In humans, the pupillary light reflex (PLR) is the change in diameter of the pupil as a response to changes in light intensity. By quantitatively monitoring the pupillary light reflex, there is potential to gain diagnostic knowledge for patients in a variety of situations including those suffering from a traumatic brain injury as well as those undergoing invasive neurosurgery proximal to the optic nerves. To improve the diagnostic capabilities of the PLR, a novel pupillometer was developed. The pupillometer is intended for direct placement on the eye and allows for the continuous stimulation and monitoring of pupillary light reflexes. Tests on anesthetized rabbits demonstrate real-time data acquisition and display, including the pupil diameter and velocities of constriction and dilation. The sensor is in development for implementation as a clinical device to monitor the status of the oculomotor nerves, and may also find applications in the diagnostic assessment of traumatic brain injury or changes in intracranial pressure.