Oxygen permeability of the pigmented material used in cosmetic daily disposable contact lenses

Abstract

Purpose: To evaluate the individual contributions of pigment colorant and packing solution containing polyvinyl pyrrolidone (PVP) on the oxygen permeability (Dk) of a cosmetic printed etafilcon A daily disposable contact lens packaged with PVP.

Method: The oxygen transport of a contact lens is evaluated through the central optical zone of the lens. Cosmetic printed contact lenses contain pigment colorant in the periphery or mid-periphery of the lens. Therefore, to assess the impact of cosmetic print on oxygen permeability, special lenses need to be produced that contain the colorant within the central optical zone. This technique was used to obtain multiple measurements of nonedge-corrected Dk/t of both the center pigmented lens and its nonpigmented equivalent, using a polarographic measurement described in International Organization for Standardization (ISO) 18369-4:2006(E), and the Dk derived for each measurement is corrected for edge effect. In addition, the edge-corrected Dk values of lenses made from the same monomer batch were measured. The lenses were packaged and autoclaved with and without proprietary technology which embeds PVP in the contact lens during autoclaving. The resulting Dk value of the printed lens material was then used with thickness data to generate true Dk/t profiles for a given lens power.

Results: The edge-corrected Dk of the printed etafilcon A lens with offset pigment colorant was measured to be 19.7×10^-11 (cm²/s) (mL O₂/mL·mmHg) at 35°C. This was within ±20% tolerance range as specified in ISO 18369-2:2012(E) for the edge-corrected Dk of the nonpigmented etafilcon A control lens evaluated during the same session, 19.5×10^-11 (cm²/s) (mL O₂/mL·mmHg). The edge-corrected Dk values of the lenses packaged with PVP (mean 20.1, standard deviation [SD] 0.3) were also within the ±20% tolerance range compared to those packaged without PVP (mean 20.0, SD 0.3).

Conclusion: The pigment colorant and PVP embedded in the contact lens during autoclaving were not found to influence the oxygen permeability of the etafilcon A material.

Keywords: Dk; cosmetic contact lenses; hydrogel contact lenses; oxygen; oxygen permeability.

Figure 1

Thickness profile of a currently marketed −1.00 D cosmetic print contact lens (1-Day Acuvue^® Define^®). Note: Blue boxes indicate the positioning of the colorant.

Figure 2

Lens stack mounted on the polarographic sensor for measurement.

Figure 3

Calculated Dk/t profile of a −1.00D 1–Day Acuvue^® Define^®. Notes: The Dk/t units are 10⁻⁹ (cm/s) (mL O₂ × mmHg). The nominal value of Dk was used in the calculation. Abbreviations: Dk, oxygen permeability; t, thickness of the lens.