Physical Characteristics of Contact Lenses: Oxygen Permeability and Transmissibility

Hello, Ulenspop.com readers. Today, we'll delve into the scientific properties of color contact lenses, focusing on oxygen permeability and transmissibility.

1. Oxygen Permeability (Dk) 🌬️

Oxygen permeability indicates how well the lens material allows oxygen to pass through.

• D: diffusion coefficient of oxygen in the lens material
• k: solubility coefficient of oxygen in the lens material
• Unit: 10⁻¹¹(cm × ml O₂)/(sec × ml × mmHg)

Key features:

• It's a property of the lens material, independent of lens shape or size.
• Permeability increases with temperature.
• It's related to the water content and adhesion of the lens material.
• For soft lenses, higher water content means higher oxygen permeability.
• For RGP lenses, permeability increases logarithmically with material changes.

On average, the highest Dk value for soft lenses is about 40.0, while for RGP lenses it's about 25.

2. Oxygen Transmissibility (Dk/L) 👁️

Oxygen transmissibility represents the amount of oxygen actually delivered to the cornea.

• Formula: Oxygen Transmissibility = Oxygen Permeability ÷ Lens Center Thickness (mm)
• Unit: 10⁻⁹(cm × ml O₂)/(sec × ml × mmHg)

Important points:

• Even with the same material, thicker lenses have lower transmissibility.
• Dk/L (central transmissibility): oxygen transmissibility at the lens center
• Dk/L (average overall transmissibility): average oxygen transmissibility across the entire lens

As average lens thickness increases:

• The center thickness decreases.
• However, the overall lens thickness increases, reducing the actual amount of oxygen delivered to the cornea.

3. Equivalent Oxygen Percentage (EOP) 📊

EOP is the percentage of oxygen in the tear layer between the cornea and lens, compared to atmospheric oxygen.

• The oxygen permeability of all contact lenses corresponds to an EOP of 20.9%.
• EOP is affected by both lens characteristics and the wearer's eye condition.
• Accurate EOP measurement is difficult without disrupting the corneal and tear layer structure.

These scientific properties directly impact the comfort and safety of the color contact lenses you wear. At Ulenspop.com, we consider these factors to provide optimal products.

For more information or inquiries, please don't hesitate to contact us. We're always striving for healthy and beautiful eyes. 🌟👀

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