Corneal contact lenses
These are contact lenses with diameter of 8.5 to 9.5 mm. They are produced as hard contact lenses, either from PMMA, or a copolymer of methyl methacrylate, which is permeable to oxygen – these contact lenses are called “rigid gas-permeable” (RGP) contact lenses. Unlike the scleral contact lenses, corneal contact lenses are better tolerated – their smaller surface area enables better exchange of tear film and also allows the uncovered part of the eye to breathe. Hard corneal contact lens with rounded edges and adequate movement of the eye does not cause conjunctival hyperemia, as they do not come in contact with the conjunctiva.