Which type of contact lens is designed to fit tightly on the cornea and allows tear exchange beneath the lens?

The type of contact lens designed to fit tightly on the cornea while allowing for tear exchange beneath the lens is rigid gas permeable (RGP) lenses. These lenses are crafted from durable materials that are permeable to oxygen, which is essential for maintaining corneal health. Because RGP lenses are rigid, they create a meniscus of tears beneath the lens that allows for continuous cleansing and replenishment of the tear film. This facilitates improved comfort as well as better vision correction, especially for patients with certain types of astigmatism or other refractive errors.

In contrast, soft contact lenses are generally more flexible and may not provide the same degree of tear exchange beneath the lens. While they can also allow for oxygen transmission, their fit and design differ significantly from RGP lenses. Hybrid lenses combine features of both RGP and soft lenses, providing central RGP portions for clear vision and soft edges for comfort, but they do not offer the same tight fit on the cornea. Scleral lenses are larger and vault over the entire corneal surface, sitting on the sclera instead, which is a different fitting approach that does not offer the same tight relationship with the cornea as RGP lenses do.