In other eyes: how does human vision change?

In other eyes: how does human vision change?

The world is changing rapidly. Modern man spends more and more time indoors at computers, absorbing and processing huge flows of information. It is completely impossible without good vision. Much depends on him: the success of the child at school, labor productivity, professional fitness and even road safety. The importance of a complete vision is hard to overestimate. In this small review I tried to figure out how well the inhabitants of our planet see and what will change in the near future.

What is considered bad vision?

The criteria for determining blindness and low vision are different in different countries. In Russia and the UK, they are similar. Blindness is visual acuity of 0.02 or less.

In this case, a person can right

count the verifier’s fingers from a distance of no more than one meter. Visual acuity from 0.02 to 0.2-0.3 is considered low vision. If glasses or contact lenses increase visual acuity, then the best result is taken into account. According to The Lancet Global Health, today in the world there are about 36 million blind people and 217 million visually impaired. In the near future, the world’s population will increase. In connection with the increase in life expectancy, the number of elderly people will increase. Therefore, by 2050, a threefold increase in these indicators is expected. About 115 million blind and 218 million visually impaired will need the support of others.

eye diseases at Africa and Asia

According to WHO statistics, 90% of the visually impaired live in developing countries. The cause of blindness is most often cataract (65% of cases). In 17% glaucoma is to blame. Less commonly, trachoma, onchocerciasis, and keratomalacia caused by malnutrition lead to blindness. Trachomais a dangerous infectious disease that is common in the tropics and subtropics. It is characterized by acute inflammation of the conjunctiva, followed by scarring. A frequent outcome is corneal opacification, which causes irreversible blindness. Early treatment leads to full recovery. Thanks to vigorous measures, the incidence of trachoma by the beginning of 2000 was reduced by almost 4 times. Onchocerciasis is common in central and western Africa. This disease is also called river blindness, because its vectors live along the river banks. The causative agent of the disease is a helminth. Through the midge carriers, the parasite larvae enter the body. Here they grow up and begin to give offspring. The main harm to a person is caused by the larvae ─ microfillaria . They affect the skin, eyes and lymph nodes of the diseased. Under the skin, the larvae form nodes up to 7 cm in diameter. With the flow of blood, microfillaria enters the eye. Here, the larvae can cause sluggish inflammation, retinal detachment, or massive intraocular hemorrhage. All of these conditions lead to blindness. Against the background of malnutrition and vitamin A deficiency, children can develop keratomatization . These are severe changes in the cornea, which are manifested first by its drying and then by softening and perforation. It heals with the formation of a rough eyesore. So, the leading cause of blindness in developing countries is a cataract, which is successfully treated surgically. Onchocerciasis, trachoma and avitaminosis are also not a problem for modern medicine. In about 80% of cases, blindness in these regions can be cured or prevented from developing. Such sad statistics is due only to the level of development of the economy and health care in developing countries.

How does the civilized world see?

The leading causes of blindness in Western Europe and America are diseases of the posterior segment of the eye. Most often it is age-related macular degeneration. So, ophthalmologists call the central zone of the retina, which provides clear vision. Blindness occurs a little less often due to glaucoma and diabetic retinopathy. In fourth place are injured eyes. Cataracts are common. But it is usually cured surgically and does not lead to blindness. In Russia, the situation is similar. The main cause of visual disability is glaucoma. It is followed by eye injuries; third place steadily belongs to myopia (myopia) of a high degree. In the latter case, the cause of weakness is not the disease itself, but its complications. The fact is that with myopia there is an increase in the eyeball in the anterior- posterior direction. At the same time, the retina is strongly over- stretched. In it form heavy structural changes. This significantly reduces visual acuity and often leads to retinal detachment. Myopia ─ «norm” of the future? Currently, the unprecedented growth of myopia is a worrying trend in all developed countries. For example, a study by King’s College in London found that 25% of people in the European Union are short-sighted, half of whom are young people under 30 years old. Commentary by expert Katie Williams (Katy Whiliams), Specialist, Department of Ophthalmology, King’s College We are seeing an increase in the number of myopic in many regions. In the big cities of Southeast Asia, 8 out of 10 young people do not see well. Europeans have long believed that this will not affect them. However, now we are seeing an increase in myopia in Europe. Forecasts for the future are also not encouraging. The journal Ophthalmologypublished the results of a study according to which a sevenfold increase in myopia is expected from 2000 to 2050. By the end of this term, about half of the inhabitants of our planet will become myopic. If treatment methods remain up to date, then every fifth of them will have a high risk of blindness due to complications of myopia. By 2050, it will become the leading cause of blindness in the world.

Why does humanity’s eyesight deteriorate?

There are different versions of what is happening. However, most scientists from different countries see the reason for the abrupt change in living conditions. An interesting study conducted over half a century ago. The visual acuity of the Eskimos living in northern Canada was estimated. In the older generation, myopia was almost not observed. But 10-25% of children were already short-sighted and needed glasses. Why did this happen? After all, the parents were completely healthy! Here is clearly manifested the action of the environment. It was at this time that the Eskimos began to move from hunting and fishing to a Western way of life. It is associated with learning and a long stay indoors. This affected the growth of myopia. Interestingly, in Russia, the number of people with disabilities because of high myopia is twice as high among city dwellers than among villagers. Scientists suggest that the most important factor influencing the formation of myopia is lack of sunlight. But genetics, a sedentary lifestyle, long-term fixation of the eyes at close distances play a not so significant role in the development of myopia. This version is confirmed by a study conducted in Australia. A group of schoolchildren was given a special watch for 2 weeks. Every 30 seconds they noted the child’s physical activity and the level of illumination around him. Conclusions were unambiguous. Children with myopia also moved a lot, like their peers. However, they were much less in the bright sunlight outside the room. This was probably the decisive factor that led to the development of myopia. In general, the formation of myopia is influenced by a complex of factors, the leading one of which is the lack of staying in open space in bright natural light.Therefore, to preserve the vision of foreign scientists recommend to be in the fresh air for at least two hours a day. 

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