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
Retina is key to lessening the sum of messages sent to the higher regions of the brain. In some lower vertebrates (e.g. the pigeon), there is a "centrifugal" control of messages – that is, one layer can control another, or higher regions of the brain can drive the retinal nerve cells, but in primates this does not occur. Using optical coherence tomography (OCT) there are 18 layers that can be identified in the retina. The layers and anatomical correlation are as follows: From innermost to outermost, the layers identifiable by OCT are as follows: Retinal development begins with the establishment of