One of the top questions that I get at The Spectacle Shoppe is, "What is an Astigmatism"? In short, Astigmatism is a common type of refractive error. It is a condition in which the eye does not focus light evenly onto the retina -- the light-sensitive tissue at the back of the eye. Instead of creating one focus point, the rugby ball shaped cornea creates multiple focus points (see diagram). To help illustrate further, I've sourced The National Eye Institutes explanation of the facts on astigmatism.
Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see.
Astigmatism occurs when light is bent differently depending on where it strikes the cornea and passes through the eyeball. The cornea of a normal eye is curved like a basketball, with the same degree of roundness in all areas. An eye with astigmatism has a cornea that is curved more like a football/rugby ball shape (see diagram), with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out.
Astigmatism can affect both children and adults. Some patients with slight astigmatism will not notice much change in their vision. It is important to have eye examinations at regular intervals in order to detect any astigmatism early on for children.
Signs and symptoms include:
If you experience any of these symptoms, visit your eye care professional. If you wear glasses or contact lenses and still have these issues, a new prescription might be needed.
Astigmatism is usually found during a comprehensive dilated eye exam. Being aware of any changes in your vision is important. It can help in detecting any common vision problems. If you notice any changes in your vision, visit your eye care professional for a comprehensive eye dilated examination.
It is possible to have mild astigmatism and not know about it. This is especially true for children, who are not aware of their vision being other than normal. Some adults may also have mild astigmatism without any symptoms. It's important to have comprehensive dilated eye exams to make sure you are seeing your best.