Which type of lens might require the use of a push-up technique to evaluate movement?

The push-up technique is typically employed to evaluate the movement of contact lenses on the eye. This technique involves gently pushing on the lower eyelid to observe how the lens moves in response. In the context of contact lenses, thin hydrogel lenses are highly flexible and can easily conform to the shape of the cornea while providing a good level of comfort.

When assessing a thin hydrogel lens, using the push-up technique can help determine how well the lens maintains its position during blinks and how much movement is present, which is essential for both comfort and visual acuity. A lens that moves adequately indicates proper fit, while too little movement may suggest that the lens is too tight, and excessive movement could indicate that it is too loose.

Hard gas permeable lenses, scleral lenses, and rigid gas permeable lenses generally have different fitting parameters and responses than thin hydrogel lenses, making the push-up technique less applicable or necessary in those cases. Thus, the thin hydrogel lens is the type that particularly benefits from this evaluation method.