What are the three types of DK materials used in hard contact lenses?

What are the three types of DK materials used in hard contact lenses?

• A. Low-DK, High-DK, Hyper-DK
• B. Medium-DK, Ultra-DK, Mega-DK
• C. Soft-DK, Rigid-DK, Semi-DK
• D. Standard DK, Special DK, Extreme DK

Answer: (B)

Oxygen passes through contact lens material at a rate described by Dk, and for hard lenses the amount of oxygen reaching the cornea is crucial for corneal health. To reflect different material capabilities, clinicians talk about categories of Dk materials, spanning from lower to much higher oxygen permeability. Having three distinct labels helps practitioners match lens choices to a wearer’s needs and wearing schedule. The option that names three levels as Medium-DK, Ultra-DK, and Mega-DK fits this idea of a progression from moderate to very high permeability, providing a simple framework that communicates a spectrum of oxygen transmission in hard lens materials. The other choices introduce terms that aren’t standard descriptors for DK in hard lenses, making them less fitting for this concept.

Oxygen passes through contact lens material at a rate described by Dk, and for hard lenses the amount of oxygen reaching the cornea is crucial for corneal health. To reflect different material capabilities, clinicians talk about categories of Dk materials, spanning from lower to much higher oxygen permeability. Having three distinct labels helps practitioners match lens choices to a wearer’s needs and wearing schedule.

The option that names three levels as Medium-DK, Ultra-DK, and Mega-DK fits this idea of a progression from moderate to very high permeability, providing a simple framework that communicates a spectrum of oxygen transmission in hard lens materials. The other choices introduce terms that aren’t standard descriptors for DK in hard lenses, making them less fitting for this concept.