The crystalline lenses of the eyes undergo mechanical, physiological, morphological and refractive changes to adjust the total refractive power of the eyes to maintain sharp visual acuity whenever an object of regard is moved toward and away from the distance at which humans typically view reading material. The aggregate changes experienced by the crystalline lenses of the eyes to maintain sharp visual acuity is referred to as accommodation. At any given time the crystalline lenses and the eyes may be regarded as being in a state of accommodation.

Most lighting level measurements are characterized in terms of illuminance.While this is useful for indoor applications, illuminance levels are not always as useful for outdoor lighting efficiency characterization.Lighting designers and researchers need a method to accurately characterize their outdoor or low level lighting applications. This invention is directed to a system for approximating the flux density of light on a human retina.Different tasks require different structures of the eye.

Gaze determines a subjects current line of sight or fixation point. The direction of the eye gaze can express the interests of the subject and is a potential porthole into the current cognitive processes. Existing techniques for eye gaze tracking can be divided into video-based techniques and non-video-based techniques. However, non-video-based techniques are intrusive and interfere with the subject, while video-based techniques have significant shortcomings such as lacking sufficient accuracy and imposing physical constraints on the subject.