Optimal illumination of the surgical site is crucial for successful surgeries. Current lighting systems, however, suffer from significant drawbacks, particularly shadows cast by surgeons and operating room personnel. We introduce an innovative, module-based lighting system that actively prevents shadows using an array of swiveling, ceiling-mounted light modules. The intensity and orientation of these modules are autonomously controlled by novel algorithms utilizing multiple depth sensors mounted above the operating table. This paper presents our complete system, detailing the algorithms for autonomous control and the initial optimization of the light module setup. Unlike prior work that was largely conceptual and based on simulations, this study introduces a real prototype featuring 56 light modules and three depth sensors. We evaluate this prototype through measurements, semi-structured interviews (n=4), and an extensive quantitative user study (n=11). The evaluation focuses on illumination quality, shadow elimination, and suitability for open surgeries compared to conventional OR lights. Our results demonstrate that the novel lighting system and optimization algorithms outperform conventional OR lights for abdominal surgeries, according to both objective measures and subjective ratings by surgeons.