STRUCTURE AND FUNCTION OF THE HUMAN EYE
The human eyes are the most complicated sense organs in the human body. From the muscles
and tissues to nerves and blood vessels, every part of the human eye is responsible for a
certain action. And contrary to popular belief, the eye is not perfectly spherical; instead, it is
two separate segments fused together. It is made up of several muscles and tissues that come
together to form a roughly spherical structure. From an anatomical perspective, the human
eye can be broadly classified into the external structure and internal structure.
The External Structure of an Eye
The parts of the eye that are visible externally comprise the external structure of the eye.
These include the following:-
1. Sclera: It is a tough and thick white sheath that protects the inner parts of the eye. We
know it as the ‘White of the eye’.
2. Conjunctiva: It is a thin transparent membrane that is spread across the sclera. It
keeps the eyes moist and clear by secreting small amounts of mucus and tears.
3. Cornea: It is the transparent layer of skin that is spread over the pupil and the iris.
The main role of the cornea is to refract the light that enters the eyes.
4. Iris: It is a pigmented layer of tissues that make up the coloured portion of the eye. Its
primary function is to control the size of the pupil, depending on the amount of light
entering it.
5. Pupil: It is the small opening located in the middle of the Iris. It allows light to come
in.
The Internal Structure of an Eye
The internal structure of the eye includes the following parts:
1. Lens: It is a transparent, biconvex, and an adjustable part of an eye. The lens with the
help of the cornea refracts light focused on the retina, therefore creating images on it.
2. Retina: It is the layer present at the back of the eye where all the images are formed.
It is the third and inner coat of the eye which is very sensitive towards the light
