The eyes are the organs of the visual system. They provide visions to the bodies, the ability to receive and process visual details, and also enable several photo response functions that are independent of the vision. The eyes detect light and transform it into electrochemical impulses in neurons.


In elevated organisms, the eye is a complicated optical system that collects light from the surrounding environment, regulates its intensity through the diaphragm, focuses it through an adjustable set of lenses to create an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex pathways nerves that connect the eye through the optical nerve to the eye cortex and other areas of the brain. Eyes with resolved force have ten essentially different forms, and 96% of animal species have a complex optical system. Eyes that dissolve the image are present in mollusks, stringers, and arthropods. Read below Eye functions


Eye functions


For people with normal functioning eyes the following sequence takes place:

Light reflects from the object we look at.
Rays of light penetrate the eye through the cornea at the front of the eye.
The light passes through the aqueous fluid (water humor) and enters the pupil to reach the lens.
The lens can change the thickness to bend the light that focuses it on the retina at the back of the eye.
On the way to the retina, the light passes through a dense, transparent liquid called glassy humor. The vitreous body fills the eyeball and helps to keep it around.
The light reaches the back of the eye and hits the retina. The retina transforms the light into electrical impulses, which transmits to the brain with the optic nerve.
Finally, the visual cortex interprets these impulses as what we see.



What is the normal vision


To understand the vision of a person with a visual impairment, it may be helpful to know the correct vision. Imagine a scenario in which two people are sitting on the couch in front of you. If you look directly at Person A, you will be able to use your spot or central vision to see the details of their head and face. Maybe they have freckles, brown eyes, and black hair.


At the same time, you realize that Person B is sitting on the couch next to Person A. However, you can not see the same amount of detail on your face. For example, you can only see the dark areas in which their eyes are. To see Person B, you use the rest of your retina or peripheral vision. Seeing clearly and sharply in the center, and blurred at the periphery is considered the normal vision.



Sight problems


A problem with any part of the eye can cause eye problems. There are many types of eye diseases that can affect the eye functions in different ways. In some cases, the lens does not focus properly, or the shape of the eyeball is not round, so the picture appears indistinct. Often this can be improved by using corrective glasses or contact lenses. When the image is focused behind the retina, this is called hyperopia. When the image focus against the retina, this refers to myopia (myopia).


Some eye conditions affect the retina. For some people, this only applies to their peripheral vision, which may cause vision in the tunnel. In the case of other people, this only affects their vision of the macula, which can lead to the formation of dead spots. Finally, other eye conditions that can cause vision problems to eye functions include clouding of the lens (cataract), increased pressure in the eye (glaucoma), corneal damage or problems with the eye muscles.

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