This review investigates how individual reader characteristics and textual characteristics jointly influence cognitive processing during scientific text reading, based on eye-tracking research between 2012 and 2025. A total of 37 studies focusing on scientific texts were analyzed to identify trends in research questions, methodologies, and metrics. The review highlights that reader characteristics--such as prior knowledge, reading ability, spatial skills, and attention-shifting capacity--substantially affect eye movement behaviors. At the same time, features of the scientific text-structural organization, representational format, and complexity--influence how readers allocate attention and how researchers select and interpret eye-tracking metrics. Readers with higher scientific reasoning or spatial ability tend to exhibit more strategic rereading patterns and greater attentional control, particularly when processing complex or contradictory information. The review also discusses the implications for adaptive learning, emphasizing the potential of eye-tracking to inform differentiated instruction, enhance reading interventions, and support personalized feedback in science education.