Background/Objectives: The search for biomarkers of cognition has garnered significant interest over the past decade, owing to their objective nature, in contrast to the currently available cognition screening tools, which are based on subjective measures. Retina imaging is used in this field because its tissue is considered as an extension of the brain’s vascular and neural structures, reflecting overall brain health. In cognitive disorders, early detection and intervention are essential for achieving the best possible outcomes. To evaluate the physiological correlates of cognitive function in healthy young adults by assessing retinal structures as a non-invasive biomarker of cognitive health. Methods: Eighty healthy young adults participated in this study. Optical Coherence Tomography (OCT) was used to measure retinal morphology, including macular thickness, volume, and retinal nerve fiber layer thickness; then, OCT results were correlated with cognitive assessments using the Montreal Cognitive Assessment (MoCA). Results: Participants with mild cognitive impairment exhibited thinner macular thickness and lower macular volume (p < 0.05, p < 0.001) than participants with normal cognitive function. We also found that macular thickness is positively associated with cognitive function in healthy adults (p < 0.001). The RNFL was found to be normal in all groups, despite changes in macular thickness, indicating that cognitive function in normal individuals depends on macular changes rather than the optic nerve. Conclusions: Macular OCT, which is a cost-effective and widely available tool, can be used to screen for mild cognitive impairment. A clinical trial is recommended to validate these findings and to generate guidelines for assessing cognitive physiology through the retina.