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The '''eye''' is the organ of sight.  The eye enables creatures to perceive light in various ways, from simple lightness versus darkness, to full-fledged color vision.

The '''eye''' is the organ of sight.  The eye enables creatures to perceive light in various ways, from simple lightness versus darkness, to full-fledged color vision.

In the human, and most mammals, the eye consists of several structures.  The cornea is a protective outer layer.  The iris is an aperture through which light enters.  The lens is controlled by muscles to focus the light on the cornea - which is where the receptors for light are located.

In the human, and most mammals, the eye consists of several structures.  The cornea is a protective outer layer.  The iris is an aperture through which light enters.  The lens is controlled by muscles to focus the light on the retina at the back of the eye.

The cornea has many specialized nerve endings that are able to react to light and send their signals via the optic nerve to the brain for interpretation. There are receptors for subtle levels of light, which enable, at least, black and white vision in low-light environments. There are also receptors that repsondf to higher levels of light that can perceive color.

The retina has many specialized cells (photoreceptors) that are able to react to light and send their signals via the optic nerve to the brain for interpretation. There are two types of photoreceptor cell called rods and cones. Rods are by far the most numerous (around 120 million) and are sufficiently sensitive to allow basic black/white vision even at very low light levels. Cones (6-7 million) only function at higher light levels, but enable us to perceive colour. <ref>http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html</ref>

Typically eyes come in pairs, to allow binocular vision, which allows depth perception, but [[spider]]s (for example) have eight eyes, and [[scallop]]s may have several dozen.

Typically eyes come in pairs, to allow binocular vision and hence depth perception, but [[spider]]s (for example) have eight eyes, and [[scallop]]s may have several dozen.

== Diseases of the eye ==

== Diseases of the eye ==

[[Image:Eyeball.jpg|right|thumb|Doctors performing an eye surgery.]]

[[Image:Eyeball.jpg|right|thumb|Doctors performing eye surgery.]]

The eye worm ''Loa loa'', a [[parasitism|parasitic]] [[nematode]] worm, inhabits the vitreous humour of the human eyeball in parts of Africa, and is often only detected when somebody sees the worm swimming across inside the eyeball. [http://www.paru.cas.cz/helminti/Nematoda/Loa_loa.gif]

The eye worm ''Loa loa'', a [[parasitism|parasitic]] [[nematode]] worm, inhabits the vitreous humour of the human eyeball in parts of Africa, and is often only detected when somebody sees the worm swimming across inside the eyeball.<ref>http://www.paru.cas.cz/helminti/Nematoda/Loa_loa.gif</ref>

== Evolution of the eye ==

== Evolution of the eye ==

Numerous, unrelated organisms possess eyes of varying degrees of complexity. Evolutionists allege that these all evolved independantly to meet a common need; this is discussed in some detail in ''[[Climbing Mount Improbable]]'', by [[Richard Dawkins]]. [http://www.trueorigin.org/dawkrev2.asp]

Numerous, unrelated organisms possess eyes of varying degrees of complexity. Evolutionists allege that these all evolved independently to meet a common need; this is discussed in some detail in ''[[Climbing Mount Improbable]]'', by [[Richard Dawkins]]. <ref>http://www.trueorigin.org/dawkrev2.asp</ref>

Creationists commonly cite the necessary complexity of the eye, in order for it to offer even basic functionality, as clear evidence that it could not have arisen via an evolutionary process.

Creationists commonly argue that, in order to offer even basic functionality, the eye must be so complex as to preclude an evolutionary explanation for its development.

== Eyes in the Bible ==

== Eyes in the Bible ==

<blockquote>

<blockquote>

''And if any mischief follow, then thou shalt give life for life, Eye for eye, tooth for tooth, hand for hand, foot for foot, Burning for burning, wound for wound, stripe for stripe.'' Exodus 21:23-25

''And if any mischief follow, then thou shalt give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burning for burning, wound for wound, stripe for stripe.'' Exodus 21:23-25

</blockquote>

</blockquote>

''And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.'' Matthew 5:29

''And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.'' Matthew 5:29

</blockquote>

</blockquote>

[[Category:Anatomy]]

[[Category:Anatomy]]