How Thomas Young discover astigmatism?

Thomas Young discovered astigmatism in the early 19th century through his work on the wave theory of light and the study of vision. He noted that certain lenses, such as cylindrical lenses, could focus light differently along different axes, leading to distorted images. Young's experiments with these lenses and his understanding of how the eye processes light contributed to the recognition of astigmatism as a common refractive error. His findings laid the groundwork for further research into the nature of vision and optical imperfections.