Which keratometer reading indicates with the rule astigmatism?

With-the-rule astigmatism occurs when the cornea is steeper along the vertical meridian compared to the horizontal meridian. This type of astigmatism is characterized by a greater power reading in the 180-degree meridian than in the 90-degree meridian, which corresponds to the typical orientation of the human eye.

In the scenario presented, the keratometer reading C shows readings of 44.50 at 15 degrees and 44.75 at 105 degrees. Analyzing these readings, we observe that 44.75 (the steeper reading) is recorded at 105 degrees, while 44.50 (the flatter reading) is at 15 degrees. The reading at 105 degrees is closer to the vertical orientation, confirming that this is indeed an instance of with-the-rule astigmatism.

The other options present different configurations of astigmatism. For instance, the first choice illustrates greater power in a configuration that would be categorized as against-the-rule astigmatism, as it shows a steeper curvature at the horizontal meridian. The second option also demonstrates a similar relationship but with different degrees that do not align with the criteria for with-the-rule astigmatism. The