A Blurry Worldview 

1. In school, have you ever struggled to see what the teacher wrote on the board? Maybe you can easily read from a book, but things further away—like road signs—look blurry. This blurry distant vision is the main symptom of myopia, a condition that affects many children and adults. If you have myopia, you’ll have trouble seeing things far away, but you’ll be able to see nearby things clearly. This is why myopia is commonly called shortsightedness. Other symptoms of myopia include headaches, eyestrain and squinting. 
2. Myopia typically begins in childhood. ‘Children often don’t realise they are myopic’, says Dr Mary Frances Cotch of America’s National Eye Institute, ‘because myopia develops gradually and they don’t have any way of knowing that their blurry vision is different from others’.’ In most cases, the degree of shortsightedness stabilises by the time a person reaches adulthood. Some people, however, may have myopia that continues to worsen with age. 
3.  So what causes this vision problem? Consider how the eye works. When you look at an object, the light rays of that object pass through the outermost layer of the eye (the cornea) and the lens. The cornea and the lens refract, or bend, the light and focus it on the light-sensitive tissue at the back of the eye (the retina). If you have perfect vision, the rays focus directly on the surface of the retina. In a myopic eye, the eyeball is usually too long from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. This makes distant objects appear blurry. 
4. Myopia can also be the result of a cornea that is too curved or a lens that is too thick. For some, myopia is caused by a combination of these problems. 
5. What causes the eyeball to grow too long isn’t completely known, but researchers are exploring several possibilities. For many people, myopia appears to be inherited, so if you have a parent with myopia, you’re at increased risk of developing it yourself. 
6.  Myopia is becoming increasingly common in many countries around the world. In a study published in 2008, experts found that the number of Americans with myopia increased significantly from the 1970s to the early 2000s. And myopia is especially prominent among school-age children living in urban areas in some Asian countries
7. Researchers are looking to see if and how myopia might be related to a person’s sex, age, ethnicity and environmental exposures—such as sunlight or the amount of time spent doing close-up work. In the past, experts thought that myopia might arise in children who spent too much time indoors reading and writing—activities that require close-up vision—or from reading in poorly lit rooms. Recent studies, however, suggest that increased myopia in children might instead be related to kids spending less time outdoors. Continued investigation into how myopia develops will help researchers more precisely determine the potential causes and influences. 

Adapted from NIH News in Health, ‘A Blurry Worldview: Understanding Myopia’