Fovea: Perbedaan antara revisi
Konten dihapus Konten ditambahkan
k Bot: Perubahan kosmetika |
k Bot: Perubahan kosmetika |
||
Baris 63:
The fovea is also a pit in the surface of the retinas of many types of fish, reptiles, and birds. Among mammals, it is found only in [[simian]] [[primates]]. The retinal fovea takes slightly different forms in different types of animals. For example, in primates, cone photoreceptors line the base of the foveal pit, the cells that elsewhere in the retina form more superficial layers having been displaced away from the foveal region during late [[fetus|fetal]] and early [[postnatal]] life. Other foveae may show only a reduced thickness in the inner cell layers, rather than an almost complete absence.
The only photo-receptors located in the fovea of most humans are three kinds of cone photo receptors. The red, blue, and green allow the eye to see the colours that humans need for survival; however, some organisms are known to possess four independent channels for conveying color information, or possessing four different types of cone cells in the eye, a characteristic called ''tetrachromacy''. Organisms with tetrachromacy are called [[tetrachromats]]. The rods are located on the fovea's periphery. This assists the eye in seeing in the dark. Humans have an area in the centre of their fovea which lacks blue cones, possibly due to the effect of [[chromatic aberration]] on blue light.<ref>{{cite journal|last=Wald|first=George|title=Blue-Blindness in the Normal Fovea|journal=[[Journal of the Optical Society of America]]|year=1967|volume=57|pages=
-->
|