During a fluorescein evaluation of a rigid lens, a fitter observes absence of fluorescein horizontally, with pooling vertically, in a patient with with-the-rule astigmatism. What type of lens would be most appropriate?

In this scenario, the observation of fluorescein pooling vertically with an absence of fluorescein horizontally indicates the nature of the lens fitting issue related to the corneal shape, particularly in the context of with-the-rule astigmatism. With-the-rule astigmatism typically means that the cornea has more curvature along the horizontal meridian than the vertical one.

To effectively correct vision in a patient with this type of astigmatism, a bitoric gas permeable (GP) lens is most suitable. Bitoric lenses have both front and back toricity, allowing them to align with the cornea's shape while providing optimal correction for different meridians of astigmatism. This is important because it helps ensure proper coverage and pooling of the fluorescein, which signals an even fitting across the lens surface.

This choice ensures alignment with the corneal irregularities associated with with-the-rule astigmatism. Other options, like front toric GP or single-cut GP lenses, may not provide the same level of customization necessary for fitting uneven curvatures, leading to poor visual acuity and discomfort.