Rigid Gas Permeable (RGP) lenses do not medically "treat" a disease, but they are optical corrective devices used to manage complex vision conditions and corneal irregularities where standard soft lenses fail. They provide exceptionally sharp visual acuity for patients suffering from severe astigmatism, high myopia, presbyopia, and irregular corneal conditions such as keratoconus, post-surgical corneal scarring, and pellucid marginal degeneration.