Visual perception is fundamental to human interaction with the external environment. Virtual Reality (VR) systems, transforming digital data into immersive visual experiences, have been widely applied across fields such as gaming, design, medicine, and business through VR head-mounted displays (HMDs). Despite significant advancements in Artificial Intelligence (AI) and display technologies enhancing computational speed, interaction precision, and visual fidelity, prolonged use of VR HMDs often leads to physiological discomforts like eye strain, sleep dis- orders, and hormonal imbalances. These side effects, stemming from disparities between VR screen and natural light, limit comfortable VR usage time to mere minutes. This research addresses the critical issue of reducing physiological discomfort caused by extended VR HMD use, focusing on the impact of synthetic light on the human eye. This research approaches this challenge from two key dimensions: (1) precisely modelling and monitoring the physiological responses of the human eye to light stimulation; and (2) optimising light rendering methods at the software level within VR systems. The main contributions are as follows: Firstly, This research proposes a method for evaluating light stimulation in VR content, quantifying scenes rendered by game engines into stimulation heat maps for various photoreceptors in the hu- man eye. This aids developers in predicting and controlling light stimulation during the design phase. Secondly, This research develops a novel technique for real-time 3D reconstruction of the periocular area using the camera embedded in VR headsets. This method detects subtle physiological changes and provides precise measurements of the eye region, ensuring compliance with health guide- lines. Lastly, This research introduces a colour shift algorithm that models the responses of rods, cones, and melanopsin to different wavelengths. This algorithm adjusts the colour output of VR displays to minimise light stimulation while maintaining accurate colour perception. These methods have been evaluated through specifically designed user experiments, for instance, prolonged virtual museum immersions. The results demonstrate the effectiveness and robustness of the proposed approaches, significantly enhancing the usability and user comfort of VR technology. By alleviating the side effects of VR headsets and extending comfortable VR usage time, this research brings the concept of a "Digital Universe" closer to reality. The enhanced user immersion marks a crucial step toward integrating virtual worlds into daily life, advancing toward a future where digital and physical realities coexist.