The human body is imperfect and fragile. For centuries, we have been trying to cope with several risks, competing and researching diseases, etc. All to extend our life expectancy.
Today, we have many privileges that we have gained through the knowledge accumulated over the centuries through trial and error (sometimes fatal), and we can say that we are entering a new stage of evolution. Namely, the improvement and enhancement of our capabilities.
Today, we will discuss an issue that has long troubled the human mind and imagination. Specifically, the capabilities of human eyes. After all, the inability to see in the dark has cost heroes their lives more than once. This was mainly a severe problem when hunting active animals in the dark. Or even more so during military operations, when stealth was supposed to be the main advantage.
An interesting fact. British pilots did not have modern night fighters during the Second World War to protect themselves from German night raids. But they did have carrots. It was carrots that the UK Ministry of Food cited as the reason for the successful counterattacks by British pilots. Allegedly, thanks to its consumption, they improved their eyesight so much that they could see enemy aircraft well in the dark. The ministry also advised citizens to eat carrots to help them see better during power outages. They were explicitly introduced to make conducting night raids more difficult for the enemy. For these reasons, the authorities began to encourage people to consume more food that could be grown in their gardens. Advertisements such as "Carrots keep you healthy and help you see in the dark" were distributed everywhere. The press even attributed the success of British ace John Cunningham, nicknamed Cat's Eyes, to carrots. He shot down 20 enemy aircraft, 19 of them at night.
However, we all eat this vegetable mostly. But no miracle happens to our eyes. The success of British intelligence officers was due to the use of a secret on-board radar that helped detect enemy aircraft. And the myths about carrots were just a means of distraction. It is difficult to say how successful it was. However, sources claim that this exciting story had its impact.
But are there any vitamins that could help us better navigate in the dark? In general, how the human visual apparatus works. What prospects do we have in the future on this issue? This is what we will try to explore today.
How we see: adaptation
The human eye is a complex mechanism that allows us to see the world around us, perceive colors, see the faces of people close and dear to us, and admire all the colors of our planet. Most of the information that enters the human brain enters through our eyes. The human eye converts an electromagnetic pulse into a visual image (the picture we see).
It has powerful adaptation mechanisms, i.e., adapting to different lighting conditions. The brightest and darkest light signals our eyes perceive differ about a billion times.
So, now let's imagine that the lights in your apartment have been abruptly turned off. Remember how this process works? At first, the eye sees absolutely nothing; then, maybe you start to distinguish some outlines of the surrounding objects. And someone suddenly switches on a flashlight, pointing it at you. What happens at this point? A bright spot of light appears and blinds you so that for a few moments, you see a spot-silhouette of this person in front of your eyes - a so-called sequential visual image. A sequential visual image is a sensation that continues after the stimulus has ceased.
For example, when we look at a lamp, we close our eyes but still see the light for a while. It is caused by a sudden change in light from dark to bright, and your eyes need more time to adapt. As a person walks by and lights up everything around you, your visual system gradually stabilizes. The light reflected from the surface of the objects around you hits the light-sensitive cells in your retina, the rods and cones. These receptors transmit the brain information about colors, shades, and shapes. And only after a few seconds, after the light appears in this exciting process, can you begin to see something more clearly.
The cones themselves are concentrated mainly in the central part of the retina. The retina is the built-in, sensitive membrane of the eye, which is the thinnest membrane and performs the role of image formation (light and color perception). The retina's role can be compared to the film in a camera that captures an image. With their help, we can see colors and shades with high resolution. However, cones are active mainly in bright light, such as during the day. The area where the cones are most concentrated is called the macula. This is where light is best perceived.
Rods are located closer to the periphery. They work in low-light conditions and are more light-sensitive than cones. The rods are responsible for peripheral and night vision; with their help, we see everything in shades of grey. That's why "all cats are grey at night". The place where the optic nerve leaves the retina, without photoreceptors, is called the blind spot. This is where the eye does not perceive light. There are approximately six million cones and 110 million rods on the human eye's retina. This, in turn, tells us that due to the high concentration of cones in the central part of the retina, our color daytime vision is more powerful than our night vision.
Meanwhile, assuming that cones and rods work alternately is a mistake. The former is active only in good light, and the latter is activated only in the absence of light. This is far from the case. They interact organically with each other. Because the brightness of the light changes constantly during the day, sometimes this process is not noticeable. It is automatically tuned in our body, and these two photoreceptors continuously respond to stimuli.
Adaptation of the eye to different lighting conditions is ensured by cones and rods, where the photochemical reaction of pigments (opsins, or "visual pigments") takes place: rhodopsin in rods and iodopsin in cones. The cones (there are three types) have one of three types of opsins with different sensitivities to the light spectrum. This is important for color vision. During the day and at dusk, the photoreceptors are constantly breaking down and rebuilding visual pigments under different light levels. This results in a nerve impulse transmitted through the optic nerve to the visual cortex, where graphical images are formed.
The dark adaptation process (when the eyes get used to the dark) can take an average of 30 to 40 minutes. Sometimes even longer. To adapt from complete darkness to bright light, i.e., the eyes need only 5–10 minutes for light adaptation.
In addition to these reactions, our visual apparatus uses two other mechanisms to adapt to different degrees of light. The first is the reflex reaction of the pupil to the brightness of light provided by the iris muscles. Changes in the intensity of the light flux directed to the retina affect the power of photochemical reactions. Therefore, in the dark, the pupils dilate to perceive more light, and in bright sunlight, on the contrary, they constrict. By the way, a camera works on the same principle. To make a photo more straightforward in low light, you need to increase the diameter of the camera shutter so that more light can penetrate it.
The second mechanism concerns the work of retinal neurons. When the light decreases, signal transmission intensity between retinal neurons is initially low. Still, it increases in a matter of seconds, which can significantly improve night vision. These mechanisms reinforce each other and allow us to adapt to different lighting conditions quickly.
About colors
An interesting observation. During the day, yellow, orange, or red objects seem the brightest, while at night, it is easier to distinguish green shades. This is because cones and rods are sensitive to wavelengths of different lengths. Cones are most susceptible to light in the red and yellow parts of the visible spectrum, while rods are sensitive to blue and green. The Purkinje effect is the phenomenon of changing color perception when the light level decreases. Jan Evangelista Purkinje is a Czech biologist and public figure. His works are mainly devoted to physiology, such as vision, histology, and embryology. He organized the Society of Czech Doctors, fought to create the National Academy of Sciences, etc. He explains why red colors appear darker to us when it gets dark than during the day and almost black at night. At the same time, blue objects appear lighter at dusk and night than during the day.
Despite the change in color perception. If we know that an object has a specific color, it will remain so for us. For us, green grass is always green, and white snow is always white. This allows us to recognize familiar objects and find our way around easily.
Is it possible to improve night vision?
Let's go back to our theory about carrots. It has the same chances of improving our eyesight and ability to see in the dark as excessive blueberry consumption can turn us blue. In other words, it has no chance. The issue is that this root vegetable contains beta-carotene, a pigment that our body uses to produce vitamin A. If this vitamin is deficient, chicken blindness can develop - when a person sees poorly in low light. After all, vitamin A is a part of rhodopsin, a rod photopigment that ensures vision adaptation to the dark. However, taking beta-carotene or vitamin A supplements can only improve the functional state of the retina to a certain extent. And that is if a deficiency of this vitamin causes the disease. After all, chicken blindness can also be hereditary.
Of course, scientists have raised the issue of vitamin A intake to improve the ability to see in the dark. However, excessive consumption can only lead to negative results, mainly because the body regulates the absorption of this compound to prevent its excessive accumulation.
So. We have found that vitamin intake will not help the normal eye see in the dark.
But this question remains relevant. And scientists of various specialties have long been trying to solve this problem.
Less than a century ago, night vision technology was introduced. These devices work by amplifying the available light. Despite all its improvements, the military still uses special equipment that is not always comfortable to use. It is bulky and requires prior familiarization with the equipment, adjustments, etc. Therefore, researchers set out to improve the biological capabilities of the visual apparatus.
Many recent experiments have been conducted to study organisms that can see in the dark.
Let's get back to night vision devices. They work by scanning the environment using infrared light. That is the spectrum that the human eye cannot see. So, the logic is to allow the eye to see this range. To do this, applying a thin layer of nanoparticles to the retina is enough, which makes the photoreceptors respond to infrared radiation outside the visible spectrum.
The technology, developed at the University of Science and Technology of China, has been successfully tested on mice, and there is every reason to believe that it will prove equally effective for the human eye. What did the experiment consist of?
A unique injection with the previously mentioned nanoparticles was injected into the eyes of the mice. After that, they were placed in a Y-shaped tank with water, with one branch they could use to get out. The researchers used visible light to teach the animals how to find a way out. The experiment showed that the mice with the injection could cope with the task because they had already followed a specific route in the dark.
The mice retained the ability to perceive invisible infrared rays for several weeks after the application of the drug, with almost no side effects. However, the only way to "switch on" night vision is to inject nanoparticles directly into the retina. Scientists do not rule out that ordinary eye drops will be enough in the future for this purpose.
Future and relevance.
So. This is the first option for developing events and self-improvement.
What else can we suggest? It's worth mentioning cyber improvement here. Some time ago, the world began to translate the boldest ideas of science fiction writers into our reality. We think it's worth noting that inventing something new in our era is extremely difficult. All further discoveries will be based on improving the existing one or combining separate technologies into one.
If you think about it, prosthetics have existed since people lost a body part and survived. Remember the stories about pirates who had hooks instead of arms? Today, scientists are creating prostheses that a person can control with the help of their nerve endings, which are "felt" by the device. Therefore, it is possible to assume that in just a few years, what has long been described in books and films about the future will become an utterly commonplace reality. A cyber-enhanced eye will not only be able to see the world more clearly and vividly but will also be able to zoom in on objects under observation. Remarkable eyes with night vision will be created for the military.
On the one hand, we understand the privileges that cyber improvements provide. But the main question is whether this is necessary for humanity, which only looks to make its existence easier. This is an advantage for people who, for example, have returned from war. This is an extraordinary discovery that gives such people the opportunity to live a whole life. Or to correct genetic problems. Situations when a person cannot receive information through the visual apparatus from birth.
So, let's summarize the main points. Our visual apparatus can adapt to darkness even without improvements. The interaction of cones and rods helps it do so, where the latter are responsible for distinguishing objects in the dark. We cannot see as clearly in total darkness as we do in the daytime because our eyes cannot cover the infrared range. And it is precisely this issue that scientists are addressing. They have set out to create a particular protein molecule with nanoparticles that will make photoreceptors respond to infrared radiation outside the visible spectrum.
The solution to this issue is the basis of the experiment to improve the ability to see clearly in the dark without using additional devices.