Methods of altering the refractive index of materials
Methods and devices for altering the power of a lens, such as an intraocular lens, are disclosed. In one method, the lens comprises a single polymer matrix containing crosslinkable pendant groups, wherein the polymer matrix increases in volume when crosslinked. The lens does not contain free monomer. Upon exposure to ultraviolet radiation, crosslinking causes the exposed portion of the lens to increase in volume, causing an increase in the refractive index. In another method, the lens comprises a polymer matrix containing photobleachable chromophores. Upon exposure to ultraviolet radiation, photobleaching causes a decrease in refractive index in the exposed portion without any change in lens thickness. These methods avoid the need to wait for diffusion to occur to change the lens shape and avoid the need for a second exposure to radiation to lock in the changes to the lens.
1. A method of altering the optical power of a lens, comprising:
providing a lens comprising a polymer matrix having photobleachable chromophores; and
exposing a portion of the lens to charged particle radiation, causing photobleaching to occur in the exposed portion of the lens and increasing the refractive index of the exposed portion of the lens, thereby altering the optical power of the lens.
2. The method of claim 1 , wherein the charged particle radiation is provided by an electron beam.
3. The method of claim 1 , wherein the photobleachable chromophores are dispersed within the polymer matrix.
4. The method of claim 1 , wherein the photobleachable chromophores are present as pendant groups on the polymer matrix.
5. The method of claim 1 , wherein at least one photobleachable chromophore comprises a reactive site which can crosslink with a reactive site on the polymer matrix.
6. The method of claim 1 , wherein the photobleachable chromophores comprise at least one of: chromophores containing a malononitrile moiety; stilbene chromophores; and azobenzene chromophores.
7. The method of claim 6 , wherein the malononitrile moiety is selected from the group consisting of Formulas (I)-(II):
8. The method of claim 6 , wherein the stilbene chromophore has a structure of Formula (III):
where R 1 -R 10 are independently selected from hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, —COON, and —NO 2 .
9. The method of claim 6 , wherein the azobenzene chromophore has a structure of Formula (IV):
where R 10 -R 20 are independently selected from hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, —COON, —NO 2 , halogen, amino, and substituted amino.
10. The method of claim 1 , wherein the lens is a contact lens.
11. The method of claim 4 , wherein the polymer matrix does not change in volume when crosslinked.
12. The method of claim 4 , wherein the lens is devoid of free monomers.
13. The method of claim 1 , wherein the photobleachable chromophores in the polymer matrix include a first chromophore and a second chromophore.
14. The method of claim 13 , wherein the first chromophore is sensitive to the radiation and is a photoinitiator or catalyst for bleaching the second chromophore.
15. The method of claim 13 , wherein the second chromophore is not sensitive to the radiation but is sensitive to the first chromophore.
16. The method of claim 13 , wherein the first chromophore is transformed form an inactive state to an active state by the exposure to the radiation.
17. The method of claim 13 , wherein the first chromophore is an aromatic ketone.
18. The method of claim 13 , wherein the first chromophore is present in the lens in an amount from about 0.05 to about 5 wt %.
19. The method of claim 13 , wherein the second chromophore is selected from the group consisting of: C.I. Solvent Blue 101; C.I. Reactive Blue 246; C.I. Pigment Violet 23; C.I. Vat Orange 1; C.I. Vat Brown 1; C.I. Vat Yellow 3; C.I. Vat Blue 6; C.I. Vat Green 1; C.I. Solvent Yellow 18; C.I. Vat Orange 5; C.I. Pigment Green 7; D&C Green No. 6; D&C Red No. 17; D&C Yellow No. 10; C.I. Reactive Black 5; C.I. Reactive Blue 21; C.I. Reactive Orange 78; C.I. Reactive Yellow 15; C.I. Reactive Blue 11; C.I. Reactive Blue 4; C.I. Reactive Red 11; C.I. Reactive Yellow 86; C.I. Reactive Blue 163; and C.I. Reactive Red 180.
20. The method of claim 13 , wherein the second chromophore is present in the lens in an amount of from about 0.5 to about 20 wt %.