Method for modifying the refractive index of ocular tissues

Abstract

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.

We claim: 
     
         1 . A method for providing vision correction to a patient, the method comprising:
 (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 local 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.   
     
     
         2 . The method of  claim 1 , wherein the refractive index of the 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 local region is the form of cylindrical volumes from about 0.5 μm to 3 μm in diameter and 3 μm to 10 μm in length. 
     
     
         7 . A method for forming a refractive structure in a living eye, comprising:
 directing and focusing a plurality of femtosecond laser pulses in a spectral region between about 350 nanometers (nm) to about 600 nm within a defined focal region in the cornea or lens of the living eye,   wherein the laser pulses have a repetition rate from 10 MHz to 300 MHz, a pulse duration of 30 fs to 200 fs, an average power from 20 mW to 160 mW, and a pulse energy from 0.01 nJ to 10 nJ;   further wherein the defined focal region is in the form of a cylindrical volume having a diameter between about 1.0 μm to 2 μm and a length between about 3 μm to 6 μm; and   forming a refractive structure in the focal region of the cornea or the lens, further comprising creating a difference in the refractive index of the refractive structure from that outside of the focal region by between about 0.005 to 0.06 without photo disrupting cornea or lens tissue outside of the focal region.   
     
     
         8 . The method of  claim 7 , wherein the spectral region is between about 375 nm to about 425 nm. 
     
     
         9 . The method of  claim 7 , wherein the spectral region is between about 350 nm to about 400 nm. 
     
     
         10 . The method of  claim 7 , wherein the laser pulses have a wavelength of about 400 nm. 
     
     
         11 . The method of  claim 7 , wherein the pulse energy is between about 0.1 nJ to 2 nJ. 
     
     
         12 . The method of  claim 7 , 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.