What is the primary material used in rigid gas permeable contact lenses?

The primary material used in rigid gas permeable (RGP) contact lenses is silicone acrylate. This material is notable for its ability to allow oxygen to pass through the lens while also providing the durability and stability necessary for clear vision. Silicone acrylate combines the properties of silicone, which enhances oxygen permeability, with acrylate, which contributes to the lens' structural integrity and comfort.

In contrast, the other materials mentioned do not serve as the primary component for RGP lenses. Hydrogel, while commonly used in soft contact lenses due to its water content and comfort, lacks the rigidity required for RGP lenses. Polyethylene glycol is often utilized in various medical and cosmetic formulations but is not a standard material for RGP contact lenses. Polymethyl methacrylate (PMMA) was previously used in older models of hard contact lenses before the advent of gas permeable materials and does not provide sufficient oxygen transmission on its own. Thus, silicone acrylate stands out as the ideal choice for contemporary RGP contact lenses, balancing oxygen permeability with comfort and durability.