Method for modifying the refractive index of ocular tissues
A method for providing vision correction to a patient. The method includes: (a) measuring the degree of vision correction needed by the patient and determining the location and shape of refractive structures that need to be positioned within the cornea to partially correct a patient's vision; (b) directing and focusing femtosecond laser pulses in the blue spectral region within the cornea at an intensity high enough to change the refractive index of the cornea within a focal region, but not high enough to damage the cornea or to affect cornea tissue outside of the focal region; and (c) scanning the laser pulses across a volume of the cornea or the lens to provide the focal region with refractive structures in the cornea or the lens. Again, the refractive structures are characterized by a change in refractive index, and exhibit little or no scattering loss.
1. A method for providing vision correction to a patient, the method comprising:
(a) measuring a degree of vision correction needed by a patient and determining location and shape of refractive structures to be positioned within a cornea of the patient to partially correct the patient's vision;
(b) directing and focusing femtosecond laser pulses in a spectral region between 400 nanometers (nm) to 600 nm within the cornea at an intensity high enough to change a refractive index of the cornea within a focal region, but not high enough to damage the cornea; and
(c) scanning the laser pulses across a volume of the cornea to form the refractive structures in the cornea to partially correct the patient's vision.
2. The method of claim 1 , wherein the refractive index of the formed refractive structure differs from the cornea tissue outside of the focal region by 0.005 to 0.06.
3. The method of claim 1 , further comprising verifying the vision correction provided by the refractive structures.
4. The method of claim 2 , wherein the femtosecond laser pulses have a repetition rate from 10 MHz to 300 MHz, a pulse duration of 30 fs to 200 fs, and an average power from 20 mW to 160 mW.
5. The method of claim 4 , wherein the femtosecond laser pulses have a pulse energy from 0.01 nJ to 10 nJ.
6. The method of claim 4 , wherein the focal region is the form of cylindrical volumes from 0.5 μm to 3 μm in diameter and 3 μm to 10 μm in length.
7. The method of claim 2 , wherein the femtosecond laser pulses have a repetition rate from 10 MHz to 300 MHz, a pulse duration less than or equal to 200 fs, and an average power from 20 mW to 160 mW.
8. The method of claim 7 , wherein the femtosecond laser pulses have a pulse energy from 0.01 nJ to 10 nJ.
9. The method of claim 7 , wherein the focal region is the form of cylindrical volumes from 0.5 μm to 3 μm in diameter and 3 μm to 10 μm in length.
10. The method of claim 1 , wherein the spectral region is from 400 nm to 425 nm.
11. The method of claim 1 , wherein the laser pulses have a pulse energy between 0.1 nJ to 2 nJ.
12. The method of claim 1 , further comprising forming the refractive structure having a structural form of at least one of a lens, a prism, a Bragg grating, a microlens arrays, a zone plate, a Fresnel lenses, and a combination thereof.
13. The method of claim 1 , wherein the laser pulses have a wavelength of 400 nm.
14. The method of claim 1 , wherein the laser pulses have a pulse energy between 0.1 nJ to 10 nJ.
15. The method of claim 1 , wherein the laser pulses have an average power from 20 mW to 160 mW.
16. The method of claim 1 , wherein the focal region is in the form of a cylindrical volume having a diameter between 1.0 μm to 2 μm.
17. The method of claim 1 , wherein the method is performed after insertion of an intraocular lens in cataract surgery, and further comprising forming the refractive structures to correct for aberrations resulting from the cataract surgery or for slight misplacement of the intraocular lens.
18. The method of claim 1 , wherein the method is performed after ocular surgery, and further comprising forming the refractive structures to correct for localized optical wavefront aberrations which exist naturally or which are induced by the ocular surgery.