If you look at the space you are in, you can find familiar objects that you face every day. Even bright colors on various objects seem to be something ordinary for us. As it known, our eyes alone are unable to form the whole picture of the surrounding reality, and vision is a much more subtle and complex function. First, the smallest light particles (photons), reflected from the objects, hit retinas of our eyes. After that about 126 million photosensitive retina cells send the reaction information to the brain for processing. There, the information is almost instantly processed, depending on the direction of refraction and the energy of the photons detected. In the brain, all this is composed into a whole picture containing a variety of shapes and shades.
Where does the edge of the human eye vision lie?
It is quite evident that our vision has limits. For instance, our eye is unable to detect radio waves or see small bacterium. It is possible only for special devices. And here is the question, that can trouble you. How to define a boundary where natural vision becomes powerless? It is possible to answer the question with the help of scientific achievements in biology and physics. Scientists believe that any visible object has a certain visual limit. Under certain conditions, our eyes cease to perceive familiar objects.
The simplest example of experiencing the limit of human vision is the ability to distinguish colors. Colors and shades, which lie within the visible spectrum, for example, purple and amaranth, are distinguished by the wavelength of the light entering the retina. The light-sensitive cells inside the eye, which are divided into two types: rods and cones, are directly involved in this process.
If the first cell type is responsible for the perception of color during the daytime, the second allows us to distinguish light grey shades at night or under dim light conditions. Both cell types contain receptors. They absorb energy and send signals to the brain via our ophtalmic nerves. After that, the complete picture is formed, and we easily distinguish purple from amaranth.
Is it possible to expand the horizon of a human eye possibilities?
Sometimes people can push the boundaries beyond “the allowed” limit and catch the reflection of ultraviolet spectrum photons. It becomes possible due to the absence of eye lens in pathologies or after undergoing a surgery. If the outer elements of a normal eye act as ultraviolet blockers (as this spectrum is harmful to humans, to verify this, try looking at the sun with a naked eye), people with such visual defect can have an expanded range of lightwave perception to 300 nanometers. It is rather interesting to note that ultraviolet radiation, in this case, is transformed into the light of white and blue visible ranges.
Recent research proves that in some ways we can visually capture infrared radiation as well. However, certain conditions need to be observed: two infrared photons must hit simultaneously the same retina cell of the eye. Scientists have found that in this case the energy of photons is summed up and falls within the visible range.
Is it harmful to read at night?
If you have ever read at night or looked at the screen of your mobile phone, especially when a child, your parents might warn you that it was rather bad for your sight. There is another widespread myth concerning children at school. There exists an opinion, that it is very easy to tell a smart child at school from the others. The person is allegedly distinguishable because he or she wears glasses. Wearing glasses implies that a child spends a lot of time at nights reading books and learning something new.
The BBC published an article that is going to debunk the myth about reading under a dim light being harmful. Myopia is one of the most widespread illnesses among people who have problems with eyes. It makes those people unable to see objects at a distance, whether it is a number of the bus or a road sign. Using glasses can solve this problem partially. However, there is no explanation why some people suffer from it, and others don’t. And one more important question is why it develops at the young age in some kids when others don’t have such a problem.
A scientific explanation of vision problems
Our eyes evolved to adjust to different levels of light. If you are trying to read in the darkness, your pupils are becoming larger. It happens so because eyes are trying to capture more light through the lens on the retinas. After the collected light energy transformation, the information collected by the cons and rods is passed further to human brain. You get the image and understanding of what you see now. Your eyes are adjusting to the light level. But sometimes people are complaining that this accommodation causes a headache and a pain in their eyes.
If you are in the darkroom, and then the light turns on, your eyes are adjusting to a new lighting level. It gives you the ability to see both in the daytime and at night. British scientists claim that the way of life can influence the development of myopia, but it is not a leading factor. It can be the result of hard work at a PC desk, but it almost has nothing to do with such factors as a child’s weight at birth or the way of life the mother have been leading during her pregnancy.
10 interesting facts about human eyes
- The size is important. A diameter of a human eyeball is approximately 24 mm, but it can vary because of some conditions.
- Eyes color. All the children are born with grey-blue eyes. And only two years after their eyes obtain their real color.
- Darkness and light. The human ability to see during the day and night deals with different types of retinal photoreceptors.
- Upside down. An object image, projected on the retina, is turned upside down. But our brain flips the image to a normal position, so we see the world and objects in a normal state. It works like a lens in a camera.
- Color blindness. This heritable disease was first described by John Dalton, who had found he was unable to distinguish a red color. It is more widespread among men than women.
- For now, it is impossible to perform full eye transplantation. Even with all the advancements of medical science, it is still impossible now.
- When you sneeze, your eyelids are closing. It is a protective reaction to avoid the rupture of eye capillaries.
- The human sight is half as sharp as that of an eagle. It is so due to the eagle vision system structure and the ability of the lens to change its curvature.
- According to the statistics, more than 300 million people are suffering from problems with vision. And almost 39 million people are blind.
- The constant use of properly selected glasses and contact lenses does not harm the wearer eyes and cannot impair the person’s vision.