Final answer:
Astigmatism is a defect where an asymmetrical focus due to cornea irregularities causes blurred vision, corrected by cylindrical eyeglass lenses or procedures like LASIK.
Step-by-step explanation:
Understanding Astigmatism and Its Correction
Astigmatism is a common vision defect characterized by unevenness or asymmetry in the eye's focus, resulting in images that appear elongated or distorted. This condition is often caused by irregularities in the shape of the cornea, or less commonly, by irregularities in the eye's lens or retina. These irregularities cause light to focus at different points on the retina, leading to blurred or distorted vision. Astigmatism is frequently observed along certain axes, where vision may be sharper or more blurred in comparison to others. A simple test using a chart can detect the presence of astigmatism, where one might notice that lines along some axes appear darker or clearer than others.
To correct astigmatism, spectacles with cylindrical correction are used, which compensates for the eye's irregular shape. Unlike spherical corrections that address short- or farsightedness uniformly across all axes, cylindrical corrections target the specific meridians of the eye affected by astigmatism. Advanced medical procedures like LASIK can also correct astigmatism by accurately reshaping the cornea, thereby improving vision in a majority of cases.