A more detailed description of the eye and it's functions.
Visual organ (organum visus) / Introduction
Sight is one of the most important sensory perceptions, enabling human beings to orientate themselves within their surroundings.
The eyes (oculi) enable shapes and colors, light and dark to be distinguished by means of light impulses. Vision is a result of these light impulses being processed in the brain (cerebrum). This highly developed form of sensory perception is primarily achieved when supported by the
memory. Vision is facilitated by a physical process: a refraction of light when it penetrates materials of varying optic density.
If the ray of light falls on a transparent material, it alters its direction.
A particular shape can cause the ray of light to bundle or scatter. This fact is exploited in a camera, for example, and vision is often explained by comparing it to the way a camera works: the lens in the eye corresponds to the lens in the camera, the pupil corresponds to the aperture, and the retina to the film. In a camera, a small, reverse image appears via the lens on the film. In the eye, this image appears on the retina.
In the visual organ (organum visus), the sensory cells are equipped with auxiliaries and constitute a complicated visual apparatus: in the eyeball (bulbus oculi), optic stimuli are converted to neural activity. A n ingenious system of nervous fibers then transports these stimuli to the brain. With the help of the ocular muscles (musculi bulbi), the eyeball (bulbus oculi) can be moved. Two-eyed vision (binocular vision) in one image becomes possible and the field of vision can be extended. The eyeball is protected by the eyelids, eyelashes, lacrimal glands and eyebrows.
The light-refracting part of the eye is composed of the cornea, aqueous humor, the lens and the vitreous body.
The rays of light hitting the eye from the outside are united to form one image through the light-refracting part of the eye.
In order for this to happen, the rays of light are converted to nervous stimuli, which then travel to the optic center in the brain (cerebrum) and enter conscious thought as an image.
In order to see an image clearly, we involuntarily direct our eyes towards the object in question so that its image is projected onto the fovea centralis or "yellow spot", the point of clearest vision. The further from the "yellow spot" objects are displayed, the more unclear they become. At the point where the optic nerve (nervus opticus) leaves the eye, we cannot see anything at all, and this point is therefore known as the "blind spot".
In order to adapt to different distances of vision, the lens can bend to varying degrees. This process of distance adjustment is called accommodation and is carried out with the help of the ciliary muscle. When the eye has to be adjusted for seeing far distances, the ligaments around the lens pull it from all sides and flatten it.
To see near distances, a sphincter muscle containing ciliary bodies contracts, thereby relaxing the suspensory apparatus of the lens. Due to its elasticity, the lens then bends even further, until the object is clearly displayed on the retina. This tension of the ciliary muscle causes the eye to tire more rapidly when required to look at near distances than far ones.
In addition to accommodation, focusing is supported by the ability of the pupil to narrow as the lens becomes more bent.
It should be noted that these processes usually take place in both eyes (binocular). In order to avoid "seeing double" (diplopia), the brain (cerebrum) is capable of fusing the two images.
7 questions evolutionists can't answer:
1) In the evolution of the eye. Which evolved first. A) The eye itself, or B) The vision center of the brain?
2) In the evolution of the eye, how long did it take before it became a funtional organ (in other words, how long was the eye useless, which made us blind)?
3) Which evolved first? The eye, or the muscles that hold it in place, and control it?
4) When we finally where able to use this organ, where we able to see in almost real time as we do now? Or did the vision center of our brain have to evolve more to process the information the eye was sending to it?
5) Did we see in color, or black and white?
6) In what sequence did the parts of the eye evolve (link)? There are over 40 parts that all have to work together for the eye to function properly.
7) Some parts of the eye are not found in any other part of the human body. How did natural selection devise all this to come together for this organ to work?