If a patient has a refractive cylinder of 1.50D and keratometer readings of 44.00 @ 180/44.50 @ 90, what outcome would you expect from a spherical gas permeable lens?

The situation involves a patient with a measurable refractive cylinder and specific keratometer readings, which indicate the presence of astigmatism. The refractive cylinder of 1.50D suggests that there is a difference in curvature between the two principal meridians of the cornea, creating astigmatism.

When prescribing a spherical gas permeable lens, it is important to note that these lenses are not designed to correct for astigmatism effectively unless special modifications are made (like using a toric lens). Since a spherical lens does not take into account the different curvatures of the cornea in the two principal meridians, it cannot completely correct the astigmatism.

As a result, while the spherical gas permeable lens may improve vision by addressing the patient's refractive error to some extent (for example, it might improve visual acuity by flattening the overall curvature and reducing aberrations), it will not eliminate the astigmatism entirely. Therefore, residual astigmatism remains after the lens is fitted, which is consistent with the refractive cylinder measurement noted.

This outcome illustrates that while improvements in vision might occur (such as with increased visual acuity), the nature of the lens chosen means that