Hyperopes should have a lower/higher Dk?

Hyperopes should have a lower/higher Dk?

• A. Lower
• B. Not specified
• C. Same
• D. Higher

Answer: (D)

Oxygen transmission through a GP lens is what keeps the cornea healthy, and it depends on two things: the material’s Dk and how thick the lens is where the eye sits (center thickness). A higher Dk means more oxygen can pass through the lens material each moment. In hyperopic (farsighted) corrections, the plus-power lenses often end up with a thicker center to achieve the required refractive power, which reduces the amount of oxygen that actually reaches the cornea if the material isn’t very permeable. To offset this thicker center and maintain good corneal oxygenation, you want a material with a higher Dk so that oxygen delivery remains adequate despite the increased thickness. That’s why hyperopes are best served by a higher Dk. Using a lower Dk would make the cornea more prone to hypoxic stress, not ideal for long-term comfort and eye health.

Oxygen transmission through a GP lens is what keeps the cornea healthy, and it depends on two things: the material’s Dk and how thick the lens is where the eye sits (center thickness). A higher Dk means more oxygen can pass through the lens material each moment. In hyperopic (farsighted) corrections, the plus-power lenses often end up with a thicker center to achieve the required refractive power, which reduces the amount of oxygen that actually reaches the cornea if the material isn’t very permeable. To offset this thicker center and maintain good corneal oxygenation, you want a material with a higher Dk so that oxygen delivery remains adequate despite the increased thickness. That’s why hyperopes are best served by a higher Dk. Using a lower Dk would make the cornea more prone to hypoxic stress, not ideal for long-term comfort and eye health.