Method of manufacturing silicone hydrogel contact lenses having reduced rates of evaporation
A wettable silicone hydrogel contact lens having a low ionoflux and low evaporation is manufactured by curing a silicone hydrogel polymerizable composition in a contact lens mold comprising front and back lens-forming surfaces, where one of the lens-forming surfaces has a higher polarity than the other lens-forming surface.
1. A silicone hydrogel contact lens comprising a polymeric lens body that is the reaction product of a polymerizable composition comprising at least one siloxane monomer and at least one hydrophilic monomer, wherein the silicone hydrogel contact lens has an ionoflux between 1.0×10 −6 mm 2 /min and 0.5×10 −3 mm 2 /min and a) a back surface contact angle of less than 45°, or b) an evaporation rate of less than 15 mg/h when measured at 21° C. to 23° C. at 48-50% RH for 2 to 4 hours, or 3) both a back surface contact angle of less than 45° and an evaporation rate of less than 15 mg/h when measured at 21° C. to 23° C. at 48-50% RH for 2 to 4 hours, wherein the silicone hydrogel contact lens comprises an optic zone that consists essentially of the silicone hydrogel, and wherein the silicone hydrogel contact lens having a front surface contact angle that is at least 10% greater than a back surface contact angle.
2. The silicone hydrogel contact lens of claim 1 , having said back surface contact angle of less than 45°.
3. The silicone hydrogel contact lens of claim 2 , wherein the back surface contact angle is less than 30°.
4. The silicone hydrogel contact lens of claim 1 , having an evaporation rate of less than 15 mg/h when measured at 24° C. at 49-50% RH for 2 to 4 hours.
5. The silicone hydrogel contact lens of claim 4 , wherein the evaporation rate is less than 12 mg/h.
6. The silicone hydrogel contact lens of claim 1 , wherein the ionoflux is less than 0.1×10 −3 mm2/min.
7. The silicone hydrogel contact lens of claim 1 , wherein the at least one hydrophilic monomer is a hydrophilic vinyl-containing monomer.
8. The silicone hydrogel contact lens of claim 7 , where the at least one hydrophilic vinyl-containing monomer is selected from N-vinylacetamide, N-vinyl-N-methylacetamide (VMA), N-vinyl-N-ethylacetamide, N-vinyl-2-pyrrolidone (NVP), N-vinylformamide, N-vinyl-N-ethylformamide, N-vinyl isopropylamide, N-vinylcaprolactam, N-vinyloxycarbonyl-L-alanine, 1,4-butanediol vinyl ether, ethylene glycol vinyl ether, diethylene glycol vinyl ether, a poly(ethylene glycol) vinyl ether, or any combination thereof.
9. The silicone hydrogel contact lens of claim 1 having an EWC of at least 30%.
10. The silicone hydrogel contact lens of claim 9 wherein the EWC is about 40% to about 60%.
11. The silicone hydrogel contact lens of claim 1 having a modulus about 0.3 MPa up to about 0.9 MPa.
12. The silicone hydrogel contact lens of claim 1 having a Dk of at least 80 barrers.
13. The silicone hydrogel contact lens of claim 1 that is sterile and sealed a package.