In this article we will discuss about the structure of human eye with the help of suitable diagram.
The human eye is a very sensitive and delicate organ suspended in the eye socket which protects it from injuries. It essentially consists of CORNEA, LENS & RETINA besides many other parts such as Iris, Pupil and aqueous humour, vituous humour etc. Each one has got a specific function.
A section of the eye is as shown in Fig. 2.2.
The functions of various parts are described below in brief:
1. Cornea:
It is a translucent membrane which covers the visible portion of eye. The black (as brown, blue or any other shade) portion is Iris that is visible through cornea. Iris is perforated and the perforation is knows as pupil.
2. Lens:
The lens is visible through the pupil. It is a colourless double convex crystalline lens which divides eyeball into two chambers, one of which contains a fluid known as aqueous humour and the other has vitreous humour. The lens forms an inverted real image on Retina.
3. Retina:
It is the sensitive portion on which the image of the thing which we see is formed.
It consists of two types of nerve cells viz.
a. Rod cells and
b. Cone cells.
The rod cells function during dim light such as moonlight and cone cells function during bright light. Human eye contains many cone cells and a few rod cells. The retina is connected to brain through optic nerve. The cone cells are colour sensitive.
4. Optic Nerve:
This nerve transmits the sensation to the brain and helps us to visualise the object.
In order to protect the eye from dust, dirt and small objects, two eyelids are provided, one on top and the other below. Both may close at any moment.