What condition describes the inability of the eye to focus light correctly due to irregularities in shape?

The condition that describes the inability of the eye to focus light correctly due to irregularities in its shape is astigmatism. In astigmatism, the cornea or lens has an uneven curvature, which causes light rays to focus on multiple points, leading to blurred or distorted vision. This irregularity prevents light from converging at a single focal point on the retina, resulting in a compromised visual experience for the affected individual.

The other conditions mentioned relate to focusing issues but in different ways. Ametropia is a broader term that encompasses all types of refractive errors, including myopia (nearsightedness), hyperopia (farsightedness), and astigmatism itself. Myopia refers specifically to a condition where distant objects appear blurry due to the eye being too long or the cornea being too steep, thus focusing light in front of the retina. Presbyopia is associated with aging and affects the eye's ability to focus on close objects, primarily due to the loss of flexibility in the lens. Each of these conditions has distinct characteristics, but astigmatism specifically highlights the irregular shape of the eye impacting light focus directly.