The normal eye is shaped like a perfect sphere. The cornea and lens focus incoming light onto the retina on the back of the eye to form an image. With nearsightedness (myopia), the eye is a bit elongated, and the cornea’s curvature is now too steep. As a consequence, light is not coming into sharp focus on the retina itself, but rather at some point before reaching the retina. As the focal point is now in front of the retina, the light on the retina itself is causing images of distant objects to appear out of focus and blurry.
Nearsightedness (myopia): The eye is a bit longer than it should be (axial myopia), or the cornea is excessively curved (curvature myopia).