What type of astigmatism is indicated by a fluorescein pattern showing a concentration of fluorescein inferiorly and superiorly beneath a rigid contact lens?

The presence of a fluorescein pattern that shows a concentration of fluorescein inferiorly and superiorly beneath a rigid contact lens indicates with-the-rule astigmatism. This type of astigmatism is characterized by the vertical meridian having a steeper curvature compared to the horizontal meridian.

When a rigid lens is placed on the eye, it creates a reservoir of fluorescein that pools in areas where the tear film is thinnest—typically in the steepest portions of the cornea. In with-the-rule astigmatism, since the vertical meridian (or steepest part) is more pronounced, one would observe the fluorescein pooling more at the top and bottom of the lens, leading to the concentration pattern seen.

This pattern differs substantially from against-the-rule astigmatism, where the horizontal meridian is steeper, leading to a fluorescein pattern that is more concentrated horizontally. Irregular astigmatism would present a more chaotic fluorescein pattern that does not follow the typical symmetric pooling characteristics of regular astigmatism, while compound astigmatism describes a scenario involving both with-the-rule and against-the-rule components but does not specify the pooling pattern you would observe. Therefore