Myopia is at epidemic level and the problem starts in childhood

The Conversation, by Andrew Herbert

New York: Myopia, or the need to correct vision to focus or see distant objects, has become very common in recent decades. Some people believe that nearsightedness, also known as myopia, is an epidemic.

Optometry researchers estimate that if current rates continue, about half of the world's population will need corrective lenses to offset myopia by 2050, up from 23% in 2000. %, and in some countries it is less than 10%.

The associated medical costs are enormous. In the United States alone, spending on corrective lenses, vision tests, and related costs can amount to $7.2 billion annually.

Why is there a rapid increase in myopia?

I'm a vision scientist who studies visual perception and perceptual deficiencies. To answer this question, let's first look at the causes of myopia and what can reduce it.

How myopia progresses

Having two parents with myopia increases the chance of developing myopia, but there is no single myopia gene. This means that the cause of myopia is behavioral rather than genetic.

Optometrists have learned a lot about the progression of myopia by studying the visual development of baby chickens. They do so by putting little helmets on baby chickens. Lenses on the surface of the helmet cover the chick's eyes and are adjusted to affect how much it can see.

Just like in humans, when visual input is distorted, the chick's eyes grow too large and become nearsighted. And it's progressive. The blur leads to the growth of the eye, which causes the blur to get even bigger, the eye to get even bigger, and so on.

Two recent studies featuring large-scale surveys of children and their parents show that a key factor in the increase in myopia is that people focus on objects in front of them, such as screens, books, and screens. This strongly supports the idea that people are spending a lot of time on drawing pad. The longer you spend focusing on something within an arm's length of your face, known as your “near work,” the more likely you are to become myopic.

So while people may blame new technology like smartphones and too much “screen time” for being bad for our eyes, in reality, even activities as valuable as reading a good book can actually be harmful to our eyes. , may affect vision.

Outdoor light prevents myopia

Other studies have shown that this unnatural eye growth can be inhibited by sunlight.

For example, a 2022 study found that children who did not spend much time outdoors (e.g., once or twice a week) had more than four times the myopia rate compared to children who were outdoors every day. It turns out. At the same time, children who read for more than three hours a day or looked at a screen close up while not in school were four times more likely to be nearsighted than those who spent an hour or less a day.

In another 2012 paper, researchers conducted a meta-analysis of seven studies that compared time spent outdoors and the incidence of myopia. They also found that the more time people spent outdoors, the lower the incidence and progression of myopia. The probability of developing myopia decreased by 2% for every hour he spent outdoors per week.

Other researchers have reported similar effects, arguing that we need to spend more time outdoors and change early childhood schooling to reduce the prevalence of myopia.

What is causing the outbreak?

That still doesn't explain why it's increasing so quickly.

Globally, this is largely due to the rapid development and industrialization of East Asian countries over the past 50 years. Around that time, young people began to spend more time in the classroom reading books and concentrating on other objects near their eyes, and less time outdoors.

This is also what researchers observed in the North American Arctic, where schooling was compulsory for indigenous peoples after World War II. Inuit myopia rates were in the single digits before the 1950s, but rose to over 70% in the 1970s when all children first started attending school.

Countries in Western Europe, North America, and Australia have seen increases in myopia rates in recent years, but the situation falls short of what has recently been observed in China, Japan, Singapore, and several other East Asian countries. The two main factors that have been identified as leading to increased myopia are increased reading and other activities that require focusing on objects close to the eyes, and decreased time spent outdoors.

Because it takes time for young people currently diagnosed with myopia to experience the most severe visual impairment, the worst effects of the rapid increase in myopia cases will likely be 40 or 50 years from now.

treatment of myopia

Fortunately, using blur-correcting glasses or contact lenses for a few minutes each day can stop the progression of myopia. Therefore, early vision testing and vision correction are important to prevent the progression of myopia. Some countries, such as the United Kingdom and now China, require vision tests for children, as do most states in the United States.

However, people with high myopia have an increased risk of blindness and serious eye diseases such as retinal detachment, where the retina separates from the back of the eye. The chance of macular degeneration associated with myopia increases by 40% for each diopter of myopia. A diopter is a unit of measurement used in eye prescriptions.

However, there appear to be two reliable ways to offset or slow down these effects. Spend less time focusing on things near your face, like a book or smartphone, and more time outdoors in bright natural light. Given that the first advice is difficult for modern man to accept, the next best thing might be to take frequent breaks or spend more time reading or scrolling outdoors in the sun. yeah.

(Andrew Herbert is at Rochester Institute of Technology)