If a patient has K readings of 43.50 @ 180 and 41.50 @ 90, what could be expected from a spherical GP lens?

In this scenario, the K readings indicate the patient's corneal curvature measurements: the steepest meridian is at 180 degrees with a value of 43.50, and the flattest meridian is at 90 degrees with a value of 41.50. The difference in curvature between these two meridians creates a significant amount of astigmatism, which needs to be considered when selecting a contact lens.

When using a spherical GP lens, which is designed for patients without significant astigmatism, the lens will rest on the cornea in a way that may not align perfectly with the two meridian curvatures. Generally, in the case of astigmatism, a spherical lens can create a situation where it experiences natural destabilizing forces during blinking.

As the eye blinks, the upper eyelid exerts pressure downwards on the lens. Due to the difference in curvature—steeper at the 180-degree meridian—this pressure will generally cause the lens to move downward and possibly slightly inwards or outwards depending on the fit and lens design. Therefore, the expected behavior is that the lens will display movement that is downward and either inward or outward with each blink. This aligns with the anticipated behavior