<Things you should know> The correct knowledge about astigmatism: Causes, symptoms, and treatments for astigmatism What is astigmatism? Types of astigmatism and their main causes Main symptoms caused by astigmatism Treatment methods for astigmatism Astigmatism Self-Check Common problems associated with astigmatism (Q&A) Astigmatism can cause lines to appear blurred or doubled. Many people may not even realize they have astigmatism. This article explains how astigmatism works, providing accurate information about its causes, symptoms, and treatment options. What is astigmatism? Astigmatism is a condition in which the focus of an object does not converge to a single point when viewing it.Astigmatism is a condition where the retina cannot focus properly, causing symptoms such as double vision, blurred vision, and distorted vision. While the degree varies from person to person, it is generally believed that almost everyone has some degree of astigmatism. Types of astigmatism and their main causes There are two types of astigmatism: "regular astigmatism" and "irregular astigmatism." Regular astigmatism is caused by the original shape of the cornea or lens, while irregular astigmatism is mainly caused by eye injury or disease. Regular astigmatism Our eyes have a structure similar to a camera. The cornea and lens, which act as lenses, refract incoming light and focus it to a single point, allowing us to see a focused image. If the cornea and lens are perfectly spherical, the focus will be at a single point at the back of the eye. On the other hand, if they are elliptical, like a rugby ball, there will be directions with gentler curves and directions with sharper curves, preventing the focus from being at a single point."Regular astigmatism" is a condition in which the cornea or lens is tilted in one direction—up, down, left, right, or diagonally—resulting in an inability to focus at a single point. A characteristic symptom is that even when trying to focus on the retina, certain lines are clearly visible, but lines that intersect them at a right angle are difficult to see. Image of regular astigmatism Cornea without astigmatism A beautiful sphere Cornea with astigmatism Oval shape like a rugby ball When the cornea and lens are nearly perfectly round, light is focused almost to a single point.However, because the shape is elliptical, the refraction of light differs vertically, horizontally, and diagonally, so the light does not converge to a single point. Among regular astigmatisms, when the cornea is shaped like a rugby ball placed on its side, it's called "direct astigmatism"; when it's vertical, it's called "inverse astigmatism"; and when it's diagonal, it's called "oblique astigmatism." Each type results in different visual effects. Astigmatism This type of astigmatism resembles a rugby ball lying on its side, with the top and bottom flattened. It is the most common type of astigmatism. Vertical lines are clearly visible, but horizontal lines appear blurred. astigmatism This type has a vertically elongated shape, with both sides flattened. Horizontal lines are clearly visible, but vertical lines are difficult to see. Oblique astigmatism This type of vision is characterized by a slanted cornea or lens. Diagonal lines are easily visible, while lines that intersect those lines at a right angle are difficult to see. How things look when nearsightedness or farsightedness is corrected. Also, a common characteristic of all types of astigmatism is a tendency to experience difficulty seeing in dark places or at night. Lights such as cityscapes, traffic lights, and streetlights may appear blurred or distorted.While many people experience similar symptoms in both eyes, some only experience symptoms in one eye. Additionally, some people have regular astigmatism in one eye and inverse astigmatism in the other. Irregular astigmatism Astigmatism is a condition where irregular bumps or distortions occur on the surface of the cornea, making it difficult to focus. When looking with one eye, objects often appear blurry and doubled.The main causes include corneal damage from external impacts or inflammation of the cornea. It can also be caused by underlying diseases. Image of irregular astigmatism Main symptoms caused by astigmatism With mild astigmatism, there are usually no symptoms, but with severe astigmatism, you may experience changes in your vision, such as distorted or blurred vision, increased sensitivity to light, difficulty seeing bright lights, and even shoulder stiffness and headaches. You may also have trouble seeing small print or numbers, leading to more mistakes and decreased efficiency at work or school.Furthermore, in children, if astigmatism that interferes with daily life is not corrected, it can lead to amblyopia (lazy eye). Treatment methods for astigmatism The treatment methods differ for regular astigmatism and irregular astigmatism. If astigmatism doesn't particularly affect your vision, you don't need to do anything special. However, if astigmatism is causing you trouble with blurred vision, you can correct it with glasses or contact lenses for astigmatism. This method involves wearing lenses that create a curve in the opposite direction to the curvature of the cornea, thus counteracting the original curvature of the eye.If your corrective lenses aren't properly fitted, you might experience eye strain or discomfort, so it's best to have your eyes examined and get a prescription from an ophthalmologist. On the other hand, irregular astigmatism is caused by an uneven corneal surface, making it impossible to correct vision with glasses or soft contact lenses. In most cases, it is corrected with hard contact lenses. The tears that fill the space between the hard contact lens and the cornea cover the unevenness.If correction is not possible even with hard contact lenses, surgery may be performed. Astigmatism Self-Check Please look at the diagram below with one eye at a time. If you notice differences in the darkness or thickness of the lines depending on the angle, you may have astigmatism. Please consult an ophthalmologist. Common problems associated with astigmatism (Q&A) When is the best time to start correcting astigmatism? In children, if severe astigmatism that could lead to amblyopia is detected, it should be corrected immediately. Even mild astigmatism can negatively impact learning by making it difficult to accurately recognize kanji characters or misreading small numbers and letters, so early correction is recommended once children enter school age.Even adults may experience decreased work efficiency due to astigmatism, such as frequently misreading numbers and letters, or taking a long time to read accurately. In such cases, correcting your eyesight is recommended. How can I detect astigmatism in my child? It is often discovered during the eye examination at the 3-year-old health checkup.In addition, the following may be observed: Squinting They are more sensitive to bright light than other people. Furthermore, if you are unable to write numbers or kanji characters despite looking clearly, astigmatism may be suspected. You should consult an ophthalmologist. 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