Neurosurgeons and scientists evaluated use of state-of-the-art optical technology built into commercial grade operating microscopes used in neurosurgery to detect the glow produced by adding the pro-drug 5-ALA to experimental malignant brain tumors. 5-ALA is approved for administration to patients to increase the detection of the margin of invading brain glioma tumors, and thereby allow for a wider or more extensive brain tumor removal. As the most important visualization tool in daily use for neurosurgery, operating microscopes are gaining advanced functionality with innovative illumination modes.