In a standard eye, the cornea and lens have a perfectly even curve, allowing them to focus light onto a single point on the retina at the back of the eye. With astigmatism, these surfaces have mismatched curves. This irregular shape causes light to bend unevenly and focus on —some in front of the retina and some behind it—resulting in a blurred or "smeared" image. Key Symptoms

Beyond general blurriness, people with astigmatism often experience specific visual distortions: Astigmatism - Symptoms & causes - Mayo Clinic

Astigmatism is a common eye condition that causes blurred or distorted vision because the eye isn't perfectly round. While a "normal" eye is shaped like a basketball or a smooth sphere, an eye with astigmatism is shaped more like an , a rugby ball, or the back of a spoon. The Mechanics of Blur