Mechanism of Sight
Even now as you read this book you are concerned with eyes and are completely aware of their value and existence. But perhaps till now you have not rightly thought about the construction of this small but complex and delicate organ of sight. The eye is one of the most beautiful and amazing signs of Almighty Allah; such that by studying it and pondering on the process of its creation, it is possible to discover the existence of the wise and powerful God, who is the creator of the world; and to become cognizant of the unlimited aspects of knowledge and power. There are so many amazing aspects of the human eye that it is not possible to mention all of them in this book. But we shall indicate some of them here. First of all let us become aware of the structure of the eye ball and after that we can take up the discussion of knowing God.
Structure of the eye
The eye ball is the real instrument of seeing, which works like a camera – on the contrary more complex than a camera. The eye ball is made up of three layers: sclera, choroids and retina.
1. What is the Sclera? It is a veil which is hard, firm, white and turbid and is approximately one millimeter thick. It covers the complete eye ball and protects it. Front of this sheet (sclera) is transparent in order to allow light to enter the eye. It is known as the cornea.
2. What is the Choroid? It is a thin and black curtain inside the sclera and which changes the interior of the eye into a dark chamber. Inside the choroid are a large number of blood veins which supply nutrition to eye structures and in fact choroids is also the food giving layer of the eye. The front portion of the choroid is in the form of a circular curtain fixed behind the cornea and which is known as iris.
There is an aperture in the center of iris, three to six millimeters in diameter and it is known as the pupil. The pupil automatically enlarges and contracts to regulate light entering the eye.
3. What is the retina? Retina is innermost sensitive layer of the eye. Images of bodies which come before the eye fall upon this curtain; the inner surface of the retina is the first colored layer. A jelly like substance called vitreous humor fills the space between lens and retina. The lens, iris and cornea are nourished by a clear fluid, aqueous humor, formed by the ciliary body and which fills the space between lens and cornea. Two types of receptors – rods and cones – are present. Rods are mainly found in the peripheral retina and enable us to see in dim light and to detect peripheral motion. They are primarily responsible for night vision and visual orientation. Cones are principally found in the central retina and provide detailed vision for such tasks as reading or distinguishing distant objects. They also are necessary for color detection. These photoreceptors convert light to electrochemical impulses that are transmitted via the nerves to the brain. Rods are approximately 120 million and cones are five million in number.
The fluid flows from ciliary body to the pupil and is absorbed through the channels in the angle of anterior chamber. The delicate balance of aqueous production and absorption controls pressure within the eye. Optical nerves connect the retina to the brain.
Yellow spot – at the rear of the eyeball there is a depression on the retina wall ellipse in shape and it is one millimeter in diameter and called as the Yellow spot. The Yellow spot is exactly in line of the pupil and it focuses the light that falls on it. Yellow spot is a part of retina and is its most sensitive portion and conical cells are compressed here in concentration and each of them is connected through a nerve to the center of sight in the brain. In order to see bodies clearly, our eyes automatically circle the surface of that body whose image falls on the Yellow spot.
Transparent mantles of the eyeball
Transparent mantles of the eyeball are parts which allow light to pass through them and which focus on the surface of retina. These transparent mantles are as follows: Cornea, Aqueous humor, lens and Vitreous body.
1. Cornea: It is the same frontal part of the sclerotic, which is foremost and transparent.
2. Aqueous humor: It is a transparent liquid, which fills up the space between cornea and lens.
3. Lens: It is a body, which is curved at both the ends and is present in the front portion of the eye and behind the iris. It is better that you know that the lens is suspended with the help of suspension ligaments and is joined to the choroid and conceals the surface of the lens with a delicate, transparent and adjustable veil called as crystalloid. The lens is composed of long cord-like cells and some of them even have nucleus. The lens cords are hard and concentrated and they form the nucleus of the lens.
4. Vitreous body: It is a transparent matter, which fills the inner space of the eyeball and is partly condensed in the form of a delicate curtain.
How do we see objects?
From the bodies that are placed before our eyes, rays of light are reflected to our eyes; these rays cross the cornea and enter the lens through the pupil. They pass the lens as well till they are reflected on the Yellow spot at the rear of the eyeball on the surface of retina. In this manner their image, which is reflected and reduced in size falls on sensitive conical cells of the Yellow spot. These cells convey the image through optical nerves to the centre of sight in the brain. The soul or the self of man in this way is able to see objects through this process and reactions and it can become aware of the color, volume and distance of those objects.
Adjustment of image
You know that objects are clearly visible only if their image falls exactly on the Yellow spot, neither behind it nor in front of it. In ordinary circumstances the lens can throws a clear image of anything that is at a distance of six meters or more on the most sensitive part of the eye that is the Yellow spot. But the lesser the distance of the object to eye, the lesser would be its visibility as its image would fall much behind the Yellow spot and hence that object would not be seen clearly.
But according to the plan that is in force in the creation of the eye, this difficulty has been solved in a beautiful manner, in the way that curvature of the lens is changeable. A healthy and normal eye automatically adjusts the curvature of its lens according to the distance of the object whose image it wants to focus on retina. If the distance of the object is lesser than normal the curvature of also increases in accordance with it so that its image falls exactly on the Yellow spot. In such a way: that ciliary muscles exert pressure on the eye and this causes the suspensory ligaments to be elongated as a result of which the surrounding of the lens is stretched and in its middle it is having a hard nucleus, which does not allow the stretching beyond a certain point. In order to see the near objects, the thickness of the lens increases as a result of which the distance of its focus changes and in order to see objects at a distance its thickness decreases. This process is known as focusing. It is one of the most minute and swift action of the eye, which is performed during the seeing of objects. In every moment that we see around us and see the near and far scenes and things, our lens changes its thickness hundreds of times in succession and we see all the objects nicely and clearly. Have you so far paid attention to these minute actions of the eye?
A discourse on Knowing God
We know that this small body is composed of hundreds of smaller organs and millions of different types of cells and each of them have a special function and they perform these functions. Apparently the eye is a small body, but in fact it is a great workshop, which accurately and regularly functions as a camera. It is a collection, which is compatible, aimed and connected and which follows a single aim and fulfills an important need of man; that is to see objects. Truly, if there had been no sight, how dark this world would have been for us?!
Now we pose the following questions to our intellect and listen to its replies: Did the three layers of the eye appear on their own or it is someone else who had created them with foresight?
Did the transparent covering of the eye became transparent by chance or it is someone else who made them transparent so that light may pass through it?
How did the eye come to have transparent aqueous humor and vitreous body? Who has constructed these two liquids with special viscosity and formula? Were the glands that secrete these liquids aware of the needs of the eye? Did the pupil come into being automatically or it was the man who knew that the eye needed an aperture so that light may pass through it, and so he created it in this way? Has the pupil itself selected the required diameter through foresight or it is someone else who has designed and created it in this way? Does the pupil know that it needs to be opened and shut to regulate the passage of light through it? Or it is someone else who informed it of this need and who created it in this way? Did the Yellow spot come to be located in line with the pupil and focus of the lens so that image may form on it or it is someone else who has placed it there?
Did the most sensitive cells of retina come to be situated exactly at the Yellow spot in line with lens or it is someone else who has placed them in this way? Do the optical nerves connect to the cells of yellow spot by chance so that their messages may be transferred to the brain or it is someone else who has preplanned this? Do the optical nerves connect the eye to the brain in aimless way by chance or they have an aim and a creator with aim who has done this?
Who has created the optical lens with such precision and which expert physicist has planned it?
Is the eye also aware of the science of physics and the discussion of lenses? Is the lens aware of its sensitive position? Is the covering of the lens automatically adjustable? Has the eye itself made the act of focusing possible for the lens or it is someone else who has determined this? And whether…?
Lastly, has this systematic, compatible and aimed device come into existence through chance and coincidence or it is a wise and a powerful creator who has created it? The reply is clear to all those who have sense: Study of intricate and diminutive machinery of our eye guides to its wise and powerful creator and in this intricate machinery, we ourselves see the signs of His knowledge and unending power.
Secondary organs of the machinery of sight
Here we shall learn about the first of the secondary organs of the machinery of sight – without which the process of seeing remains defective. We would become familiar with it and after that through posing of questions we will seek to know who their creator is.
As mentioned before the machinery of sight consists of two parts: 1. The eyeball, which performs the function of seeing 2. Secondary organs, which are responsible for protecting the eye and ensuring its movement and hygiene. These organs are as follows: Eye socket, eyelids, tear glands, muscles surrounding the eyes and nerves. We shall explain each of them briefly to know about their functions:
1. Eye socket: It is a bony hollow in the shape of a pyramid whose base is in the front and its tip is at the back. Eye socket is divided into two parts with a concave curtain: the front portion of which is the abode of the eyeball and the rear portion contains the optical nerves, muscles surrounding the eyeball, sensitive nerves and nerves of movement and blood veins; and the space between them is filled with fat tissue.
2. Eyebrows: Which are situated at the frontal portion of the eye socket and they prevent sweat from entering the eyes.
3. Eyelids: They are shaped as parts of skin which are stretched over the eyeball. Every eyelid has skin in its front surface portion and in its rear portion, muscles and tissues are attached to it. The inner surface of the eyelid is covered with a transparent tissue named conjunctiva. Muscles of the eyelid are of two types: 1. Muscles, which contract opening the eyelids 2. Circular muscles, which are pulled over the eyeball.
The function of the eyelids is to protect the eyeball and to prevent entry of foreign objects into it, especially during sleep when there is no need of the function of the eye; it covers its whole surface and protects it from possible dangers. Moreover, in the inner edge of the eyelids, holes are arranged and these (25 or 26 holes) secrete a special type of fat to soften the eyeball. The upper eyelid through systematic and swift movement coveys tears to every part of the eyeball and keep it moist and also does not allow any dust or dirt to accumulate in it.
4. Eyelashes: Which are is the form of some short strands of hair which grow from the edge of the eyelids.
5. Tear glands: Glands situated in the external upper portion of every eye are named as tear glands. These glands produce tears, which are composed of water and a little quantity of salt. Tears secreted from these glands keep the surface around the eyelids covering the eye always moist, and they wash it; the remaining tears collect in the inner corner of the eye and from there are sent to the nose through the tear duct where they gradually evaporate moistening the air which is inhaled.
6. Muscles surrounding the eye: These muscles of the eyeball cause it to move in different directions as follows:
A) Directly outward, which takes the eyeball outward. B) Directly inward, which takes the eyeball inward and towards the nose. Contraction of directly outward muscles of each eye usually moves along with the muscles of the other eye as a result of which both eyes move to the right or the left in unison.
C) Directly upward muscles, which move the eyeball to the top. D) Directly downward muscles, which move the eyeball down etc.
7. Nerves: These include the optical nerves, which receive optical messages from retina and transfer it to the center of brain in form of electrical impulses and other nerves.
A discourse on Knowing God
Now we pose the following questions to ourselves: Is the eye aware of its importance and intricacy of its own existence that chose this solid eye socket as its abode? Or it was by chance that it came to occupy this safe place? Or it was someone else who provided this safe refuge to it as a result of foresight?
Did the eye itself brought into existence eyebrows above itself in order to prevent the entry of sweat? Or the eyebrow was aware of this need of the eye and it hastened to offer this help? Or it was someone else who created eyebrows above the eye?
Did the eyelids by chance become as such in order to protect and wash the eyes? Were the eyelids aware of the hygiene required by the eye that they rubbed fat over its surface and washed it through tears and continuous swift movement? Or it was a wise and a powerful creator who determined this?
Were the tear glands placed in the eye by chance? Who has devised the composition of this disinfectant liquid? Did the tear glands know that salty water is necessary to disinfect the surface of the eye? Is the hole in the corner of the eye – through which the excess tears are drained – come into existence by chance? Or it was the eye which procured this aperture? Was the eye aware of the need of the nose and the respiratory organs to moisten the inhaled air that it causes the excess tears to drain into the nose? Or it was a wise and a powerful creator who designed all this through foresight?
Do the holes that secrete fat in the eyelids come into being on their own? Or the eye, since it needed them, created them? Were the eyelids aware what help they are rendering to maintain the hygiene of the eye by secreting this fat?
Did the muscles of the eye and eyelids with those variations come into being of their own? Or did the eye bring them into existence? Or it was someone else who determined them on the basis of foresight?
Did the optical nerves with all their intricacy and specialty, connect the eye to the center of sight inside the brain automatically? Or it is a knowing being who has determined this connection?
In other words: Is such compatible and systematic collection, all parts of which are connected to each other and pursue and realize a single aim – that is to see – is it possible that it come into being on its own?
Yes, every intelligent person will reply that in such a compatible, interconnected and systematic collection – in whose make-up hundreds of laws and thousands of miniaturizations and amazements have come into action – it cannot be thought to have come into existence by chance or coincidence; it is the wise and a powerful creator who has brought them into existence.
This is the correct reply. When we look at the complex structure of the eyeball and when we study and contemplate on the connection of the eye to its secondary parts and the connection of all of them to the brain and the relationship of this collection with other parts of the body and the connection of the whole body to the outer world, we realize the whole world to be a single and great connection and witness that this great world is having a single, wise and powerful creator, who has created it and who also controls it.
If we look closely and with insight; we would be able to see the signs of the power, knowledge and wisdom of the great creator of the world everywhere. We shall recognize Him and connect ourselves to him with sincerity. And we would humble ourselves in front of His power and greatness and we would thank for the innumerable bounties and blessings from the depths of our hearts. His pure love would permeate throughout our selves. We would realize that only He is worthy of worship and we would accept only His commands and we would submit only to Him.