The incredible human eye| HUMAN EYE | Function of eye

 

The incredible human eye

We known that importance our eye. It can help us to sensation of vision. It is one of the most sensitive and important organ to all living beings. Vision helps us to detect desired targets, threats, and changed in our physical environment and to adapt accordingly. So, let us known more details about human eye.

Structure of human eye:

Our eye contains eye lids, eye lashes, eye brows and lachrymal glands. A thin layer, called conjunctiva covers the front portion of eye. Only 1/6 portion of the eye  ball is visible to us. The eye ball is located in the eye socket. Eye has 3 main layers.

·        Sclerotic layer  or sclera

·        Choroid layer

·        Retina

The outer most thick, tough, fibrous, non-elastic and white coloured layer is sclera. The sclera bulges and forms cornea. The end of sclera connects to the optic nerve. The second layer is choroid layer. This layer is Black in  colour and contains a lot of blood vessels. It encloses the eye except the part formed by the choroid layer around the pupil is iris. Radial and circular muscles are present in the iris. Biconvex lens is present immadtely behind the pupil is attached to ciliary muscles and suspensory ligaments.

The lens divides the inner space of the eye ball as aqueous chamber and vitreous chamber. Aqueous chamber is filled with jelly like fluid .

Retina contains the cells, called rods and cones. The area of no vision, called blind spot and the area of the best vision,  called yellow spot  are present in the retina. The yellow spot is also known as Macula or fovea.

 

Functioning of the eye:

            The vision sensation

You might think of the eye as a sort of video camera that the brain uses to make motion pictures of the world. Like a camera, the eye gathers light through a convex lens, focuses it, and forms an image in the retina at the back of the eye. The lens, turns the image left to right and upside down . This vision reversal may have influenced the very structure of the brain, which tends to maintain this reversal in its sensory processing regions. Thus, most information from the sense organs crosses over to the opposite side of the brain. Like, maps of the body in the brain’s sensory areas are typically reversed and inverted. But while digital camera simply forms an electronic image, the eye forms an image that gets extensive further processing IN the brain.

The unique characteristic of the eye that make it different from other organs, lies in its ability to take the information from the light waves then transform the characteristics of the light into neural signals that the brain can process. This happens in the retina, the light-sensitive layer of cells at the back of the eye that acts much like the light-sensitive chip in a digital camera, things can go wrong. For example ,the lenses of those who are nearsighted focus image short of ( infront) of the retina, in those who are far sighted the focal point extends behind the retina. Either way, images are not sharp without corrective lenses.

Receptor cells of the eye:

The real work in the retina is performed by light – sensitive cells known as PHOTORECEPTORS. These photoreceptor’s of colour. Making the fine distinction necessary for colour vision is the job of the nearly 7 million cones containing the pigment IODOPSIN that come into play in brighter light. Each cone is specialized to detect the light waves we sense either as blue, red or consist of two different types of specialized cells the rods and cones that absorb light energy and respond by creating nerve impulses.

Our eyes function sometimes in near darkness and sometimes in bright light. These two types of processors involving distinct receptor cell types named for their shape have evolved for this purpose. Nearly 125 million tiny  rods containing  the pigment rhodopsin see in the dark that at night, that is they detect low intensities of light at night, through they cannot make the fine distinctions that give rise to our sensations yellow and the array of colours  formed by their combination. Thus the yellow field, the bright red morning sun, the blue sky and all other colours in nature are sensed.

The cones concentrate most in the very center of the retina, in the retina, in a small region called the fovea, which gives us our sharpest vision. With movement of our eye balls, we use the fovea to scan whatever interests us visually, the features of a face or a flower.

There are other types of cells in the retina that do not respond directly to light. These handle the job of collecting impulses from many photoreceptors ( rods and cones) and shuttling them on to the nerve cells. Presence of some other receptor cells sensitive to edges and boundaries of objects and those that respond to light and shadow. Bundled together, the nerve cells make up the optic nerve, which transport visual information from the eye to the brain.

So, this is the amazing structure  and the function of human eye. I hope you people have understand my article. I think it’s using to you. Thank you