Human Eye : Facts, Specifications, Resolution, How It Works ?
The human eye is really very fascinating, demonstrating the architectural wonders of the human body. It is the most complex organ in our body. It is our window to the world. It is the medium which processes 80% of the information received from the outside world. Just imagine trying to live without your vision!. It collects light and convert it into an electrical signal that our brain translates into images. The human eye can be compared to a camera which gathers, focuses, and transmits light through a lens to create an image of the environment. Well, many people wants to know how exactly a human eye works. Why it is called the most complex organ of the body. In this section, you will learn how a human eye works, human eye anatomy, its parts, facts related to human eye.
How a Human Eye Works ?
A human eye works like a camera. A camera gathers, focuses, and transmits light through a lens to create an image of the environment. Similarly, in a human eye, the image is created on the retina, a thin layer of light sensitive cells at the back of the eye. The lens of the eye or refracts light that enters the eye. The cornea also contributes to focusing light on the retina. Nerve fibers which are extending back from the retina’s nerve cells come together behind the retina to form the optic nerve. It connects the eye with the brain. Its purpose is to transmit messages like what we see, to the brain. The human eye can control the amount of light entering the eye through the lens.
The eye seems like an asymmetrical globe, about an inch in diameter. When we look into someone’s eyes we can see several structures. These different structure’s have different functions. The front part of the eye includes:
The Iris (the pigmented part) – The Iris is a colored circular muscle, which is beautifully pigmented and which gives color to our eye’s (the central aperture of the iris is the pupil). This circular muscle controls the size of the pupil so that more or less light ( depends on conditions) is allowed to enter the eye. The eye has a color due to variable amounts of eumelanin (brown/black melanins) and pheomelanin (red/yellow melanins) produced by melanocytes. The persons with more amount of eumelanin are brown eyed and those with pheomelanin have blue and green-eyes.
The Cornea (a clear dome over the iris) – The cornea is a transparent external surface, that covers both the pupil and the iris. It is the first and most powerful lens of the optical system of the eye. Cornea along with the crystalline lens allows the production of a sharp image at the retinal photoreceptor level.
The Pupil (the black circular opening in the iris that lets light in) – Pupil is a black-looking aperture, that allows light to enter the eye. It seems darker in color because of the absorption of pigments in the retina.
The Cclera (the white part) – The sclera is called as “white part of the eye”. This forms part of the supporting wall of the eyeball. This part is continuous with the cornea and further adds to the external covering of the eye is in continuity with the dura of the central nervous system.
The conjunctiva (a thin layer of tissue covering the front of the eye, except the cornea)
Optic Nerve– It is formed from all the fine nerve fibers that originate from the photo receptors in the retina, which form a cable-like bundle connecting the eye with the brain.
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.
Ciliary Body– It is a muscle which helps to change the shape of the lens to allow for focusing.
Human Eye Resolution :
When you buy a mobile phone or camera, the first question that comes to your mind is what is its camera resolution. But, have you ever wondered how many megapixels is the human eye? The eye is not a single frame snapshot camera. It is more like a video stream. And, it will be surprised to know that a human eye is 576 megapixels.
Here we have shown some facts so that human eye specifications are more clear to you. Just read the list below :
Human Eye Specifications (Typical)
Sensor (Retina) : 22mm diameter x 0.5mm thick (section); 10 layers
Resolution : 576MP equiv.
Visual Acuity : ~ 74 MP (Megapixels) (printed) to show detail at the limits of human visual acuity
ISO : 1 – 800 equivalent
Data Rate : 500,000 bits per second without colour or around 600,000 bits per second including colour.
Lens : 2 lenses – 16mm & 24mm diameter
Dynamic Range : Static : contrast ratio of around 100:1 (about 6 1/2 f-stops) (4 seconds)
Dynamic Range : Dynamic : contrast ratio of about 1,000,000:1 (about 20 f-stops) (30 minutes)
Focal Length : ~ 3.2mm – (~ 22mm 35mm equiv)
Aperture : f2.1 – f8.3 (f3.5 dark-adapted is claimed by the astronomical community)
FOV Field of View : 95° Out, 75° Down, 60° In, 60° Up
Color Space : 3D (non-linear) RGB
Color Sensitivity : 10,000,000 (ten million)
Color Range : 380 to 740 nm
White Balance : Automatic (constant perceived color under different lighting)
Refresh Rate : Foveal vision (high-quality telescopic) – 3-4fps; peripheral vision (very inaccurate) – up to 90fps
Human Eye Color :
Eye color is a polygenic phenotypic character. It is determined by two factors: the pigmentation of the eye’s iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris.
The pigmentation of the iris varies from light brown to black in human. This variation depends on the concentration of melanin in the iris pigment epithelium (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma. The appearance of various colors in eyes like, blue and green, as well as hazel eyes, are results from the Tyndall scattering of light in the stroma, a phenomenon similar to that which accounts for the blueness of the sky called Rayleigh scattering. The human iris do not consist of any of the two colors neither blue nor green.
Eye color is usually determined by variations in a person’s genes. Most of the genes associated with eye color are involved in the production, storage of a pigment called melanin. Eye color is directly related to the amount and quality of melanin in the front layers of the iris. People who have a large amount of melanin in the iris, have brown eyes, while people with blue eyes have much less of this pigment.
Human Eye Facts :
1. Your retinas actually perceive the outside world as upside-down – your brain flips the image for you.
2. Your eyes can get sunburned. That’s why it is important to wear sunglasses to protect your eyes from UV rays.
3. Your peripheral vision is very low-resolution and is almost in black-and-white.
4. On average, you blink 17 times a minute.
5. A “20/20 vision” doesn’t mean you have a perfect vision. It just means you can see 20 feet in front of you as well as the average person can.
6. If you have shortsightedness, your eyeball is longer than normal. And, If you have farsightedness then, it’s shorter than average.
7. 80% of sensory information our brains receive is through our eyes.
8. The eye muscle contracts in less than 1/100th of a second. That’s why It is the fastest reacting muscle in the body.
9. On average, the human eye can detect more than 10 million colors.
10. Your eyelashes keep foreign particles, like dirt, out of your eyes.
We hope that we have provided you sufficient information about eyes. If you feel anything important is still missing you can comment on the box below. Your comments will be highly appreciated. For more information regarding various health topics we suggest you to stay tuned to Helpsutra as we are here for your help.