Schematic diagram of the human eye, with the fovea at the bottom. It shows a horizontal section through the right eye

The fovea, also known as the fovea centralis, is a part of the eye, located in the center of the macula region of the retina. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow" is an oval Yellow spot near the center The vertebrate retina is a light sensitive part inside the inner layer of the Eye. ^{[1] [2]} The fovea is responsible for sharp central vision (also called foveal vision), which is necessary in humans for reading, watching television or movies, driving, and any activity where visual detail is of primary importance. In Psychology, visual perception is the ability to interpret information from Visible light reaching the Eyes The resulting Perception is also The foveal system of the human eye is the only part of the Retina that permits 100% visual acuity Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic The fovea is surrounded by the parafovea belt, and the perifovea outer region:^[2] the parafovea is the intermediate belt where the ganglion cell layer is composed of more than five rows of cells; the perifovea is the outermost region where the ganglion cell layer contains two to four rows of cells, and is where visual acuity is below the optimum. In Anatomy, a ganglion (pl ganglia) is a tissue mass. Neurology In neurological contexts ganglia are composed mainly of This, in turn, is surrounded by a larger peripheral area that delivers highly compressed information of low resolution. Peripheral vision is a part of vision that occurs outside the very center of gaze The optic nerve carries approximately 50% of nerve fibers for transmitting information from the fovea, while the other 50% carry information from the rest of the retina. The optic nerve, also called cranial nerve II, is the Nerve that transmits visual information from the Retina to the Brain.

Description

The term fovea comes from the Latin, meaning pitty or pitfall. As an anatomical term, there are several foveae around the body, including in the head of the femur. The femur is the thigh bone In Humans, it is the longest, most voluminous and strongest Bone.

In the human eye the term fovea (or fovea centralis) denotes the pit in the retina which allows for 100% acuity of vision. The vertebrate retina is a light sensitive part inside the inner layer of the Eye.

The diagram shows the relative acuity of the right human eye (horizontal section) in degrees from the fovea. ^[3]

In the human fovea the ratio of ganglion cells to photoreceptors is close to one; almost every photoreceptor has one ganglion cell receiving data from it. A ganglion cell (more correctly a retinal ganglion cell or RGC) is a type of Neuron typically located near the inner surface of the Retina Photoreceptor can refer to In anatomy/cell biology Photoreceptor cell: a photosensitive cell most commonly referring to a specialized type of neuron That is why it has little loss of sensory data, thus it is the area of the eye where most details can be seen. ^[4]

The human fovea has a diameter of about 1. 0 mm with a high concentration of cone photoreceptors. Cone cells, or cones, are Photoreceptor cells in the Retina of the Eye which function best in relatively bright Light. The centre of the fovea is the foveola - about 0. 2 mm in diameter - where only cone photoreceptors are present and there are virtually no rods. Rod cells, or rods, are Photoreceptor cells in the Retina of the Eye that can function in less intense Light than can the other type ^[1]

Compared to the rest of the retina, the cones in the foveal pit have a smaller diameter and can therefore be more densely packed (in a hexagonal pattern). The vertebrate retina is a light sensitive part inside the inner layer of the Eye. Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees The high spatial density of cones accounts for the high visual acuity capability at the fovea. This is enhanced by the local absence of retinal blood vessels from the fovea, which, if present, would interfere with the passage of light striking the foveal cone mosaic. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 The absence of inner retinal cells from the foveae of primates is assumed to contribute further to the high acuity function of the fovea.

Since the retina does not have a blood supply, the fovea must receive oxygen from the vessels in the choroid, which is across the retinal pigment epithelium and Bruch's membrane. This is an article about the rock music band "Circulatory System" Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The choroid, also known as the choroidea or choroid coat, is the vascular layer of the Eye lying between the Retina and the Sclera The retinal pigment epithelium ( RPE) is the Pigmented cell layer just outside the neurosensory Retina that nourishes retinal visual cells and is firmly Bruch's membrane is the innermost layer of the Choroid. It is also called the vitreous lamina, because of its glassy microscopic appearance This blood supply alone does not satisfy the metabolic needs of the fovea under conditions of bright light, and the fovea thus exists in a state of hypoxia when under bright illumination. Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate

Since cones contain the pigmented opsins that allow humans to discriminate color, the fovea is largely responsible for the color vision in humans which is superior to that of most other mammals. Opsins are a group of light-sensitive 35-55 kDa membrane-bound G protein-coupled receptors of the Retinylidene protein family found in Photoreceptor cells Color vision is the capacity of an organism or machine to distinguish objects based on the Wavelengths (or frequencies) of the Light they reflect or emit Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands

The fovea comprises less than 1% of retinal size but takes up over 50% of the visual cortex in the brain. The term visual cortex refers to the primary visual cortex (also known as striate cortex or ^[5] The foveal pit is not located exactly on the optical axis, but is displaced about 4 to 8 degrees temporal to it. In Optics, the term optical axis is used to define a direction along which there is some degree of Rotational symmetry. The fovea sees only the central two degrees of the visual field, which is roughly equivalent to twice the width of your thumbnail at arm's length. ^[6]

Surrounding the foveal pit is the foveal rim, where the neurons displaced from the pit are located. This is the thickest part of the retina.

Since the fovea does not have rods, it is not sensitive to dim lights. Astronomers know this: in order to observe a dim star, they use averted vision, looking out of "the side of their eyes". Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena Averted vision is a controversial technique for viewing faint objects visually

The fovea is covered in a yellow pigment called xanthophyll,^[1] with the carotenoids zeaxanthin and lutein (Balashov and Bernstein, 1998), present in the cone axons of the Henle fibre layer. Xanthophylls (originally phylloxanthins) are yellow Pigments from the Carotenoid group Carotenoids are organic Pigments that are naturally occurring in Chromoplasts of plants and some other photosynthetic Organisms Zeaxanthin is one of the two Carotenoids contained within the Retina of the Eye. As a pigment This Xanthophyll, like its sister compound Zeaxanthin, has primarily been used as a natural colorant due to its Orange-red Color An axon or nerve fiber is a long slender projectionof a nerve cell or Neuron, that conducts electrical impulses away from the neuron's Cell ^[1] The pigment area absorbs blue light and is probably an evolutionary adaptation to the problem of chromatic aberration. eVolution is the third Album by eLDee, it was due to be released in 2008 In Optics, chromatic aberration is caused by a lens having a different Refractive index for different Wavelengths of Light

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 simians ( Infraorder Simiiformes) are the "higher Primates quot familiar to most people the Monkeys and the Apes including A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye 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 which elsewhere in the retina form more superficial layers having been displaced away from the foveal region during late fetal and early postnatal life. A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and Postnatal ( Latin for 'after birth' from post meaning "after" and natalis meaning "of birth" is the period beginning immediately after Other foveae may show only a reduced thickness in the inner cell layers, rather than an almost complete absence.

See also

• Eye movement
• Eye movement in language reading
• Eye movement in music reading
• Gaze-contingency paradigm
• Macular degeneration
• foveal system

References