Astigmatism is a common vision problem that causes blurred vision. It occurs when the cornea (the front cover of the eye) is irregular shaped, meaning that the eye isn’t completely round. The curvature of the lens inside the eye could also be a cause of astigmatism. As a result of the shape of the eye, vision becomes blurred at any distance. A normally shaped cornea is more like the shape of a basketball, allowing light to come in directly to the retina creating crisp, clear images. An eye with astigmatism is more oblong, like a football. It's harder for light to enter properly causing blurred, distorted images. This could result in eye discomfort or even headaches at times.
Astigmatism isn’t a “visible” condition; you won’t notice it with the naked eye. However, some symptoms would include blurred vision, eye strain, squinting to see near or far distances, double vision, and often headaches.
In order to determine if you have Astigmatism, your doctor will perform a comprehensive eye exam by how effectively your eyes focus light on the retina. Some things that the doctor would test for are visual acuity, keratometry, and refraction. Visual acuity is the most common vision test. It is where you read a series of letters on a distant chart with results such as 20/20, meaning perfect vision, while a visual acuity of 20/40 would mean that you are reading letters at 20 feet away that you should be able to see at 40 feet away.
Keratometry is a test used to measure the curvature of your cornea by focusing a circular light on the cornea and measuring its reflection.
Refraction you would use a phoropter to determine the measurement of corrective lenses to give you a clearer vision. The doctor places the phoropter in front of your eyes while showing you a series of lenses to see how you focus light. The final measurement is used to give you a prescription for your glasses to correct your vision for nearsightedness, farsightedness, and astigmatism.