Given a spectacle RX of -2.00 -1.50 x090, what issue should a contact lens fitter be alert to based on the information "K" 41.00@180/44.50@90?

The issue that a contact lens fitter should be alert to based on the provided spectacle prescription and keratometry readings is residual astigmatism. In this case, the spectacle prescription indicates that the patient has a significant amount of astigmatism (-1.50 diopters) and also details a specific corneal curvature with two different readings (41.00 at 180 degrees and 44.50 at 90 degrees).

When fitting contact lenses, especially toric lenses designed to correct astigmatism, it is essential to consider the difference between the refractive astigmatism measured in the spectacle prescription and the corneal astigmatism indicated by the keratometry readings. Residual astigmatism occurs when the lens does not fully correct the astigmatism present in the eye, leading to ongoing visual distortion. In this case, because there is a notable difference between the corneal curvature readings and the astigmatic correction required, the potential for residual astigmatism exists, resulting in visual issues for the patient even after fitting the appropriate contact lenses.

Thus, understanding both the spectacle prescription and the keratometry measurements is crucial for the contact lens fitter to minimize residual astigmatism and optimize the