Which of the following could cause a patient rigid contact lens to displace frequently and pop out without a cause?

In this case, the correct response indicates that both the excessive posterior peripheral curve and the flat base curve relationship contribute to the frequent displacement and popping out of a rigid contact lens.

A lens with an excessive posterior peripheral curve may not provide adequate stability on the eye, leading to shifts in its position during blinking or movement. If the edge of the lens is too steep, this can create a situation where the lens is prone to dislodging, especially during blinks or movements that cause the lens to catch inappropriately on the eyelid.

On the other hand, a flat base curve relationship implies that the curvature of the lens base is too flat relative to the corneal shape of the patient. This mismatch can limit the lens's ability to conform and adhere to the surface of the eye, causing it to shift more easily under everyday activities, which also makes it prone to dislodgment.

In contrast, insufficient peripheral curve typically leads to issues like discomfort or inadequate tear exchange rather than direct displacement of the lens. Therefore, while this option does affect lens performance, it does not directly correlate with frequent popping out in the same way that excessive curves and flat base relationships do.

Thus, understanding the balance of curvature and how it impacts fit and stability