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 a 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, said image processing unit being adapted to identify glints in the image corresponding to reflected light from respective light sources, with the extracted information including a measure of glints being proportional to a number of glints identified in an image; 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.