Search results
Results from the WOW.Com Content Network
The human eye contains three types of photoreceptors, rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs). Rods and cones are responsible for vision and connected to the visual cortex. ipRGCs are more connected to body clock functions and other parts of the brain but not the visual cortex.
The pupil of the human eye can range in size from 2 mm to over 8 mm to adapt to the environment. The human eye can detect a luminance from 10 −6 cd/m 2, or one millionth (0.000001) of a candela per square meter to 10 8 cd/m 2 or one hundred million (100,000,000) candelas per square meter.
The human eye, showing the iris and pupil. In 1802, philosopher William Paley called it a miracle of "design."In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". [3]
The visual system includes the eyes, the connecting pathways through to the visual cortex and other parts of the brain (human system shown). The eye is the sensory organ of the visual system. The iris , pupil , and sclera are visible
Distribution of rods and cones along a line passing through the fovea and the blind spot of a human eye [7] Most vertebrate photoreceptors are located in the retina. The distribution of rods and cones (and classes thereof) in the retina is called the retinal mosaic. Each human retina has approximately 6 million cones and 120 million rods. [8]
A recent study on the evolutionary purpose for the inverted retina structure from the APS (American Physical Society) [13] says that "The directional of glial cells helps increase the clarity of human vision. But we also noticed something rather curious: the colours that best passed through the glial cells were green to red, which the eye needs ...
Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. This is known as the pupillary light reflex . The iris contains two groups of smooth muscles; a circular group called the sphincter pupillae , and a radial group called the dilator pupillae .
The macula (/ˈmakjʊlə/) [1] or macula lutea is an oval-shaped pigmented area in the center of the retina of the human eye and in other animals. The macula in humans has a diameter of around 5.5 mm (0.22 in) and is subdivided into the umbo, foveola, foveal avascular zone, fovea, parafovea, and perifovea areas.