Despite being a well-structured domain, software engineering lacks standardized definitions, metrics, and theories for analyzing eye movements in domain-specific tasks. This gap can be addressed by adapting models from other fields, such as radiology and psychology. In particular, the holistic models of image perception provide a suitable framework for software engineering applications. This paper introduces a unified model of visual perception focused on eye movements during code reviews. It is based on prior research, findings from other studies, and cross-domain theories. Empirical studies on C and C++ code reviews confirm a phase-based process, where experts switch between global scanning and focal viewing. In addition, significant differences in the fixation rate, fixation duration, number of saccades, and AOI-specific metrics highlight the role of expertise in visual processing. The proposed model offers a structured framework for eye-tracking analysis in software engineering, defining relevant metrics and supporting future refinements across various software engineering tasks.