Sixty years ago, about 20 per cent of the Chinese population suffered from myopia (short-sightedness) but nowadays the figure is more like 80 per cent. In the USA, 42 per cent suffer from myopia, compared with 26 per cent 30 years ago. In southern Europe, about 35 per cent of people are myopic, while in the north it affects one in every two people. In Spain at present, about 25 to 30 per cent of the population has myopia.
With figures like these it is no surprise that myopia is now considered a new pandemic, because in recent years there has been an alarming increase in different parts of the world. Why is this? Is it because people nowadays spend so much time looking at computers and mobile phones?
Dr Sara Bueno, professor of optics and optometry at the CEU San Pablo university and a member of the academic committee of the Visión y Vida association, says various factors are involved. Some are well known, and others less so, and it is possible that some have yet to be determined. There are genetic factors - as many as 24 genes have already been identified whose carriers have a greater risk of developing myopia - and environmental factors can also play a part.
The studies into environmental factors which are associated with the onset and progression of myopia have analysed lifestyles, schooling and the number of hours of exposure to the sun. Children who spend a lot of time at home or in enclosed places, studying, carrying out tasks or playing on the computer are much more likely to show signs of myopia. “But it isn’t because of the screen as such, it’s to do with the surroundings, the distance and the extra effort it involves for the visual system. The type of light is also important, because it is artificial light and not sunlight,” explains Dr Bueno. It seems that the less time that children spend in the fresh air, the higher the risk of myopia and other vision problems.
Dr Bueno recommends spending around three hours a day outside in the fresh air, as a means of prevention. “What we can say is that less use of technology and more walks or playtime outside can help prevent vision problems,” she explains.
Myopia is a defect in refraction which is usually detected when children are at school. Because they cannot see at a distance, they hold their book close or need to be near the screen they are looking at. They may squint when they look at things, or are unable to read what is written on the blackboard very well. These are obvious signs and can easily be spotted by parents and teachers.
However, a study called ‘The visual health of children in Spain’, which was presented by the Ministry of Health in November last year, shows that 60 per cent of parents of children who wear glasses said that it was their child who realised that they couldn’t see very well. And not all sight problems are myopia.
“Other common problems that we find are alterations called non-strabismic binocular disorders, in which the eyes are not able to work together very precisely. That means that the child has to make extra effort to see properly,” says Dr Bueno. This effort causes fatigue and lowers performance in school work, which can lead to failure. These children often put their head on one side to read, or close one eye; it is hard for them to understand what they are reading, they sit in unusual positions while doing their homework... when an optometrist detects these problems they can correct the errors in graduation and usually give the child a series of eye exercises to do so they learn to work together.
“Sometimes there can be other refractive problems such as hypermetropia, or long-sightedness, which, contrary to myopia, doesn’t make the child feel that he or she isn’t seeing properly. They are able to make an effort with their eyes which enables them to see well, but this extra effort causes headaches, visual fatigue (reading or doing close-up work makes them tired), their performance at school suffers and their eyes water,” says Dr Bueno. Correcting the eyesight helps to relax the system, because spectacles mean that the eyes don’t have to make so much effort.
In addition to these, other problems can also affect performance such as strabismus (crossed eyes) amblyopia (lazy eye), or changes to ocular motricity. “The children are not able to follow objects with their gaze. It is difficult for them to read because they can’t follow the line or they use a finger to indicate where they are on the page. This can affect their reading and learning,” she explans.
When these conditions are detected and diagnosed the optician or optometrist will correct the vision, either with glasses, contact lenses or through different therapies and visual training which help the children to perform normally at school. As shown above, every sight problem ‘emits’ different signals.
But beyond affecting children’s studies, does poor eyesight affect them in other ways? “Yes; if myopia, problems with spatial vision or strabismus are not corrected they can affect the child’s leisure activities and also sports where they need good distance vision or precision, such as judging the way a ball is moving,” says Dr Bueno.
Unable to see in 3D
The new technologies can also reveal possible vision problems which have not been detected before. For example, 15 per cent of people are unable to see in 3D. Until this type of film came on the scene, many of these problems would not have been noticed. Now, professionals warn that people who feel dizzy or tired when they watch 3D films could have problems with their vision.
“When we look at something, each eye forms an image in the retina and projects it to the brain. When the brain collects the information which comes from each eye, these different images give us a feeling of tridimensionality or depth. If there is a problem with the sight in one of the eyes or differences in graduation between them, or some of the binocular problems mentioned earlier which mean that the eyes have difficulty in working together, those people cannot transform the image they receive in each eye into a tridimensional one. Or they do, but it takes a lot of effort, and they often get a headache or even feel sick when they watch 3D films,” says the doctor.
Important changes in the development of the eye and visual function occur throughout childhood, so regular eye check-ups are essential. Symptoms are detected in about 20 per cent of children, and those who were born prematurely, or in cases of difficult birth or parents with hereditary visual problems, should be carefully monitored to prevent problems in the future.