What does "Scleral Lens" refer to?

"Scleral lens" specifically refers to a large-diameter gas-permeable contact lens that is designed to vault over the cornea and rest on the sclera, which is the white part of the eye. These lenses create a tear-filled space between the lens and the cornea, providing comfort and vision correction for individuals with irregular corneas, severe dry eye, or other ocular surface diseases.

The unique design of scleral lenses allows them to distribute pressure evenly across the eye's surface, which can be particularly beneficial for patients who cannot wear standard contact lenses due to corneal irregularities or sensitivities. This vaulting effect also protects the cornea by creating a cushion of tears, promoting healing and comfort.

The other options describe different types of lenses that do not fit the specific characteristics of scleral lenses. A small-diameter rigid lens would typically refer to traditional gas-permeable lenses that do not vault over the cornea. Easily disposable soft lenses are generally designed for convenience and wearability, while options specifically for astigmatism would typically refer to toric lenses that are distinct from the design and function of scleral lenses. Thus, the characteristics of option B accurately encapsulate what a scleral lens is.