Small diameter hard contact lenses (also called gas permeable contact lenses) are made of hard plastic and are designed to correct for a variety of prescriptions.
Hard contact lenses were very common 30 years ago but have fallen out of favor as soft lens technology has advanced. These days soft contact lenses can correct for most common refractive error like nearsighted, farsighted, and astigmatism.
While soft lenses may be more comfortable, hard contact lenses offer far better vision. Hard contact lenses do not bend or distort like soft lenses. This results in superior optics and improved quality of vision.
Hard contact lenses are most useful for patients that want the best vision possible or in patients with very high prescriptions. In addition, hard contact lenses are also useful for patients with certain corneal disease like Keratoconus.
Because hard contact lenses do not flex or bend on the eye, they can form a new surface for these patients with disease.
One lens of note is the Rose K2 hard contact lens (pictured). This newer design of an old favorite is a mainstay of treatment for patients with mild to moderate ectasia like Keratoconus.
In addition to small diameter hard lenses, hybrid contact lenses, and scleral contact lenses are also useful for corneal disease.