For most living things, good vision is a key factor for survival.
How then do animals whose eyesight is not the best and who have the worst eyesight in the world survive?
If, for example, a wild predator cannot see its prey, it will die of starvation, and harmless herbivores themselves will become victims. But there are creatures in the world who can easily get by with minimal abilities to see the world.
The mole is rightfully considered a leader in blindness.
No wonder they say: “blind as a mole” or “mole’s vision”, that is, practically none. However, the mole is not completely blind, and he has some abilities for visual perception of the world.
Who has the best eyesight in the world? Read about this in this article .
How the most visually impaired eyes in the world work
The eyeballs of this animal do not exceed two millimeters. Despite the fact that their retinal structure is the same as that of other mammals, they lack the cones and rods necessary to distinguish colors and contours.
Almost all photoreceptors in a mole's eyes have the same shape, and they are concentrated mainly in the very center of the eyeball. Along its periphery they are mostly atrophied.
The fact is that the mole spends most of its life underground, and it is always dark there, regardless of the season or time of day. It turns out that the mole does not need keen eyes, because it finds food by touch and smell with the help of a hypersensitive nose.
But large eyes, given his lifestyle, would greatly disturb the mole and would even pose a danger. With constant digging of the earth, its particles would fall into them, which would cause injuries and suppuration, and then death.
It is also important that when smell dominates over the other four senses, this ability uses a large part of the brain. Devoting too many gray cells to vision at the expense of smell and other important senses would be extremely irrational. However, the mole still needs eyes, so they will never disappear completely.
Causes of blindness
The fear of going blind very often prompts suspicious people, when going to doctors, to ask rather stupid questions, for example: can people go blind in their sleep? At the same time, it will not be difficult for any competent specialist to explain that in absolutely healthy people, sudden blindness does not occur. This pathology can result from conditions and diseases such as:
- Diabetic retinopathy.
- Glaucoma.
- Cataract.
- Degeneration of the optic spot.
- Trachoma.
- Onchocerciasis.
- Keratomalacia ixerophthalmia.
- Head or eye injuries.
There are a number of specific types of blindness:
Colorblindness. This is an anomaly in which a person cannot distinguish colors that others can easily distinguish. Pathology, as a rule, is genetically determined and transmitted through the male line. According to statistics, it is detected in almost 8% of men; in women, this figure is less than 1%. Moreover, in such patients, in most cases, visual acuity remains normal.
Night blindness. With this pathology, a person loses the ability to distinguish surrounding objects at dusk. Such a disorder can be of a genetic nature or develop as a result of a number of diseases. The overwhelming majority of patients with night blindness have normal visual acuity during daylight hours. Therefore, it is quite difficult to call such a phenomenon blindness.
Snow blindness. This is a deterioration or complete absence of visual perception due to the powerful impact of UV rays on vision. Most often, such a violation occurs over time due to the proliferation of tissue on the surface of the cornea. Snow loss of vision is temporary and never results in complete blindness. The movement of objects, bright light, the outlines of objects, people see in any case.
Blindness, as a vision pathology, can be temporary or permanent. In order to determine the degree of impairment, the visual field is measured, as well as the acuity of perception, separately for each eye. The ability to see can sometimes disappear suddenly, or deteriorate slowly (when the cause is a disease), gradually being completely lost. In any case, to determine the degree of blindness, you must visit an ophthalmologist. It must be remembered that some types of even complete blindness are reversible. However, when a patient is diagnosed with dysfunction of the optic nerve, as well as in the event of a cerebral hemorrhage, it is almost impossible to restore vision.
So what does the mole see?
Tiny mole eyes distinguish between light and darkness so that the animal understands where it is, underground or on the surface, and distinguishes day from night.
In addition, a mole can distinguish a moonlit night from a cloudy one. It is thanks to vision that a mole can make passages under the snow, swim across rivers and streams, and even hunt underwater. These actions with such a weak ability to see seem overly complex, but the mole carries them out, attracting other senses, which greatly facilitates the tasks.
A mole can distinguish contrasting colors; for example, it can easily distinguish red from green and yellow. The animal does not see the outlines of objects, but determines their approximate dimensions by changes in illumination.
By the same principle, moles recognize moving objects, although they, of course, seem to them to be nothing more than a blurry spot. Because they do not understand who they see in front of them, a hunting predator or just a passer-by, moles are so difficult to see on the ground - they hide at the first sign of the appearance of other living creatures.
It is easy to understand what a mole sees and how the poorest vision in the world works. To do this, you need to put a dark cloth bandage over your eyes. Shadows and light sources will be visible through it, and it will be clear what size the object is moving in a certain direction. But it will be impossible to identify familiar objects.
However, you should not think that moles have a poor understanding of what comes their way. As already mentioned, these small garden pests recognize other animals and food by smell. So moles are unlikely to experience any difficulties in life.
Geography of an ophthalmologist: which countries have the poorest vision?
Blurred vision is a modern problem, and every year ophthalmologists around the world have more and more work to do.
According to WHO, various eye diseases affect 1.3 billion people on the planet. If the situation does not change, according to scientists, by 2050 half the world's population will be myopic. But this does not mean that it is time to declare war on computers and smartphones. It turns out that not only high technology is to blame for the deterioration of vision.
Residents of which country are most often concerned about eye diseases and why?
Most people with visual impairments, as well as blind people, live in South, East and Southeast Asia. Is it possible to say that computerization in these countries has advanced further than, for example, in the USA? Hardly. Meanwhile, in America and Germany, only 10% of primary school students are myopic, while in China this figure reaches 40%.
Among other possible reasons, ophthalmologists cite features of eye physiology, hormones and genetics in Asians. They also talk about social factors: they blame the shortcomings of the education system and even the specifics of writing. After all, reading intricate hieroglyphs requires much more effort from the eye muscles than simple Cyrillic and Latin letters.
In addition, the home lifestyle of Asian children also contributes. While in Australia the average schoolchild spends 3–4 hours a day outside, in China it is only an hour. Sunlight promotes proper biochemical processes in the retina, as a result of which the elongation of the eyeball slows down (the main cause of myopia). If there is not enough sunlight, vision decreases. Beijing doctor Tongren Guo Ying considers high income to be the root of evil: in prosperous families, gadgets and a thirst for knowledge appear more often. It’s hard to argue with this, but at the same time there is a reverse trend. In rural areas and poor areas, people do not have enough money or knowledge to buy good glasses.
Is myopia related to standard of living?
Be that as it may, global statistics refutes the assumption that myopia and blindness are diseases of rich countries.
The study found that vision problems are least likely to occur in people over 50 in Western Europe, Australia and parts of the high-income Asia-Pacific region. The situation with vision in middle and old age is worst in Afghanistan, Ethiopia, Yemen, Chad, Cameroon and Niger. There, more than 7% of people over 50 have blindness.
Obviously, official statistics do not reflect the full picture. Medicine is not equally accessible everywhere. Not every resident of a thatched hut has a leak-proof roof, let alone a clinic at least an hour's walk away. In some places, there is simply no one to turn diseases into dry statistics. In addition, myopia in third world countries may go unnoticed during more urgent tasks such as fighting numerous infections and parasites. And over the years, a “harmless” visual defect, left unattended, can develop all sorts of complications, including blindness.
What is being done to reduce the incidence?
In developed countries, things are not so bad, but the level of awareness about eye diseases also leaves much to be desired. Therefore, 12 years ago, the French company Essilor founded a charitable foundation so that as many people as possible could see the world clearly. The Vision For Life program operates in the USA, Southeast Asia, China, India, Australia, New Zealand, Canada and other countries. In Russia, active educational and charitable activities are also in full swing.
Vladimir Zolotarev, ophthalmologist and head of Essilor Academy Russia:
“In 2021, we launched the Crizal Healthy Vision Program. A clear view of the world": we give glasses with high-quality lenses to children from large and low-income families, and raise awareness among the population about the need for regular eye exams. The last point is especially important. Experts suggest that within 10 years, visual impairment will be observed in 70% of the Russian population. These sad forecasts concern us and our children. Therefore, we never tire of telling everyone about how important it is to maintain visual hygiene, regularly visit an ophthalmologist and be sure to correct myopia, farsightedness and other types of visual impairment. I hope that in Russia and in the world the level of awareness about eye health will increase, and the incidence of vision diseases will decrease!”
About company
Crizal is an innovative brand of eyeglass lenses from the international company Essilor, which has been producing high-quality lenses and optical equipment for over 160 years. The company was created in 1972 as a result of the merger of two of the largest French eyewear manufacturers: the Essel Society of Eyewear Makers, founded in 1849, and the Silor company, created in 1931 by optician Georges Lissac. Essilor holds more than 5,700 patents in the field of spectacle optics and special equipment, and annually invests 200 million euros in research.
Who doesn't need vision?
Mole rat
There is also an animal that, having eyes, does not see at all.
This is a mole rat - another animal that lives underground.
His eyes are completely atrophied and hidden under folds of skin, which with great stretch can be called eyelids. The giant mole rat, the largest rodent in its family, has completely lost its eyes as a result of natural selection. It is unlikely that this gray underground inhabitant can be the leader in the poorest eyesight due to the lack of it.
What causes visual impairment?
With myopia, the rays that are reflected from surrounding objects are focused not on the retina itself, but in front of it. In this case, important roles belong to both the structure of the cornea and lens, and the increase in the anterior-posterior axis of the eyeball. The image projected on the retina becomes blurry.
Minus lenses are used to correct myopia. Their strength depends on the severity of the refractive error:
- Weak (with deviation – 3 diopters);
- Average (with refractive error from -3 to -6 diopters);
- High (with a deviation of more than -6 diopters).
At the same time, myopia is not always the only ophthalmological problem; often a patient with myopia develops so-called presbyopia with age. This combination of diseases requires the selection of special glasses (multifocal, bifocal).
Myopia is often combined with astigmatism. In this case, the help of an experienced ophthalmologist is required to restore the patient’s vision.
