Because the eyeball is too long (axial length is too long) or the refractive power is too strong, distant images are focused in front of the retina instead of on the retina, causing distant scenes to be blurred. As shown in the figure below, in contrast, hyperopia means that distant images are focused behind the retina. This is because after the light enters the eyeball, the image cannot be focused normally on the retina. Therefore, myopia, hyperopia, and astigmatism are also classified as refractive errors.