Final answer:
An eyeball with a longer axial length is a sign of myopia, commonly corrected with concave lenses or reshaping the cornea to a smaller curvature.
Step-by-step explanation:
An eyeball with a longer axial length is typically indicative of myopia, or nearsightedness. This condition occurs when light entering the eye is focused in front of the retina rather than directly on it, due to the increased length of the eyeball. To correct myopia, the use of a concave lens is often prescribed, as it helps to diverge the light rays slightly so that they can be focused on the retina, providing a clear image.
When correcting myopia via surgery or contact lenses, the cornea's curvature is typically made smaller, which helps to reduce the eye's converging power, allowing images to be focused properly on the retina. This is in line with how a concave lens works, which is curved inward to adjust the focus of images. In contrast, hyperopia or farsightedness occurs when images are focused behind the retina and is corrected with a convex lens, which has the opposite effect, converging light rays to compensate for an eye that is too short.