Human Eye

Human eye is one of the most beautiful and complex human organs. This is used to see various objects. The eye allows us to see the beautiful world around us. It allows us to see various colors, visualize various objects, and help to identify various objects around us. We can compare the human eye to the camera that we see in our daily lives on our phones, laptops, tablets, and others.

Human eye can be called the living camera that transfers information about our surroundings to the brain so our brain can process this information and allow us to see the surroundings. In this article, we will learn about the human eye, its structure, its workings, and others in detail.

Human Eye

Human eye is the most significant organ of our body. It enables us to see various objects and allows us to gather various information about all the objects around us. We see the world around us through our eyes. The light from various objects reaches our eyes and then our eyes transfer the information from the light to the brain and then the brain forms the image of the object around us.

The human eye can be compared to a camera which allows light to pass through its sensor and forms the image. The human eye is a spherical ball of diameter 2.3 cm and is filled with some fluid. The size of eyeballs in all humans is almost fixed but can vary marginally.

Structure of Human Eye

The human eye is a spherical structure of diameter 2.3 cm and there is some fluid filled inside the eye. It is connected to the human skull through some muscles that allow the eyeball to move freely inside the eye cavity. The eye cavity is protected from the outside by the eyelid which provides the required protection to the eyes from foreign particles.

There are various parts of the human eye that are discussed below in the article.

Parts of the Eye

The human eye is made up of various parts and all of the parts of the human eye are discussed below.

Vitreous Chamber: The inner volume of the eyeball where the eyeball is placed is called the Vitreous chamber. It maintains the proper pressure within the eye.

Sclera: The outer covering of the eyeball acts as a protective covering and is called the sclera. It is the white part of the eyeball.

Cornea: The part of the eye through which the light enters the eyeball is called the cornea. It is the front part of the Sclera.

Iris: The dark ring-like structure of the eye inside the cornea is called the Iris of the eye. It is the part that provides colour to the eyes and it helps the brain to adjust the exposure of the light entering the eyes.

Pupil: The pupil is a small opening in the Iris that allows the entry of light inside the eyeball. It is controlled by the Iris.

Lens: The lens is actually a lens made of muscles that is placed behind the iris that allows light to converge on the specific point inside the eye to form the image. The lens can adjust its focal length to allow light from all the sources to converge accordingly.

Retina: The light-sensitive layer at the end of the eyeball, where the light ray meets and the image is formed in the retina of the eye and the retina converts this image into electrical impulses that are then sent to the brain.

Optic Nerves: A nerve connected to the retina that transfers all the electrical information to the human brain is called the Optic Nerve. There are two types of optic nerves,

• Rods: These are the nerve cell that helps in peripheral vision and it is sensitive to even low light.
• Cones: These are the nerve cell that is used in visualizing various colors and are more sensitive to bright light.

Working of the Human Eye

Human eye is a sensory organ that allows us to see by gathering information from the light. It can be compared to the camera and its working is as follows,

• The light first enters the eye from the cornea.
• The intensity of the light is then adjusted by the Irisis by changing the size of the pupil.
• It is then focused in the eye lens, which focuses it to meet at the retina of the eye.
• Then the image is formed on the retina where rod cells and cone cells capture all the information about the object.
• The optic nerve then transfers all this information to the brain which then forms the image of the object.

And thus, we see the environment around us.

Function of Human Eye

The eye is a sensory organ that allows light from various objects to fall on its retina and then forms the image of that object. The lens of the eye adjusts automatically to allow the light to properly converge on the retina and then the image formed on the retina is converted to electrical impulses that are transferred to the human brain for further processing through optic nerves.

The amount of light entering the human eye is controlled by the iris and the cornea. The space inside the eyeball is filled with aqueous humor and vitreous humor which allow light to get refracted and meet at the fixed focal point on the retina.

Range of Vision of Human Eye

The human eye is a very incredible instrument that allows us to see at infinite distances till the light from that object can reach our eyes. Thus the far range of the human eye is infinity. We see the stars in the night sky that are very far away from us and the light from them reaches our eyes and thus we see them.

For the near point of the eye, it is the point till which the human eye can see distinctly and the near point of the human eye is, 25 cm, i.e. any object till 25 cm can be distinctly viewed by the human eye.

Lens of Eye

A lens placed behind the cornea of the human eye is called the eye lens. It is an optical lens made of proteins and other organic materials. It is situated exactly behind the Iris that allow light to pass through the lens and the eye lens then converges the light to the Retina of the eye.

It is ellipsoidal in shape and is roughly 10 mm long and 4 mm wide. It is made up of translucent protein molecule and thus allow light to pass through it.

Defects in Eyes

There are various defects that develop in our eyes because of aging or carelessness. Some of them are mentioned below:

• Myopia
• Hypermetropia
• Presbyopia
• Cataract
• Glaucoma
• Astigmatism

Myopia

Cause: Due to a strong refractive index of the eye or elongation of the eyeball

Correction: Shortsightedness is corrected by employing a biconcave (curved inwards) lens that is placed ahead of a myopic eye, moving the image back to the tissue layer and creating it clearer. Hyperopia is corrected by employing a convex (outward-facing) lens.

Hypermetropia (Hyperopia)

Cause: Due to a weak refractive index of the eye or contraction of the eyeball

Correction: Hyperopia will simply be corrected by sporting glasses with connection lenses or contact lenses. Notwithstanding that the degree of ametropia is tiny, correction remains recommended to forestall secondary issues like headaches or eye irritation

Presbyopia

Cause: Solidification of lens fluid

Correction: To correct this defect, someone is prescribed a central lens that has each style of lens convex and concave.

Cataract

Cause: Protein structures of the lens clubbed together

Correction: Cataract surgery involves removing the clouded lens and substituting it with a transparent artificial lens. The unreal lens, known as the associate in the nursing lens, is positioned within the same place as your natural lens. It remains a permanent part of your eye.

Glaucoma

Cause: Abnormal pressure inside the eye

Correction: Glaucoma is treated by lowering your eye pressure (intraocular pressure). Betting on your state of affairs, your choices could embody prescription eye drops, oral medications, optical device treatment, surgery, or a mix of any of those.

Astigmatism

Cause: Non-uniform curvature of the cornea

Correction: Astigmatism correction nowadays relies on the employment of special toric contact lenses. Astigmatism can even be corrected by reshaping the membrane through LASIK (laser in place keratomileusis) or PRK (photorefractive keratectomy). PRK removes tissue from the superficial and inner layers of the membrane. LASIK removes tissue solely from the inner layer of the membrane.

Care of Eyes

As the eye is one of the most important sensory organs and it is the most delicate one. One must take care of eyes regularly and the steps that should be used are,

• One has to be compelled to prefer an Associate in Nursing for everyday eye check-ups.
• Wear spectacles if the modality is found weak.
• Invariably study or watch TV in good lightweight. Excess or low light can end in problems. Low light can cause strain and winds up in a very severe headache.
• Do not examine the sharp provider of sunshine a bit like the sun directly. Excess lightweight can injure the eyes.
• If mud enters into the eye one should not rub them and rather wash them right away.
• Maintain a regular distance while reading or observing TV.
• Take a diet to form certain that you simply get the right nutrients.

Night Blindness

Night blindness conjointly referred to as visual disorder could be a defect within the vision within which individuals cannot read things properly in dim lightweight or at midnight. It mainly happens because of the lack of vitamin A in our body. Thus, always take foods that area unit made of vitamin A like broccoli, inexperienced vegetables, carrot, milk, eggs, curd, papaya, mango, etc.

How do Visually Impaired individuals Read and Write?

A visually impaired person is a person that can not see clearly. So reading and writing through normal means is very difficult for them. We can treat their eyes and they can get back their vision and can read normally and if it is impossible for them to get back their vision they can use the Braille system designed for Blind people to read and write.

Braille System

Braille system is a system developed by Louis Braille for the visually impaired person to read and write. In this system, we arrange dots on paper such that their impression can be felt by the touch. And various dots are used to represent various symbols in this system.

Formula Used

Power of Eye Lens Formula,

• P = 1/f (when f is in m)
• P = 100/f (when f is in cm)

Lens Formula,

1/v – 1/u = 1/f

where,

• v is distance of image
• u is distance of object
• f is focal length of lens

Read More,

• Reflection of Light
• Refraction of Light
• Diffraction of light

Numerical Problems on Human Eye

Problem 1. If the power of lens is 0.55 D. Find the focal length and type of the lens.

Solution:

Given,

• P = 0.55 D

Power of Lens(P) = 1/f

0.55 = 1/f

f = 1/0.55 = 1.8182 m

The focal length is 1.8182 m (+ve), hence the lens is convex lens.

Problem 2. If the focal length of lens is -2.6 m. Find the power of lens and type of the lens.

Solution:

Given,

• f = -2.6 m

Power of Lens(P) = 1/f

P = 1/(-2.6) = -0.384615 D

The Power of Lens is -0.384615 D (-ve), hence the lens is concave lens.

Problem 3: A person cannot see objects clearly beyond 80 cm. What is the power of the lens used?

Solution:

Given,

• v = -80 cm
• u = ∞

1/f = 1/v – 1/u

1/f = 1/(-80) – 1/∞ = -1/80

f = -80 cm = -.8 m

Power of lens(P) = 1/(-.8) = -12.5 D

Problem 4: A person wearing a convex lens of focal length 60 cm what is the power of length.

Solution:

Given,

• f = 60 cm

P = 100/f = 100/60

P = 1.66 D

This, the power of lens is 1.66 D

FAQs on Human Eye

1. What is the Function of Our Eyes?

Eye is the sensary organ that allow us to see.

2. What are Parts of Eye?

Various parts of Eyes are,

• Sclera
• Cornea
• Iris
• Pupil
• Lens
• Retina
• Optic nerves

3. What is a Blind Spot?

At the junction of the retina and the optic nerve, there are no sensory nerve cells and if the light ray falls on that point no image is formed. This junction point is called the Blind Spot.

4. What are Lens?

A transparent optical instrument that allows light to pass through it is called the lens. It is used to converge or diverge the light at a point. The human eye also has a lens.

5. What are Types of Optic Nerves?

The optic nerve carries information from the retina to the brain. They are of two types,

• Cones
• Rods

6. What is Eye Disease Called?

Some Eyes disases are,

• Cataract
• Myopia
• Hypermetropia
• Astigmatism

7. Do Human Eyes Grow with Age?

No, the human eye does not grow after the birth of the child.

8. What is Range of Vision of Human Eye?

The range of the human eye is,

• Far Range of Human Eye: Infinity
• Near Range of Human Eye: 25 cm