what are the human vision including the structure of the eye, the formation of images by the eye, and common defects of vision? What is the general shape of an eyeglass lens used to correct myopia? What general lens shape would correct hyperopia? and How would these lens shapes be altered if an astigmatism correction was added

what are the human vision including the structure of the eye, the formation of images by the eye, and common defects of vision? What is the general shape of an eyeglass lens used to correct myopia? What general lens shape would correct hyperopia? and How would these lens shapes be altered if an astigmatism correction was added