The study of Physics Topics can help us understand and solve real-world problems, from climate change to medical imaging technology.
Why Do We Have Two Eyes For Vision And Not Just One
There are many advantages of having two eyes instead of one. Some of these are given below.
1. Having Two Eyes Gives a Wider Field of View. A human being has a horizontal field of view of about 150° with one eye open but with two eyes open, the field of view becomes 180°. Thus, having two eyes gives a wider field of view. This means that with two eyes open, we can see a much larger area in front of us (than can be seen with only one eye).
The human beings have two eyes at the front of their head, so their field of view is limited to about 180° (see Figure). Some animals, however, have their two eyes located on the opposite sides of their head. Those animals who have two eyes on the opposite sides of their head have the widest possible field of view. They can see much larger area around them than the human being can see.
The animals of prey (like rabbit, deer, chicken, fish, etc.) have their two eyes on the opposite sides of their heads so that they can see their enemies (predators) in a very large area around them and try to escape from them (see Figure). A domestic animal having its two eyes on the opposite sides of the head is horse.
2. Having Two Eyes Enables Us to Judge Distances More Accurately. Our two eyes are a few centimetres apart from each Figure. Rabbits are animals of prey. They other (see Figure).
Due to this, the two eyes see the same object have Two eyes on the sides of their head, from two slightly different angles and send two slightly different images of the same object to the brain. The brain combines these two slightly different images to build a three-dimensional picture of the object which enables us to judge the distance of the object more accurately.
This will become clear from the following example. Let us take two sharpened pencils, one in each hand. Stretch the arms forward and try touching the tips of pencils first with one eye open and then with both eyes open. We will find that it is difficult to touch the tips of two pencils with one eye open but it is much more easy when both the eyes are open (see Figure ).
This is because with both the eyes open, we can judge the distances of the pencil tips more accurately. Human beings (and all other animals having their eyes at the front of their head) are said to have stereoscopic vision (or stereopsis) which gives the perception of depth. All the predators (like tiger, lion, etc.) have their eyes at the front of head so that they can judge the distance of their prey accurately and catch them easily (see Figure).
The Gift of Vision
There are millions of blind people in our country who cannot see at all. The eyesight of most of these blind people can be restored if they are given the eyes donated by other persons after their death. In this way, our eyes can live even after our death. In fact, our two eyes can give eyesight to two blind persons (each getting one eye), and make them see this beautiful world.
Some of the important points to be noted about the donation of eyes are the following:
1. Any person of any age or sex (male or female) can donate eyes. People who wear spectacles or have undergone cataract operations can also donate eyes. Even the persons having ailments such as diabetes (sugar), hypertension (blood pressure) and asthma can donate eyes.
But they should not have any communicable diseases. The persons who were infected with or died because of diseases such as AIDS, hepatitis B or C, rabies, leukaemia, tetanus, cholera, meningitis, or encephalitis, however, cannot donate eyes.
2. After the death of the person (who had registered for eye donation), the eye bank should be informed immediately. This is because eyes must be removed within 4 to 6 hours of a person’s death.
3. The doctors of the eye bank team will remove the eyes at the home of the dead person or at the hospital. It takes only 10 to 15 minutes to remove the eyes. There is no disfigurement of the face in this process.
4. The eye bank distributes the donated eyes to various eye hospitals where these are transplanted in the blind people through surgical operation.
5. Those donated eyes which are not suitable for transplantation, are used for doing research and for teaching purposes in medical colleges.
We can, even today, make a pledge in writing, with the eye bank of our area that (God forbid) whenever we die our eyes should be removed and given to the blind persons to light up their dark world !
We should be grateful to God that he has given us the gift of vision to see this wonderful world. Let us pass on this priceless gift of vision to our less fortunate blind brothers and sisters by registering our name for eye donation.