1. A monitoring system for monitoring and/or predicting drowsiness of a driver of a vehicle or a machinery operator, the system being adapted to be arranged in the vehicle or at the machinery, comprising: a set of infrared or near infrared light sources, each light source being arranged in the vehicle or at the machinery such that a substantial amount of the light emitted from the light source incidents on an eye of the driver or operator, the emitted light thereby forming a virtual image of the signal source on the eye including the cornea; an image sensor arranged and oriented such that light reflected from the eye can be captured in an image and adapted to generate consecutive images forming a sequence of images over time, wherein each image contains glints from at least subset of the light sources; an image processing unit adapted to extract information of the glints in the images by processing the images using an image processing algorithm; and a determining unit adapted to determine a drowsiness index based on the extracted information of the glints of the sequence of images, wherein the drowsiness index indicates a degree of drowsiness.