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Anatomy of the Eye |
The most sensitive and valuable sense organ of the human body is the Human Eye. It is like a camera and it is based on the lens system. Study of eyes and eye diseases are known as Ophthalmology.
The Parts Of Human Eye And Its Functions
1)Cornea :- A thin membrane covering of surface of eyeball, through which light enters into the eye. It act as primary lens.
2) Iris :- Curtain like partition behind the cornea. It controll the size of pupil.
3) Pupil :- The black opening between the aqueous humour and the eye lens.
4) Ciliary muscles :- It controls the focal length of the eye lens and hold the lens in right position. Due to relaxation of these muscles focal length of the lens increase. When these muscles contact focal length of the lens decrease.
5) Crystalline lens :- The eye lens is a transparent, crystalline and double convex lens. Mode of transparent and flexible tissues. focuses the incoming light rays from the object on the retina to form real and inverted images.
6) Retina :- A delicate membrane having enormous number of light sensitive cells. Act like a screen on which image of object are formed.
7) Optic Nerves :- It is formed by the nerve fibres attached with retina. It carry nerve impulses or signals to the brain.
8) Aqueous humour :- It is transparent liquid filled behind the cornea. It secreted by Ciliary body.
9) Vitreous humour :- The jelly like substance filled between the eye lens and retina. It keep retina in place by pressing it against choroid.
Function Of The Eye
When a person looks towards any object, a reflected light from the object enters the pupil of the eye and falls on the eye lens (convex lens) which forms real and inverted image on the retina of the eye that consists of some special cells in the shape of rods and cones. Such special cells transform light energy in the form of signals for the brain. These signals reach to the brain by optic nerve. At last, the brain interpreters these signals and the person is able to see the object.
Power Of Accommodation
• The focal length of the lens increases if it's thickness decreases.
• The focal length decreases, the thickness of the lens increases
• The ability of an eye to focus the distant object as well as nearby objects on the retina by changing the focal length of the eye lens is known as accommodation of the eye.
• For normal eye - Far point ( infinity)
For distant object ~ Ciliary muscles relax ~ Eye lens becomes thin ~ Increase in
focal length.
• For normal eye - Near point (25 cm)
For nearly objects ~ Ciliary muscles contract ~ Eye lens becomes thick ~ decrease in focal length
Eye Diseases
•Short sight is also known as Myopia. When a person suffers from myopia he cannot see distant objects clearly since the image is formed - in front of the retina. Myopia can be corrected with concave lenses.
• Long site is called Hypermetropia. A person with hypermetropia cannot see nearby objects clearly. In hypermetropia image is formed behind the retina. Hypermetropia can be corrected with Convex lenses.
• Presbyopia is caused by the reduction in the elasticity of lens.
• In Astigmatism, curvature of cornea become irregular and image is not clearly formed.
• Squint eye can be corrected by Eye surgery.
• Colour blindness is a hereditary disease. Colour blindness is also known as Daltonism. Colour blindness was discovered by John Dalton. A person suffering from colour blindness is unable to distinguish red and green colour.
• Eye diseases that occurs due to the deficiency of Vitamin A
Night blindness, Xerophthalmia
• The loss of vision during dim light is called - Night blindness.
• Disease that occurs when iris becomes dry and opaque is called - Xerophthalmia.
• Clouding of eyes due to ageing - Cataract.
• Eye disease due to the increased pressure in the eye ball - Glaucoma. The drug used in treatment of glaucoma is Physostigmine.
• A condition in which eyes are not properly aligned and they are pointed to different direction is called Strabismus. It is also known as Heterotropia (or crossed eyes).
• Eye disease caused by bacterium Chlamydia trachomatis - Trachoma.
• An inflammation or infection of the conjunctiva us called Conjunctivitis ( also called red eye or madras eye)
The human eye is an amazing organ that plays a critical role in allowing us to see and interpret the world around us. It is a complex optical system that is capable of detecting a wide range of colors, adjusting to changes in lighting conditions, and focusing on objects at different distances. The eye works in conjunction with the brain to create a sense of depth, perspective, and motion, making it possible for us to navigate our environment and perform a wide range of tasks. Understanding the anatomy and function of the human eye is important for maintaining good eye health and preventing vision problems.
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