What kind of astigmatism is characterized by greater power in the vertical meridian?

With-the-rule astigmatism is characterized by greater power in the vertical meridian. In this condition, the curvature of the cornea is such that the vertical meridian is steeper than the horizontal meridian. This results in greater refractive power along the vertical axis, leading to distortion of vision, especially in vertical lines.

With-the-rule astigmatism typically arises due to common shapes of the cornea, and it affects individuals by causing blurred or distorted vision when looking at vertical objects. Recognizing this type of astigmatism is crucial for eye care professionals, as it influences the best corrective measures, such as the prescription of cylindrical lenses that compensate for the additional curvature in the vertical meridian.

In contrast, against-the-rule astigmatism features greater power in the horizontal meridian, irregular astigmatism presents an uneven cornea shape that causes varying curvature in different meridians, and mixed astigmatism combines aspects of both with-the-rule and against-the-rule types. Thus, the specific definition of with-the-rule astigmatism aligns perfectly with the characteristics described in the question.