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
a photosensitive donor lacking photoinitiating groups and responsive to a first selective wavelength of energy for generating primary excited state donor molecules which are not responsive to said first selective wavelength, but are responsive to sequentially applied second selective wavelengths of energy for generating secondary higher energy level excited state donor molecules;
the chromophores having a lowest primary excited state greater than the primary excited state of the photosensitive donor, the secondary higher energy level excited state of the photosensitive donor molecules being greater than the lowest primary excited state of the chromophores; and
exposing a portion of the lens to radiation at the first selective wavelength to generate primary excited state donor molecules; and
exposing the exposed portion of the lens to radiation of the second selective wavelength to generate secondary higher energy level excited state donor molecules, causing photobleaching to occur in the exposed portion of the lens and changing the refractive index of the exposed portion of the lens, thereby altering the optical power of the lens;
wherein the photosensitive donor is selected from the group consisting of Formulas (A)-(E):
wherein each Ar is an aryl or substituted aryl; each R is alkyl; and n reflects the number of double bonds in the conjugated bridge and can be from 1 to 4.
2. The method of claim 1 , wherein the lens is a contact lens.
3. The method of claim 1 , wherein the chromophores are selected from the group consisting of naphthalene sulfonyl chloride, quinolone sulfonyl chloride, and alpha-chloromethyl naphthalene.
4. The method of claim 1 , wherein the first and second wavelengths are different.
5. A method of altering the optical power of a lens, comprising:
providing a lens comprising a polymer matrix containing a first chromophore and a second chromophore; and
exposing a portion of the lens to radiation, causing photobleaching to occur in the exposed portion of the lens and changing the refractive index of the exposed portion of the lens, thereby altering the optical power of the lens;
wherein the first chromophore is sensitive to the radiation and is a photoinitiator or catalyst for bleaching the second chromophore;
wherein the first chromophore is an aromatic ketone; and
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 19; 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.
6. The method of claim 5 , wherein the second chromophore is not sensitive to the radiation but is sensitive to the first chromophore.
7. The method of claim 5 , wherein the first chromophore is transformed from an inactive state to an active state by the exposure to the radiation.
8. The method of claim 5 , wherein the first chromophore is present in an amount of from about 0.05 to about 5 wt %; and wherein the second chromophore is present in an amount of from about 0.5 to about 20 wt %.