Which vision condition is primarily characterized by a lack of focus on specific points?

Astigmatism is the vision condition characterized by an irregular shape of the cornea or lens, which leads to a lack of focus on specific points. In a normally shaped eye, light rays converge at a single point on the retina, allowing for clear vision. However, when someone has astigmatism, the uneven curvature causes light rays to focus on multiple points, either in front of or behind the retina, rather than a singular focal point. This results in distorted or blurred vision at any distance, as the eye struggles to concentrate on precise points.

Myopia is related to the eye being too long or the cornea being too steep, causing distant objects to appear blurry. Hyperopia, or farsightedness, occurs when the eye is too short or the cornea is too flat, making near objects difficult to see clearly. Presbyopia is a condition related to aging where the lens loses its flexibility, making it hard to focus on close objects but does not involve distortion of focus across different distances like astigmatism does. Therefore, the defining characteristic of astigmatism is primarily focused on the inability to focus clearly on specific points due to the eye's shape.