Which type of RGP lenses are more likely to flex?

The correct answer indicates that minus lenses thinner than 0.13 mm are more likely to flex. Rigid gas permeable (RGP) lenses can demonstrate varying degrees of flex depending on their design characteristics, including thickness and the curvature of the lens. Thinner lenses inherently have less material to resist deformation or bending under physical stress.

In the case of minus lenses, because they are designed to be concave, which contributes to a certain degree of flexibility compared to their plus counterparts, this flexibility is accentuated when the thickness is reduced. Thus, a minus lens that is thinner than 0.13 mm possesses a greater likelihood of flexing when exerted with force, such as when being handled or during wear.

On the contrary, thicker lenses, irrespective of being plus or minus, tend to resist flexing due to the increased material strength and rigidity, making them less likely to flex under normal conditions. This fundamental understanding of lens design and material properties helps clarify why thinner minus lenses exhibit a greater propensity for flexing.