Polymeric articles comprising oxygen permeability enhancing particles

Abstract

The present invention relates to a composition comprising a hydrogel polymer having less than 100% haze, and distributed therein an oxygen enhancing effective amount of oxygen permeable particles having an oxygen permeability of at least about 100 barrer, average particle size less than about 5000 nm.

Description

RELATED APPLICATIONS[0001]This application claims priority of U.S. Provisional Patent Application No. 61 / 164,931 filed Mar. 31, 2009 and U.S. Provisional Patent Application No. 61 / 252,279 filed Oct. 16, 2009.FIELD OF THE INVENTION[0002]The invention relates to polymeric articles comprising oxygen permeability enhancing particles and processes for forming such articles.BACKGROUND OF THE INVENTION[0003]Polymeric materials displaying oxygen permeability are desirable for a number of applications, including medical devices. One such application is contact lenses.[0004]Gas permeable soft contact lenses (“GPSCL”) have been made from conventional and silicone hydrogels. Conventional hydrogels have been prepared from monomeric mixtures predominantly containing hydrophilic monomers, such as 2-hydroxyethyl methacrylate (“HEMA”), N-vinyl pyrrolidone (“NVP”) and vinyl alcohol. The oxygen permeability of these conventional hydrogel materials relates to the water content of the materials, and is ...

AI Technical Summary

Benefits of technology

[0090]The advancing contact angle was measured using −1.00 power lenses as follows. Four samples from each set were prepared by cutting out a center strip from the lens approximately 5 mm in width and equilibrated in packing solution. The wetting force between the lens surface and borate buffered saline is measured at 23° C. using a Wilhelmy microbalance while the sample is being immersed into or pulled out of the saline. The following equation is used

[0091]The Dk is measured as follows. Lenses are positioned on a polarographic oxygen sensor consisting of a 4 mm diameter gold cathode and a silver ring anode then covered on the upper side with a mesh support. The lens is exposed to an atmosphere of humidified 2.1% O2. The oxygen that diffuses through the lens is measured by the sensor. Lenses are either stacked on top of each other to increase the thickness or a thicker lens is used. The L / Dk of 4 samples with significantly different thickness values are measured and plotted against the thickness. The inverse of the regressed slope is the Dk of the sample. The reference values are those measured on commercially available contact lenses using this method. Balafilcon A lenses (−1.00) available from Bausch & Lomb give a measurement of approx. 79 barrer. Etafilcon lenses give a measurement of 20 to 25 barrer. (1 barrer=10−10 (cm3 of gas×cm2) / (cm3 of polymer×sec×cm Hg)).

[0092]Si content was measured via neutron activation. All samples, standards, and quality controls are irradiated for 15 seconds, allowed to decay for 120 seconds and counted for 300 seconds. The concentration of silicon is determined by measuring the 1779 keV gamma-ray from the decay of 28Al (t1 / 2=2.24 minutes). The 28Al is produced via the (n,p) reaction on 28Si. Three geometrically equivalent silicon standards are analyzed with the sample set. The standards are prepared by spiking paper pulp with silicon from a 10.00±0.05 mg / mL certified solution standard (High Purity Standards). The results are blank corrected for the 28Al signal from the blank high-density polyethylene sample irradiation vial. NIST SRM 1066a Octaphenylcyclotetrasiloxane is co-analyzed with the samples as a quality control check for the analysis. The certified silicon concentration in this SRM is 14.14±0.07 Wt. % Si. The average value for the analysis of three 10 mg aliquots of the SRM was 14.63±0.70 Wt. % Si.

[0093]Surface roughness was measured via AFM using a Digital Instruments Nanoscope, a scan size of 20 μm and a scan rate of 7.181 Hz. For each sample 256 scans were processed and the data scale employed was 1000 μm. The engage X and Y positions were −19783.4 and −42151.3 μm, respectively.

[0094]SEM Surface characterization: Surface images were captured from all samples on both the concave and convex surfaces at three locations (left, middle and right). The imaging was performed using an FEI Quanta Environmental SEM using an accelerating voltage of 25 kV and 5 nA of beam current at 5000× magnification for all locations in SE and BSE imaging modes.

[0095]The Examples below further describe this invention, but do not limit the invention. They are meant only to suggest a method of practicing the invention. Those knowledgeable in the field of contact lenses as well as other specialties may find other methods of practicing the invention. However, those methods are deemed to be within the scope of this invention.

Problems solved by technology

For contact lenses made of the conventional hydrogel materials, that level of oxygen permeability is suitable for short-term wear of the contact lenses; however, that level of oxygen permeability may be insufficient to maintain a healthy cornea during long-term wear of contact lenses (e.g., 30 days without removal).

While this class of lens material reduces the corneal edema and hyper-vasculature associated with conventional hydrogel lenses, they can be difficult to produce because the silicone components and the hydrophilic components are incompatible.

These lenses displayed good oxygen permeability, but had poor wettability and mechanical properties.

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