent availability of consumer-level VR and the growth of ubiquitous physiological sensors are enabling their use as user input devices for customized and adaptive user experiences.