Eye Anatomy : Working, Parts, Common Myths, Conditions, Treatments
The eye is a small yet multifaceted unit of anatomical machinery. Eye is the most complex organ of a human body. It shows the world to you. Vision occurs when light enters the eye through the pupil. The eye can be compared to a camera. They both receives light and transform it into a picture that we can interpret. It is the medium which processes 80% of the information received from the outside world. The anatomy of a eye is very important. Lets discuss in a brief how a human eye works.
How a Human Eye Works ?
To understand how the eye works, it is useful to think of a camera. The human eye is much more complex than a camera, but the working principles are almost similar.
Light reflects off from the object and enters the eyeball through the cornea, a transparent layer of tissue at the front of the eye. The cornea refracts or bends them through the dark opening in the center of the colored portion of the eye called pupil. The pupil appears to expand or contract based on the intensity of the light entering the eye. The adjusted light passes through the lens of the eye, which automatically adjusts the path of the light and brings it into sharp focus onto the retina, the receiving area at back of the eye. The retina converts the light rays into electrical impulses which travel through the optic nerve at the back of the eye to the brain, where an image is finally perceived.
The eye has many parts that must work together to produce clear vision: The sclera, or white part of the eye, protects the eyeball. The pupil, or black dot at the centre of the eye, is a hole through which light can enter the eye. The iris, or colored part of the eye, surrounds the pupil.
What is the eye made of ?
The eye is made up of three coats, enclosing three transparent structures. The outermost layer, known as the fibrous tunic, is composed of the cornea and sclera. The middle layer, known as the vascular tunic or uvea.
Parts Of The Eye :
1. Cornea – It is a transparent layer at the front of the eyeball which refracts the light entering the eye, which then focuses it onto the retina.
2. Iris – It is a ring of muscles within the colored portion of the eye that adjusts the pupil opening based on the intensity of light. So when a pupil appears to expand or contract, it is actually the iris doing its job.
3. Pupil – It is a circular opening in the centre of the iris through which light passes into the lens of the eye. The widening and narrowing of the pupil is controlled by iris.
4. Lens – It is a transparent structure located behind your pupil. It helps to refract incoming light and focus it onto the retina.
5. Choroid – the middle layer of the eye between the retina and the sclera.
6. Macula – a yellow spot on the retina at the back of the eye which surrounds the fovea.
7. Retina – membrane at the back of the eye that changes light into electric or nerve signals that our brain translates into image. The retina works much in the same way as film in a camera. The retina is made up by millions of specialised cells known as rods and cones. Rod cells are necessary for seeing in dim light, whereas cone cells are necessary for seeing in bright light. The human eye contains about 125 million rods and cone cells are between 6 – 7 million.
8. Optic nerve – It is formed from all the fine nerve fibers that originate from the photoreceptors in the retina, which form a cable-like bundle connecting the eye with the brain. The optic nerve carries electrical impulses from the macula and retina to the processing center of the brain where they are interpreted into clear, colorful sight.
9. Sclera – The white part of the eye, a covering with which the cornea forms the outside protective coat of the eye.
10. Vitreous Gel – it is a firm jelly that fills the space between the lens and the retina, and helps to support its internal structure. It is present at birth and remains unchanged throughout one’s life.
11. Rod cells are one of the two types of light-sensitive cells in the retina of the eye. There are about 125 million rods, which are necessary for seeing in dim light.
12. Cone cells are the second type of light sensitive cells in the retina of the eye. The human retina contains between six and seven million cones; they function best in bright light. They are very necessary for receiving a sharp accurate image. There are three types of cones, each sensitive to the wavelength of a different primary color – red, green or blue.
13. Macula – an area of the eye near the center of the retina where visual perception is most acute.
Common Myths For Vision Or Eye :
1.Eating carrots will make your vision better.
2. Reading in the dark will hurt your eyes.
3. You have to wait for a cataract to be “ripe” before having it removed.
4. 20/20 is perfect vision.
5. Eyes will hurt if you sit too close to the television set.
Eye Conditions : Explanation
1. Cataract – A clouding of the natural internal lens of the eye, which can cause blurred vision.
2. Hyperopia (farsightedness) – Inability to see near objects clearly. The eye is “too short” for the lens.
3. Myopia (nearsightedness) – Inability to see clearly at a distance. The eye is “too long” for the lens.
4. Diplopia (double vision) – Seeing double can be caused by many serious conditions. It requires immediate medical treatment.
5. Refraction – If vision is impaired, a series of lenses are placed before the eyes to determine the right corrective lens prescription.
Eye Treatments : Explanation
1. Cataract Surgery– The cloudy cataract is removed from the lens and replaced by a man made lens
2. Contact Lenses and Glasses- Glasses or contact lenses correct refractive errors such as nearsightedness, farsightedness.
3. Laser Photocoagulation– A doctor uses a laser to treat parts of the retina with poor circulation or to treat abnormal blood vessels directly
How many chambers are there in the eyeball ?
- The anterior chamber sits in front of the iris.
- The posterior chamber between the iris and the lens.
- The vitreous chamber lies behind the lens filling most of the eye.
Why don’t objects like contact lens and eyelashes get stuck behind the eye?
Because the conjunctiva covering the front of the eye loops forward and
covers the inside of the eyelids as well.
What is the Uvea ?
The uvea comprises the iris, ciliary body, and the choroid. They are all
connected to each other and are histologically similar.
How many layers are there in the cornea?
There are five:
- The superficial Epithelium
- Bowman’s layer
- Decemet’s membrane
- The inner Endothelium.
So, this was all about Eye anatomy. You can grab more details by reading the other articles related to eye on our blog to get more brief idea of a human eye.
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