What characterizes hard contact lenses?

Hard contact lenses are characterized by being rigid gas permeable (RGP). This means that they are made from a type of plastic that allows oxygen to pass through the lens to the eye, which is essential for maintaining eye health and comfort. Unlike soft lenses, RGP lenses maintain their shape on the eye and do not conform to the eye’s surface, which can be beneficial for vision correction as they provide a crisp and clear visual acuity due to their stable shape.

The rigidity of these lenses allows for a smooth surface that is less susceptible to proteins and lipids that can build up on the surface over time, providing a longer wear time without compromising clarity. Additionally, RGP lenses can last longer than soft lenses, contributing to their durability, making them a preferred choice for certain patients, especially those with specific vision needs.

The other answer choices do not accurately reflect the characteristics of hard contact lenses. For instance, being made from flexible materials pertains to soft contact lenses, and the ability to adapt to the shape of the eye applies to soft lenses rather than rigid ones. Additionally, hard contact lenses are generally considered more durable compared to soft lenses, which are more prone to tearing and damage. Thus, the statement about their rigidity (as well as gas