METHOD AND APPARATUS FOR CALCULATING A LASER SHOT FILE FOR USE IN AN EXCIMER LASER

• US 20090306635A1
• Filed: 02/07/2008
• Published: 12/10/2009
• Est. Priority Date: 08/02/2006
• Status: Abandoned Application

• Current Assignee: Technolas Perfect Vision GMBH (Bausch Health Cos., Inc.)
• Original Assignee: Technolas Perfect Vision GMBH (Bausch Health Cos., Inc.)
• Inventors: Hegels, Ernst
• Application Number:
  US12/375,428
• Publication Number:
  US 20090306635A1
• Time in Patent Office: Days
• US Class Current: 606/5
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 2009/00878 Planning
• CPC Class Codes: A61F 2009/00897 Scanning mechanisms or algorithms
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00804 Refractive treatments
• CPC Class Codes: A61F 9/00812 Inlays; Onlays; Intraocular lenses [IOL]
• CPC Class Codes: A61F 9/00814 Laser features or special beam parameters therefor
• CPC Class Codes: A61F 9/0084 Laser features or special beam parameters therefor
• CPC Class Codes: B23K 26/38 by boring or cutting

Abstract

The invention relates to a method and apparatus for calculating a laser shot file for use in an excimer laser comprising the steps of providing information with respect to a desired ablation profile, calculating the shot density of the desired ablation profile, using a cost function for placing laser shots of the excimer laser on grid positions wherein a threshold value is determined based on the calculated shot density of the desired ablation profile.

Claims

1. A method for calculating a laser shot file for use in an excimer laser preferably for performing a refractive laser treatment of an eye or for producing a customized contact lens or an intraocular lens comprising the steps of providing information with respect to a desired ablation profile and using a dither algorithm, wherein the dither algorithm is adapted to the desired ablation profile by using a dynamic threshold for calculating the laser shot file.

2. The method of claim 1, further comprising the steps of using the dither algorithm for discretizing the desired ablation profile on a given grid and deciding for each grid position whether to place a laser shot of the excimer laser on said grid position.

3. The method of claim 2, wherein the dither algorithm is using a cost function for determining for each grid position whether to place a laser shot of the excimer laser on said grid position.

4. The method of any of the foregoing claims, further comprising the step of calculating a shot density for obtaining the desired ablation profile and wherein said dynamic threshold is defined depending on the calculated shot density of the desired ablation profile.

5. The method of any of the foregoing claims, wherein at least two different threshold values are used depending on the desired ablation profile.

6. The method of claim 5, wherein a first threshold value is used for a desired ablation profile having low shot densities and/or a second threshold value is used for a desired ablation profile having high shot densities, wherein said first threshold value is lower than said second threshold value.

7. The method of claim 6, wherein the first threshold value is a value within a range of 0% to 20% of a maximum shot density of the desired ablation profile and/or the second threshold value is a value within a range of 20% to 80% of the maximum shot density and/or a third threshold value is a value within a range of 80% to 100% of the maximum shot density.

8. The method of any of the foregoing claims, wherein the threshold value TV(x, y) is related to the shot density of the desired ablation profile D(x, y) according to the equation:

TV(x,y)=f(D(x,y)).

9. The method of any of the foregoing claims, wherein the threshold value TV(x, y) is linearly related to the shot density of the desired ablation profile D(x, y) according to the following equation:

TV(x,y)=a D(x,y),

wherein a is a factor within the range of 0<

a≦

1.5, more preferably 0.8≦

a≦

1.1 and most preferably a=1.

10. The method of claim 9, wherein the threshold value is set to a value equal or nearby the value of the shot density.

11. The method of any of the foregoing claims, wherein a grid width of the given grid is determined based on the calculated shot density of the desired ablation profile.

12. The method of any of claims 2 to 111, wherein in the step of deciding whether to place a shot on a given grid position a corresponding decision with regard to grid positions in the neighborhood of the given grid position is taken into account.

13. The method of any of the foregoing claims further comprising the step of dividing a desired ablation profile into at least two ablation sub-profiles, calculating the shot density of each of said ablation sub-profiles, and determining a respective grid width based on the respective calculated shot density of each of the ablation sub-profiles.

14. The method of any of claims 2 to 13 further comprising the step of sorting the calculated placed laser shots.

15. The method of any of the foregoing claims, wherein the excimer laser provides a laser beam at a spot size fixed between 0.5 mm and 3.5 mm in diameter, preferably at a spot size fixed between 1.0 to 2.0 mm in diameter.

16. An apparatus for calculating a laser shot file for use in an excimer laser preferably for performing a refractive laser treatment of an eye or for producing a customized contact lens or an intraocular lens comprising means for providing information with respect to a desired ablation profile and using a dither algorithm, wherein the dither algorithm is adapted to the desired ablation profile by using a dynamic threshold for calculating the laser shot file.

17. The apparatus of claim 16, further comprising when using the dither algorithm means for discretizing the desired ablation profile on a given grid and means for deciding for each grid position whether to place a laser shot of the excimer laser on said grid position.

18. The apparatus of claim 17, wherein the dither algorithm is using a cost function for determining for each grid position whether to place a laser shot of the excimer laser on said grid position.

19. The apparatus of any of claims 16 to 18, further comprising means for calculating a shot density for obtaining the desired ablation profile and wherein said dynamic threshold is defined depending on the calculated shot density of the desired ablation profile.

20. The apparatus of any of claims 16 to 19, further comprising means for selecting at least two different threshold values depending on the desired ablation profile.

21. The apparatus of claim 20, wherein a first threshold value is selected for a desired ablation profile having low shot densities and/or a second threshold value is selected for a desired ablation profile having high shot densities, wherein said first threshold value is lower than said second threshold value.

22. The apparatus of claim 21, wherein the first threshold value is a value within a range of 0% to 20% of a maximum shot density of the desired ablation profile and/or the second threshold value is a value within a range of 20% to 80% of the maximum shot density and/or a third threshold value is a value within a range of 80% to 100% of the maximum shot density.

23. The apparatus of any of claims 16 to 22, further comprising means for determining the threshold value TV(x, y) in relation to the shot density of the desired ablation profile D(x, y) according to the equation:

TV(x,y)=f(D(x,y)).

24. The apparatus of any of claims 16 to 22, further comprising means for determining the threshold value TV(x, y) as a linear relationship to the shot density of the desired ablation profile D(x, y) according to the following equation:

TV(x,y)=a·

D(x,y),

wherein a is a factor within the range of 0<

a≦

1.5, more preferably 0.8≦

a≦

1.1 and most preferably a=1.

25. The apparatus of claim 24, further comprising means for setting the threshold value to a value equal or nearby the value of the shot density.

26. The apparatus of any of claims 16 to 25, further comprising means for determining a grid width of the given grid based on the calculated shot density of the desired ablation profile.

27. The apparatus of any of claims 17 to 26, wherein said means for deciding whether to place a shot on a given grid position is using information regarding a corresponding decision with regard to grid positions in the neighborhood of the given grid position.

28. The apparatus of any of claims 16 to 27 further comprising means for dividing a desired ablation profile into at least two ablation sub-profiles, means for calculating the shot density of each of said ablation sub-profiles, and means for determining a respective grid width based on the respective calculated shot density of each of the ablation sub-profiles.

29. The apparatus of any of claims 17 to 28 further comprising means for sorting the calculated placed laser shots.

30. The apparatus of any of claims 16 to 29, wherein the excimer laser provides a laser beam at a spot size fixed between 0.5 mm and 3.5 mm in diameters preferably at a spot size fixed between 1.0 to 2.0 mm in diameter.