Vision in fishes layers of other neurons before it reaches them. The retina contains rod cells and cone cells. Within the retina, rod cells provide high visual sensitivity (at the cost of acuity), being used in low light conditions. Cone cells provide higher spatial and temporal resolution than rods can, and allow for the possibility of colour vision by comparing absorbances across different types of cones which are more sensitive to different wavelengths. The ratio of rods to cones depends on the ecology of the fish species concerned, "e.g.", those mainly active during the day in clear waters will have more cones than
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