<Things you should know> The correct knowledge about "myopia": Causes and countermeasures for "myopia" Myopia Causes of nearsightedness Diseases caused by nearsightedness Things to keep in mind to prevent nearsightedness and maintain eye health Recently, myopia has been rapidly increasing worldwide. The increase is particularly significant in East Asia, including Japan, and the WHO (World Health Organization) is calling for urgent action to address the growing global population of myopia.The age at which vision deteriorates is also getting younger; in Japan, the number of elementary school students with uncorrected visual acuity below 1.0 has approximately doubled compared to 1979 (Ministry of Education, Culture, Sports, Science and Technology, "School Health Statistics Survey").How should we cope with nearsightedness?An ophthalmologist will explain the causes and treatments for nearsightedness, providing accurate information and the latest developments. Myopia Our eyes are in their most relaxed and natural state when we are looking at objects more than 5 meters away. Eyes that can form a good image on the retina (i.e., in focus) in this state are called "emmetropia" (normal vision).In contrast, "myopia" occurs when the image is formed in front of the retina in a relaxed state. Distant objects appear blurry, and the focus is on something close up. There are several types of nearsightedness, but most cases are caused by the axial length of the eye, also known as the "axial length," being longer than that of a normal eye. The axial length of a normal Japanese person's eye is said to be about 24 mm. In addition, some cases of nearsightedness are caused by excessive refractive power of the cornea or lens. The difference between normal vision and nearsightedness (axial myopia) In the case of normal vision In the case of myopia (axial myopia) Severity of nearsightedness The degree of nearsightedness is expressed in units called diopters (D).The shorter the distance to an object that can be clearly seen with the naked eye (focal length), the higher the numerical value. Myopia with a focal length of 1m is -1D, myopia with a focal length of 50cm is -2D, and myopia of -6D or higher is called "high myopia". Diopter (D) focal length -1D 1m -2D 50cm -3D 33cm It was previously believed that myopia would stop progressing once one reached adulthood, but in recent years, it has become clear that people with severe myopia continue to experience eye axial lengthening and progression of myopia even after reaching adulthood. Furthermore, it has been reported that severe myopia increases the risk of eye diseases that can lead to blindness. Causes of nearsightedness Myopia occurs during the development of the eye.Newborn babies have small eyeballs, with an axial length (depth of the eyeball) of about 17mm, and most have mild hyperopia (farsightedness). They can only see blurryly. From there, as the body and brain grow, the eyeball, cornea, and lens grow, and visual acuity approaches 1.0 around the age of 5. The length of the axial length generally becomes about 24mm by the age of 13, and it is said that the growth of the axial length stops once the growth period is over. However, if the axial length grows too long due to some influence, it results in myopia (nearsightedness). Hyperopia (baby's eyes) Because the axial length of the eye is short, the focus is achieved behind the retina.The baby's eyes are in this "farsighted state". Direct vision The axial length of the eye is standard (approximately 24 mm). When the eye is relaxed, the image is perfectly focused on the retina. myopia Due to an excessively long axial length of the eye, the focus is in front of the retina in a relaxed, natural state. Near vision is possible, but distant vision is blurry and difficult. It is believed that both genetics and lifestyle factors influence the onset and progression of myopia. Furthermore, children with the following characteristics are considered to be at high risk of developing myopia: Children like this are at high risk of myopia. Parents are nearsighted I don't play outside very often. Going to bed late Short sleep duration Reading a book at a distance of 30 cm or less Playing smartphone or video games for more than an hour straight I'm often in the classroom during school breaks. In rare cases, severe myopia may be present from early childhood (around age 3). Since this can sometimes be accompanied by other medical conditions, early detection and appropriate treatment are essential. Diseases caused by nearsightedness It is said that the earlier someone develops nearsightedness, the more severe their nearsightedness will become.Furthermore, severe myopia stretches and thins the retina, optic nerve, and choroid (the outer layer of the retina), putting strain on nerves and cells and making them more susceptible to various disorders. Diseases that increase the risk of blindness as nearsightedness progresses. Optic nerve damage Glaucoma myopic maculopathy Retinal detachment retinal separation Choroidal retinoretinopathy For people with severe nearsightedness, it is important to have regular eye examinations at an ophthalmologist. Things to keep in mind to prevent nearsightedness and maintain eye health Measures to combat nearsightedness It is common to correct vision using glasses or contact lenses.Leaving vision problems untreated can significantly impact your life, leading to decreased work efficiency and safety issues while driving. In children, it can affect their mental development, causing them to stop reacting to their parents' faces because they can't read their parents' expressions, and making it difficult for them to take an interest in their surroundings. They may also fall behind in class because they can't read the blackboard. If your visual acuity falls below 0.7 in both eyes, it is recommended to correct your vision with glasses or other corrective lenses.Even after getting glasses or contact lenses, your eye condition changes over time. To properly understand the condition of your eyes, you should visit an ophthalmologist regularly. Many people believe that nearsightedness can be cured, but unfortunately, this is a misconception. It is not possible to shorten the axial length of the eye, which has already lengthened.However, mild nearsightedness can also be seen as "eyes suited to modern life." Because the eyes are able to focus on nearby objects, it's easier to read text in books and on computers, making it easier to concentrate on work and studying.Instead of thinking, "I have to cure my nearsightedness," it's better to live with it by making adjustments as needed to suit your lifestyle and the condition of your nearsightedness. Things to keep in mind to maintain eye health This isn't just about nearsightedness, but taking measures to prevent eye strain is important for maintaining eye health. Try paying attention to the following things in your daily life: Spend 2 hours a day, 14 hours a week, outdoors. When watching TV, reading a book, or using your smartphone, make sure the room is well-lit (use a desk lamp in addition to the room light). When doing desk work, sit with correct posture. When doing desk work, adjust the height of your chair and desk so that you can sit with correct posture. Avoid reading books or using smartphones while lying down (as this puts strain on only one eye). If you keep looking at things close up, take a break and look at things far away or look outside. Make regular sleep and a regular daily rhythm a habit. Get enough sleep. Take antioxidants such as "crocetin". *Crocetin is a type of carotenoid, related to beta-carotene found in carrots and lycopene found in tomatoes, and is attracting attention as a substance with antioxidant properties. Supervised by: Dr. Masayoshi Kajita, Director of Kajita Eye ClinicAfter graduating from Fukushima Medical University in 1983, he worked as a researcher at the University of California, Berkeley, before opening Kajita Ophthalmology Clinic in 2003. From 2018 to 2021, he served as a Clinical Professor at Tokyo Medical and Dental University School of Medicine. In 2022, he was awarded Honorary Membership by the Japan Contact Lens Society, and in 2023, Honorary Membership by the Japanese Society of Ophthalmic Optics. He currently serves as a councilor of the Japan Ophthalmological Society and a member of the drafting committee for the Japanese Medical Optics JIS standards. We take care to post accurate information,Please point out any incorrect information. Please submit any comments regarding medical information here. Return to the list of eye symptoms and diseases