Multi-photon absorption for femtosecond micromachining and refractive index modification of tissues

Patent metadata

Field	Value
Publication number	US-9545340-B1
Application number	US-20713708-A
Country	US
Kind code	B1
Filing date	Sep 9, 2008
Priority date	Jun 26, 2007
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

By adapting femtosecond micromachining approaches developed in hydrogels, we can perform Intra-tissue Refractive Index Shaping (IRIS) in biological tissues. We reduced femtosecond laser pulse energies below the optical breakdown thresholds to create grating patterns that are associated with a change in the refractive index of the tissue. To increase two-photon absorption, we used a two (or more)-photon-absorbing chromophore.

First claim

We claim:

1. A method for micromachining a living or fixed ocular tissue, the method comprising:
(a) applying a multiple-photon-absorbing chromophore to the living or fixed ocular tissue;
(b) providing a laser and emitting laser pulses therefrom at a wavelength in the visible or near-infrared range, a pulse width of between 5 fs and 1 ps, a frequency between 1 MHz and 10 GHz, an average power between 1 mW and 1,000 mW, and an intensity high enough to change the refractive index of a focus spot in the ocular tissue, but not high enough to destroy the ocular tissue;
(c) directing said pulses at the ocular tissue and focusing said pulses to form said focus spot such that said multiple-photon-absorbing chromophore undergoes multiple-photon absorption, wherein a size of the focus spot is between 0.5 μm and 50 μm; and
(d) changing the refractive index of the ocular tissue at locations defined by the focus spot, using the multiple-photon absorption caused by the pulses,
wherein the ocular tissue comprises tissue of a lens or tissue of a cornea.

2. The method of claim 1 , wherein the multiple-photon-absorbing chromophore comprises a two-photon-absorbing chromophore, and wherein, in step (c), the multiple-photon-absorbing chromophore undergoes two-photon absorption.

3. The method of claim 2 , wherein the two-photon-absorbing chromophore comprises sodium flourescein.

4. The method of claim 1 , wherein the ocular tissue comprises tissue of a lens.

5. The method of claim 1 , wherein the ocular tissue comprises tissue of a cornea.

6. The method of claim 1 , wherein the locations defined by the focus spot are selected to form a structure selected from the group consisting of Bragg gratings, microlens arrays, zone plates, and Fresnel lenses.

7. The method of claim 1 , wherein the frequency is between 10 MHz and 500 MHz.

8. The method of claim 1 , wherein the pulse width is between 10 fs and 100 fs.

9. The method of claim 1 , wherein the average power is between 10 mW and 100 mW.

10. The method of claim 9 , wherein the average power is between 50 mW and 60 mW.

11. The method of claim 1 , wherein the laser pulses have a pulse energy between 0.01 nJ and 10 nJ.

12. The method of claim 11 , wherein the laser pulses have a pulse energy between 0.1 nJ and 2 nJ.

13. The method of claim 1 , wherein the size of the focus spot is between 0.5 μm and 10 μm.

14. The method of claim 13 , wherein the size of the focus spot is between 0.5 μm and 2 μm.

15. The method of claim 1 , wherein the focus spot is scanned at a scanning speed between 0.1 μm/s and 10 mm/s.

16. The method of claim 1 , wherein the laser pulses have a wavelength between 600 nm and 1,000 nm.

17. The method of claim 16 , wherein the wavelength is between 700 nm and 900 nm.

18. The method of claim 1 , wherein the laser pulses have a wavelength in the near-infrared range above 1,000 nm.

19. The method of claim 1 , wherein the pulse width is between 10 fs and 100 fs, the frequency is between 10 MHz and 500 MHz, the average power is between 10 mW and 100 mW, and the laser pulses have a pulse energy between 0.1 nJ and 2 nJ.

20. The method of claim 19 , wherein the focus spot is scanned at a scanning speed attaining 1 mm/s.

21. The method of claim 20 , wherein the focus spot is scanned at a scanning speed between 1 mm/s and 10 mm/s.

22. The method of claim 1 , wherein the focus spot is scanned at a scanning speed attaining 1 mm/s.

23. The method of claim 1 , further comprising using a wavefront sensor to detect and measure lower and higher order aberrations along an optical path of a given eye, and calculating a topography and magnitude of refractive index changes required to achieve an aberration correction, and wherein the laser pulses are focused either into the tissue of a lens or tissue of a cornea of the given eye in order to carry out micromachining necessary to induce the required refractive index change.

24. The method of claim 23 , wherein the laser pulses are focused into the tissue of a cornea of the given eye in order to carry out micromachining necessary to induce the required refractive index change.

25. The method of claim 24 , wherein an anesthetic and sodium flourescein are applied to the given eye before carrying out the micromachining, and the laser pulses have a wavelength between 600 nm and 1,000 nm and a pulse width between 10 fs and 100 fs.

26. The method of claim 23 , wherein once the micromachining is complete, a wavefront sensor is used to check the correction of the ocular wavefront.

27. The method of claim 1 , wherein the changing the refractive index of the tissue at locations defined by the focus spot creates corneal fiducial markings for aligning eye trackers during laser refractive surgery.

Assignees

• Knox Wayne H
• Huxlin Krystel R
• Ding Li
• Univ Rochester

Inventors

• Knox Wayne H
• Huxlin Krystel R
• Ding Li

Classifications

• A61F9/00804 Primary

  Refractive treatments · CPC title

• A61F2009/0087

  Lens · CPC title

• A61F9/00827 Primary

  Refractive correction, e.g. lenticle · CPC title

• A61F2009/00872

  Cornea · CPC title

• A61F9/008 Primary

  using laser · CPC title