IPC's are used to:

Interpalpebral curves (IPC) are indeed designed to provide a transition between the peripheral and base curves of contact lenses. This transition is essential because it helps in creating a more seamless fit and facilitates the natural movement of the lens with the blink. By properly integrating the IPCs, contact lenses can conform better to the shape of the eye, enhancing comfort and stability during wear.

In this context, the smooth transition achieved by IPCs allows for a more gradual change in lens curvature, which can improve the overall wearing experience. This design feature is particularly important for maintaining consistent tear exchange beneath the lens and ensuring that the lens remains centered on the cornea during eye movements.

While the other options might represent features or considerations relevant to contact lens design, they do not accurately define the specific function of IPCs. For example, reducing edge thickness and lens mass focuses on the physical properties of the lens, while increasing the optical zone pertains more to the lens's visual performance and design. Likewise, smoothing the lens edge addresses comfort but does not specifically relate to the role of IPCs. Thus, the identification of IPCs as a means to provide a transition between curve profiles is key to understanding their purpose in contact lens fitting and design.