What is the astigmatism for the Rx -2.00 -2.50 x 180?

In the prescription -2.00 -2.50 x 180, the astigmatism can be determined by analyzing the values of the cylinder and the axis. The spherical component is -2.00 D, while the cylindrical component is -2.50 D, indicating the presence of astigmatism.

To classify astigmatism, the orientation of the cylinder is important. The axis of -2.50 D is at 180 degrees. With astigmatism, we categorize it based on the orientation of the steep meridian. For an astigmatism to be classified as "Against the Rule," it demonstrates that the steepest meridian is horizontal (between 0 and 30 degrees, or 150 and 180 degrees).

In this case, with the axis at 180 degrees, the steepest meridian is indeed horizontal, indicating an "Against the Rule" astigmatism. This type suggests that the cornea is steeper vertically rather than horizontally, which is common.

Therefore, the correct classification of the astigmatism in this prescription aligns perfectly with the characteristics described for "Against the Rule."