Oxygen permeable contact lens structures for thick payloads
A variable geometry contact lens structure having a thickness t sufficient to carry an active payload is constructed using layers of materials with high oxygen transmissibility and low oxygen transmissibility. The low transmissibility layer provide mechanical support for the active payload, and the high transmissibility layers provide adequate oxygen transmission to the cornea of the user's eye. The ratio of the thicknesses of the two layers changes abruptly at the boundaries between the payload and non-payload regions of the structure. For example, at a boundary of the payload region, a ratio of thicknesses of the high transmissibility layer t1 to thickness of the low transmissibility layer t2, R=t1/t2, changes by at least 2:1 over a lateral distance of not more than t.
1. A contact lens structure having a maximum thickness t, comprising:
in an optical zone of the contact lens:
a first layer characterized by an oxygen transmissibility Dk1 that would be high enough to provide sufficient oxygen to the cornea if the first layer had a thickness t1=t;
a second layer that provides mechanical support for a payload, the second layer characterized by an oxygen transmissibility Dk2 that would not be high enough to provide sufficient oxygen to the cornea if the second layer had a thickness t2=t;
a payload region disposed between the first and second layers, the payload region configured to contain the payload; and
where, at a boundary of the payload region, a ratio of thicknesses of the first layer to the second layer, R=t1/t2, changes by at least 2:1 over a lateral distance of not more than t.
2. The contact lens structure of claim 1 , where the payload includes active electronics.
3. The contact lens structure of claim 1 , where the payload includes a femtoprojector.
4. The contact lens structure of claim 1 where, in the optical zone, the contact lens structure comprises a plurality of payload regions each configured to contain a payload.
5. The contact lens structure of claim 4 , where the payload regions are disjoint and regions between payload regions have ratios R of thicknesses of the first layer to the second layer that are at least 2× greater than the ratios R within the payload regions.
6. The contact lens structure of claim 1 , where the oxygen transmissibility Dk1 of the first layer is at least 100.
7. The contact lens structure of claim 1 , where the first layer is a silicone layer.
8. The contact lens structure of claim 1 , where the oxygen transmissibility Dk2 of the second layer is not more than 100.
9. The contact lens structure of claim 1 , where the second layer is a rigid gas permeable layer.
10. The contact lens structure of claim 1 , where the second layer is a fluorinated silicone layer.
11. The contact lens structure of claim 1 , where the first layer is an outer layer of the contact lens structure.
12. The contact lens structure of claim 1 , where the second layer is an inner layer of the contact lens structure.
13. The contact lens structure of claim 1 , where the contact lens structure is a scleral contact lens structure.
14. The contact lens structure of claim 1 where:
in the optical zone, the contact lens structure comprises one or more payload regions; and
outside the payload region(s), the thickness t1 of the first layer is monotonically thinner as a function of radius r from a center of the contact lens structure.
15. The contact lens structure of claim 1 where:
in the optical zone, the contact lens structure comprises one or more payload regions; and
outside the payload region(s), the thickness t2 of the second layer is constant.
16. The contact lens structure of claim 1 where:
in the optical zone, the contact lens structure comprises one or more payload regions; and
outside the payload region(s), the thickness t2 of the second layer is monotonically thinner as a function of radius r from a center of the contact lens structure.
17. The contact lens structure of claim 1 where:
in the optical zone, the contact lens structure comprises one or more payload regions; and
outside the payload region(s), the second layer has a spoke structure to provide mechanical support for the payload region(s).
18. The contact lens structure of claim 1 where, in the optical zone, the ratio R varies as a function of an angle θ measured from a center of the contact lens structure.
19. The contact lens structure of claim 1 where, in the optical zone, the ratio R has N-fold symmetry with respect to an angle θ measured from a center of the contact lens structure.
20. The contact lens structure of claim 1 wherein the first and second layers comprise solid materials.