What is defined as astigmatism where the vertical meridian is steeper than the horizontal meridian?

The term that describes astigmatism characterized by a steeper vertical meridian compared to the horizontal meridian is known as "with-the-rule astigmatism." In this condition, the curvature of the eye leads to blurred vision primarily in the horizontal direction because the steepest curvature is aligned vertically.

With-the-rule astigmatism typically occurs when the vertical meridian is more sharply curved, which affects how light is focused on the retina. Clinically, this means that the patient may have difficulties seeing clearly in horizontal lines or when looking at objects where horizontal resolution is critical, as the eye can focus better on vertical lines due to the different meridian curvatures.

Other forms of astigmatism, such as against-the-rule astigmatism, present with the opposite condition where the horizontal meridian is steeper than the vertical, affecting vertical lines more significantly. Mixed astigmatism involves both steep and flat meridians in different orientations, leading to a more complex visual disturbance. Simple astigmatism refers to a situation where one meridian is normal, while the other is either myopic or hyperopic, without defining a specific orientation. Understanding these definitions and relationships between different types of astigmatism is essential