Contact lens oxygen permeability explained as Constar details Dk and Dk/t

Constar says contact lens oxygen permeability is a key factor in corneal health, especially for people who wear lenses for long hours or overnight. The company outlined how Dk and Dk/t work, why silicone hydrogel lenses deliver more oxygen, and what wearers should ask before choosing a lens.

Why it matters: - The cornea gets oxygen directly from the air, not from blood vessels. - A contact lens can restrict that oxygen flow and raise the risk of corneal stress. - Low oxygen delivery can contribute to corneal swelling, blur, halos, discomfort, infection risk, neovascularization, and long-term changes to the cornea. - The Dk/t number is the practical measure wearers should watch, because lens thickness changes how much oxygen reaches the eye.

What happened: - Constar, a Gansu-based contact lens OEM and ODM maker, published an explainer on contact lens oxygen permeability. - The article breaks down Dk, Dk/t, and the science behind corneal oxygen needs. - Constar said its own clear and colored contact lens portfolios are manufactured under ISO 13485 quality systems and tested to ISO 18369-4 for oxygen permeability. - The company said its products include silicone hydrogel daily disposables, monthly lenses, and colored or cosmetic series.

The details: - Dk measures how easily oxygen passes through a lens material. - Dk/t measures oxygen transmissibility and equals Dk divided by lens thickness. - The unit for Dk is the Barrer, expressed as ×10⁻¹¹ cm²/(s·mL O₂/mL·mmHg) at 35°C under ISO 18369-4. - The Holden-Mertz minimums cited in the article are Dk/t of 24.1 for daily wear and 87.0 for overnight wear. - Traditional hydrogel lenses typically have Dk values of 10 to 40 Barrer and Dk/t of about 17 to 35. - Silicone hydrogel lenses typically have Dk values of about 60 to 190 Barrer and Dk/t of about 80 to 180. - The article says silicone hydrogel lenses can deliver up to six times more oxygen to the cornea than traditional hydrogel lenses. - The article says silicone hydrogel lenses accounted for 88.4% of global contact lens revenue in 2021. - The article says only silicone hydrogel lenses with Dk/t above 87 are FDA-approved for overnight or extended wear. - The article says high water content does not automatically mean high oxygen permeability. - The article says oxygen delivery depends more on the lens material than the moisture level on the box. - The article advises wearers to ask for the exact Dk/t value of any prescribed lens. - The article recommends silicone hydrogel for people who wear lenses more than 6 hours a day. - The article recommends daily disposables as a lower-contamination option. - The article says reputable manufacturers should be able to provide Dk test data under ISO 18369. - Constar says the company serves global brands and distributors in more than 40 countries. - Constar says it was founded more than 40 years ago and is headquartered in Baiyin, Gansu Province. - Constar says it operates six production facilities with capacity for more than 15 million lenses per month. - Constar says it holds US FDA 510(k), EU CE 0197 (MDR), TGA, SFDA, AKL, and Class B (Vietnam) certifications.

Between the lines: - The piece is both an educational explainer and a company credential sheet. - The strongest practical message is that lens material matters more than water content when oxygen delivery is the goal. - The article also reflects a broader industry shift toward silicone hydrogel as the default material for longer wear. - The repeated emphasis on testing standards suggests Constar is positioning compliance and manufacturing controls as part of its market pitch.

What's next: - Wearers who need full-day or overnight use are being steered toward silicone hydrogel and away from lower-Dk hydrogels. - Eye care professionals remain the key gatekeepers for choosing the right Dk/t, wear schedule, and replacement plan. - The article points readers to Constar’s product portfolio and ISO 18369-4 testing documentation for more information.