Spherical contact lenses are a type of hard contact lens that have a sphere shape, with the lens center being surrounded by a concentric ring of curvature. They are designed to replace the cornea of the eye and correct vision problems such as nearsightedness, farsightedness, and astigmatism. Spherical contact lenses typically have a diameter of around 13mm and are worn by placing them on the fingertip and sliding them onto the cornea. They are usually available in prescriptions ranging from -8 to +8 diopters and can last up to one month with proper care.