What indicates that a prescription corrects for Against-the-Rule Astigmatism?

When determining the correct answer for what indicates a prescription corrects for Against-the-Rule Astigmatism, it's important to understand the characteristics of astigmatism and how they relate to the orientation of the primary focal lengths and the cylinder axis.

In Against-the-Rule Astigmatism, the steepest meridian is situated horizontally (i.e., along the 180-degree line), while the flattest meridian is vertical (along the 90-degree line). This configuration suggests that the corrective cylinder should be placed with its axis within 30 degrees of the vertical meridian (90 degrees) and in minus cylinder form. The answer indicates that the shortest focal length is vertical, which complements the definition of this type of astigmatism, because the vertical meridian (where the correction is applied) is indeed where the short focal length lies.

Hence, having the shortest of the two primary focal lengths as vertical and in minus cylinder form, with the axis aligned within 30 degrees of the 90 meridian, accurately corresponds to correcting Against-the-Rule Astigmatism. This is key in ensuring that the correction effectively addresses the steepest and flattest meridians of the eye involved in this type of astig