Perceptual-cognitive skills enable an individual to integrate environmental information with existing knowledge to be able to process stimuli and execute appropriate responses on complex tasks. Various underlying processes could explain how perceptual-cognitive skills impact on expert performance, as articulated in three theoretical accounts: (a) the long-term working memory theory, which argues that experts are able to encode and retrieve visual information from long-term working memory more than less experienced counterparts; (b) the information-reduction hypothesis, which suggests that experts can optimize the amount of information processed by selectively allocating their attentional resources to task relevant stimuli and ignore irrelevant stimuli; and (c) the holistic model of image perception, which proposes that experts are able to extract visual information from distal and para-foveal regions, allowing more efficient global-local processing of the scene. In this systematic review, we examine the validity of the aforementioned theories based on gaze features associated with the proposed processes. The information-reduction hypothesis was supported in most studies, except in medicine where the holistic model of image perception garners stronger support. These results indicate that selectively allocating attention toward important task-related information is the most important skill developed in experts across domains, whereas expertise in medicine is reflected more in an extended visual span. Large discrepancies in the outcomes of the papers reviewed suggest that there is not one theory that fits all domains of expertise. The review provides some essential building blocks, however, to help synthesize theoretical concepts across expertise domains. (PsycINFO Database Record (c) 2019 APA, all rights reserved).