Final answer:
Astigmatism is a vision impairment caused by a defective curvature of the eye, leading to asymmetrical focus and blurred images, and can be corrected with eyeglasses that have cylindrical correction.
Step-by-step explanation:
People with astigmatism have impaired vision due to a defective curvature of the eye. Astigmatism is an unevenness or asymmetry in the focus of the eye, often resulting from irregularities in the shape of the cornea, the lens, or the retina. For instance, rays passing through different regions of the eye may focus at different points, causing the image to appear elongated or blurred along certain axes.
This vision defect can manifest as less distinct vision or images that are sharper along one axis than another. Astigmatism can be at least partially corrected with prescription eyeglasses that have a cylindrical correction to counteract the eye's irregularity. While spherical corrections are used for other vision defects like nearsightedness or farsightedness, the cylindrical correction is specifically for addressing astigmatism.