The Human Eye And Their Parts
The Human Eye And Their Parts: The human eye is that part of the body that reacts to light for various purposes. The eye is the sense with which we can see. The human eye can differentiate between 10 million colors. The eyes are one of the main senses of the human body which helps in seeing the form and color of any nature.
Structure of The Human Eye
The structure of the eye is in the shape of a sphere. A ray of light coming from an object enters our eyes through the lens of the eye and forms an image on the retina. The retina is a kind of light-sensing screen located at the back of the eye. The retina, by the light-sensitive cells, sends the signals of light waves to the brain, and we are able to see the related object. Overall, seeing any object with the eyes is a complex process.
Eye Ball
The whole eye is in the form of an eyeball. The shape of the human eyeball is similar to that of a sphere and the diameter of the eyeball is approximately equal to 2.3 cm.
The eyeball has several parts:
Cornea
The cornea is a transparent thin membrane, and it forms a transparent bulge on the front surface of the eyeball. The ray of light coming from any object enters the eyes only through the clear circle or cornea. The clear circle or cornea covers the pupil, iris, and aqueous humor. The transparentness of the clean circle or cornea is a very important and important quality.
The cornea has no blood vessels and is fed by diffusion of lacrimal fluid from the outside and aqueous humor from within. Most of the refraction of light rays entering the eye occurs on the outer surface of the cornea.
Iris
The iris is a thin, circular, and dark-colored muscular diaphragm, located just behind the cornea. The iris controls the size of the pupil so that the right amount of light reaches the retina.
The color of the eyes of human beings is determined by the colors of the iris.
Pupil
A round hole-like pupil in the middle of the iris The pupil controls the rays of light entering the eye so that the right amount of light reaches the retina. The human pupil is spherical.
Lens
The lens of the eye (eye lens) is similar to other lenses. The eye consists of a transparent bi-convex lens, made of a fibrous jelly-like substance. This lens is located just below the iris. This lens refracts the rays of light coming from any object and creates its inverted and real image on the retina.
Retina
It is located in the back part of the eye. The retina is the back part of the eye. The retina is a microscopic membrane that contains a large number of light-sensitive cells. These light-sensitive cells generate electrical signals. The rays of light coming from an object after refraction by the eye lens form an image on the retina.
As soon as the image is formed on the retina, the light-sensitive cells present in it get illuminated and become active and generate electrical signals. This electrical signal travels through the visual nerves to the brain.
The brain interprets these signals and eventually processes this information so that we see an object as it is.
Power of Accommodation
The ability of the eye lens to adjust the focus distance is called the adjusting power of the eye.
In other words, the ability to increase or decrease the curvature (curvature of focus or focal length) of the eye lens in order to see the object placed at a particular distance call an accommodative power.
The lens of the eye is made of fibrous jelly, so it is flexible. The curvature of the lens can be modified to some extent by the ciliary muscles attached to the eye lens. A change in the curvature of the eye lens also changes the focal length of the lens.
And when the ciliary muscles contract or contract, the eye lens becomes thicker, and its curvature increases. As the curvature increases, the focal length of the lens decreases. Due to the decrease in the focal length of the eye lens, we are able to see close objects clearly.
But the adjusting power of the eye lens is only up to a certain limit. Because the focal length of the eye lens cannot be less than a certain limit. This is the minimum distance from the eye 25 cm.
Defects of Vision and their Correction
Sometimes the eyes gradually lose their ability to adjust, due to which the person is not able to see the objects clearly. Vision becomes blurry due to refractive defects in the eye, it is called eye defect.
There are mainly three types of eye defects caused by refractive defects:
(i) myopia,
(ii) hypermetropia and
(iii) presbyopia.
