What are the two types of lenses commonly used in glasses?

The two types of lenses commonly used in glasses are convex and concave lenses. Convex lenses are thicker in the center and thinner at the edges, which allows them to converge light rays. This characteristic makes them useful for correcting hyperopia, or farsightedness, allowing individuals to see distant objects more clearly. On the other hand, concave lenses are thicker at the edges and thinner in the center, spreading light rays apart. This design enables concave lenses to correct myopia, or nearsightedness, helping individuals to see nearby objects more clearly.

While some of the other options represent specific types of lenses that serve particular purposes, such as bifocal and trifocal lenses (which are multi-focal lenses designed for people requiring multiple prescriptions) or aspheric and cylindrical lenses (which provide varying curvature and are generally used for astigmatism or to reduce distortion), they do not encompass the foundational classifications of lenses that form the basis of vision correction. Thus, convex and concave lenses properly capture the two fundamental types commonly used in standard spectacles.