Human eye Human eye The human eye is an organ which reacts to light and pressure. As a sense organ, the mammalian eye allows vision. Human eyes help to provide a three dimensional, moving image, normally coloured in daylight. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can differentiate between about 10 million colors and is possibly capable of detecting a single photon. Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment
Helmethead gecko are flattened and spatulate. Helmethead geckos can be anywhere from light grey to dark brown, either uniform in color or with pale or dark blotches. The underside of the gecko is light-colored. This gecko is mainly nocturnal, and whereas most lizards are diurnal and have lost the rod structures in the retina that is typical of vertebrates, retaining only cones, this gecko has further adapted its eyes so that it has some degree of color vision at night. The gecko has developed a multifocal optical system which enables it to distinguish between light at different wavelengths. The pupils of this