With the rule astigmatism features what type of curvature?

With regular astigmatism, particularly when we say "with the rule," there is a specific characteristic in terms of the curvature of the cornea. In "with the rule" astigmatism, the vertical meridian is steeper than the horizontal meridian.

This means that the curvature is such that it mimics the shape of a football, with the steepest part oriented vertically. As a result, light rays that enter the eye are focused at different points on the retina depending on their axis. The steep vertical meridian causes the eye to have a greater degree of refractive power along that axis. In practical terms, when evaluating and correcting this type of astigmatism, practitioners prioritize the vertical meridian for lens fitting and prescription adjustments.

In cases of "against the rule" astigmatism, the situation is reversed, where the horizontal meridian is steeper. However, since the question specifically addresses "with the rule" astigmatism, it emphasizes the steepness of the vertical meridian. Understanding this aspect is crucial for optometrists and professionals involved in fitting contact lenses or correcting refractive errors.