1. Introduction and Overview
Presentation #1: Overview of AstraPro™ Custom Ablation Planning Software
12/7/2018
AstraPro Resource Presentation

2. General Operational Flow
AstraMax
Diagnostic exams (AstraMax, refraction, rigid contact lens fitting, wavefront)
AstraPro
Surgery planning
LaserScan LSX
AstraScan and AstraScan XL Configurations

3. AstraPro: Custom Ablation Planning Software
Data is input from AstraMax which includes:
Shape, pupil sizes, registration data, pachymetry, asphericity(Q), and other proprietary data points
Refractive data is input
New shape is calculated to maintain the eye’s natural prolate asphericity while correcting the refractive error to the best fit elipsoid model
New shape is calculated with respect to the scotopic pupil
AstraPro presentation #2
We take all the diagnostic data from the diskette and place it into the AstraPro software. In addition, we input manifest refraction. Then we take all this information and fit it to the scotopic pupil size. For primary surgical cases, the new ablation dimension is calculated based on the eye’s natural asphericity.
AstraPro Resource Presentation

4. AstraPro Principals: Volume Description
The volume of the ablation is described by the intersection of the existing, detected anterior surface of the cornea and the ideal cornea surface targeting the pre-operative asphericity
The intersection between the measured surface and the ideal surface must be as large as the scotopic pupil seen projected at the anterior surface of the cornea
Ablation volume is determined by the intersection of the best aconic surface, the manifest refraction, and the pupillary diameter.
AstraPro Resource Presentation

5. Required Data
SHAPE
The shape of the cornea must be measured using triangulation methods to derive elevation with very high resolution (<3 microns)(AstraMax)
Highly irregular corneas with significant discontinuities of the cornea shape will require stereo or multi-view devices that can provide accurate data for these type of cases (AstraMax)
More common irregularities may be measured using more common topographers
Shape is a very important basis for determining the custom ablation profile. A refraction by itself does not “see” shape. Steeper corneas of a given refraction require less of an ablation depth than do flatter corneas. If you've performed RK or other types of refractive surgery, you know that for a flatter cornea you have to produce a greater change in shape to affect the change in refraction than with a steeper cornea. So if we consider only refraction, surgery is blind to shape. You can’t base refractive surgery only on refraction.
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6. The Shape of a Sphere Sphere = single radius of curvature
Increase in
effective power
Sphere = single radius of curvature
Snell’s Law calculates an increase in power towards the periphery due to a change in angle of incidence
The characteristic of a spherical surface with gradually increasing effective power toward the periphery is called spherical aberration
We use Snell’s Law to determine the custom shape. Snell's Law simply states that the angle of incidence affects power, so that a ray of light that is perpendicular to a curved surface has a different effective power than if it is ??????? More peripherally. This property is called “spheric aberration.”
AstraPro Resource Presentation

7. Increase in effective power
Spherical Aberration
Increase in effective power
As the pupil becomes larger at night, the larger the effect of viewing through the higher effective power of the peripheral cornea
If the cornea has spherical aberrations, this results in night myopia and decreased contrast sensitivity
Fortunately, the normal human cornea is not spherical. The peripheral cornea gradually flattens so that the rays of light that are incident to the cornea have a much smaller change in effective power. This is why, as our pupil becomes larger at night, we must take into account more of the peripheral cornea producing more spherical aberrations. This results in the patient having more incidences of glare and halos at night.
Photopic (day pupil)
Scotopic (night pupil)
AstraPro Resource Presentation

8. Less increase in effective power
Higher Power = more +
Asphere: Prolate
Less increase in effective power
Not spherical
A “normal” cornea is about 3 D flatter peripherally than centrally
This is the Prolate shape
Now, a normal human cornea becomes flatter by about 3 diopters as you move out peripherally. This is a “prolate shape”.
Photopic (day pupil)
Scotopic (night pupil)
AstraPro Resource Presentation

9. Asphere: Prolate
A normal cornea is prolate and has an average “Q” value of –0.26
Negative means that the shape flattens from the center to the periphery
The normal prolate cornea has a Q value that's negative by about 0.25.
Scotopic (night pupil)
Photopic (day pupil)
AstraPro Resource Presentation

10. Asphere: Oblate A sphere has no asphericity: Q = 0
Asphere surfaces that steepen toward the periphery have + asphericity (Q>0) and are termed Oblate
Myopic refractive surgical treatments increase + asphericity, i.e., moves shape towards Oblate
Exaggerates the effects of spherical aberration, i.e., more night vision problems
The opposite of a prolate cornea is an oblate cornea, where the cornea becomes steeper as you move toward the periphery. This is an exaggerated form of spheric aberration.
AstraPro Resource Presentation

11. Prolate Vs. Oblate (Asphericity)
Oblate (Q > 0)
Prolate
(Q < 0)

12. Examples of Aspheric Values
Asphericity “Q”
Cornea -2
Severe kerataconus -1
Mild kerataconus
-.25
Normal cornea
Sphere
+1.00
8 cut RK
+2.00
16 cut RK
In keratoconus, the cornea is much steeper in the center than it is toward the periphery. So, we exaggerate the Q value and it becomes more minus. When RK was performed, the center of the cornea was flattened so that there was actually a positive increase in Q value. The result was problems with spheric aberration and night vision.
Here are some examples of aspheric values. The degree to which the cornea deviates from or prolate determines the degree of spheric aberration.
AstraPro Resource Presentation

13. Required Data SHAPE SCOTOPIC PUPIL
The projection of the scotopic pupil on the anterior surface of the cornea is measured in dark conditions with an infrared instrument (AstraMax)
Shaping the ablation profile to provide full coverage of the scotopic pupil will minimize aberrations under dimly lit conditions
After shape, the second most important aspect to consider is the scotopic pupil size. We want to make sure that the aspheric shape completely covers the nighttime pupil size.
AstraPro Resource Presentation

14. Required Data
SHAPE
SCOTOPIC PUPIL
MANIFEST REFRACTION
The subjective refraction is the most important parameter for the determination of the ideal aconic surface for the cornea
The third required data point is manifest refraction. An accurate manifest refraction should create the differential between the best fitting aconic surface, or the best aspheric surface, and the new aspheric surface. This is the differential in tissue that's removed beyond taking out the irregularities in the cornea.
AstraPro Resource Presentation

15. AstraMax Data
Anterior Cornea
Posterior Cornea
Spatial Resolved
Refractive Error
The data points of our best manifest refraction are calculated and put into the AstraMax.
Corneal Thickness and
Anterior Chamber Depth
Scotopic Pupil Size
AstraPro Resource Presentation

16. Calculating the Ideal Aconic Surface
The vectorial sum of the refractive properties of the anterior corneal surface and the subjective refraction = the new surface
The new targeted surface will be optimized to respect the cornea’s pre-operative asphericity, i.e., to preserve the natural prolate nature of the cornea
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AstraPro Resource Presentation

17. AstraPro: Summary of Features
Imports Corneal Topography
Optimized Treatment Planning
Advanced Surgical Planning
Safety Features

18. Imports Corneal Topography
Reduces the roughness of the eye
Allows treatment of irregular corneas
Allows treatment of asymmetric corneas

19. Circular Treatments Circular, tissue-saving ablation profiles
Profile centered in pupil
Optimizes optical zone for astigmatic treatments

20. Optimized Treatment Planning
Circular Treatments
Pupil Center Offset
Blend Zone
Ablation Modulation Function (AMF)

21. Circular Vs. Elliptical Treatments
Pupil
Elliptical zone along the minor axis of the astigmatism (too much ablation outside the pupil)
Elliptical zone along the major axis of the astigmatism (does not cover optical zone of pupil)

22. Pupil Center Offset Pupil center offset from the visual axis
Final surface is offset from the pupil center
Saves tissue by not having to increase the optical zone to compensate for the offset

23. Pupil Center Offset Pupil Pupil Center
Area inside pupil not treated when OZ = Pupil
Visual Axis

24. Pupil Center Offset Pupil Center Pupil
Additional treatment causes a much deeper ablation when OZ > Pupil
Visual Axis

25. Pupil Center Offset Visual Pupil Axis Center Optical Zone
Initial Surface
Final Surface
Optical Zone

26. Blend Zone Blend between optical and treatment zones
Gaussian function ensures continuous curve along the target eye surface
Profile is blended to the target eye, not to a flat surface

27. Blend Zone

28. Ablation Modulation Function
Maintains or improve prolate shape
Corrects for laser fluence reduction in periphery
This algorithm may be extensible to the laser platform directly

29. Laser Fluence ReductionB1
Fluence =
Area
Energy B2
The area of B2 is larger than the area of B1, so B2 has less fluence if the energy remains constant.

30. Advanced Surgical Planning
Aspheric Ellipsoid Model
Contact Lens Over-Refraction Method
Target Refraction
Optical and Treatment Zones
Nomogram Adjustment
Target Z-Axis Offset
Effective Refractive Change

31. Aspheric Ellipsoid Model
Initial and final eye surfaces
Parameters: K1, K2, axis, asphericity (Q), defined as the apical keratometry
Corrects for the keratometric index of refraction
Novel algorithm to add spherical refraction to aspherical surfaces

32. Contact Lens Over-Refraction
CLOR method for irregular or asymmetric surfaces
Set of rigid contact lenses
May provide best correction

33. Target Refraction
Allows surgeon to record target refraction separately from spectacle or contact lens refraction
Ideal for mono-vision patients

34. Optical and Treatment Zones
The default OZ is set to the scotopic pupil diameter or 6mm, whichever is larger
The TZ is set to 1mm (SER myopia) or 2.5mm (SER hyperopia) larger than the optical zone.
The surgeon may modify the OZ and TZ within the range 3-9mm

35. Nomogram Adjustment
Persistent Sphere/Cylinder adjustments separately for myopic astigmatism, hyperopic astigmatism, and mixed astigmatism
Sphere/Cylinder adjustment may be modified for individual treatments
Applied to refraction, prior to AMF

36. Target Z-Axis Offset Provides an offset to the Target Z-Axis
Automatically computed by the software
Optimizes treatment plan (saves tissue) for irregular surfaces

37. Effective Refractive Change
Estimated from the corneal topography and apical keratometry
Computed in terms the surgeon can understand, using the spherical approximation of the initial and final surfaces

38. Safety Features
Treatment depth computed normal to the eye surface and compared with pachymetry at all points
Warning messages and restrictions
Patient data (name, gender, eye) provided for visual confirmation
Advanced Visual Display

39. Visual Display
Keratometric axial power map duplicates image from topographer, as a double-check
Preop elevation difference map from best fit asphere of keratometry
Predicted postop elevation difference map from best fit asphere of keratometry
Ablation profile (depth map)

40. AstraPro: Planning Screen
Topography data is displayed
After capturing the patient exam on the AstraMax, the AstraPro planning software will be used to plan the ablation. On the windows based main planning screen, we'll touch the import patient data button.
Patient Data is automatically imported form AstraLink
AstraPro Resource Presentation

41. AstraPro: Planning Screen
Surgical parameters entered
This screen allows us to do iterative planning, surgeons can adjust some of the parameters to see what the postoperative results will look like after the ablation has been performed.
Resultant treatment dimensions
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42. AstraPro Configuration Screen
Here is the pre-operative topography of the ablation profile that we planned just prior to surgery. This is a subtraction.
If we take the preoperative topography and the subtraction, we will get the expected ideal post-operative shape.
AstraPro Resource Presentation

43. AstraPro Main Screen With 3D Rotation and Inspection
The planning screen allows the surgeon an opportunity to change the ablation so it is larger.
Here the surgeon has specified an optical zone that is larger than the scotopic pupil size as his choice, and has also modified the asphericity.
Let's move back so we can see what that difference was from the original plan. You can see the theoretical size of the postoperative ablated zone as well as the new optical zone based upon some additional parameters that the physician chose as modifications.
AstraPro Resource Presentation

44. AstraPro Planning Screen With 3D Rotation and Inspection

45. Summary
The calculations to optimize the new corneal shape targets the natural pre-operative asphericity
Potentially results in:
Decreased spherical aberrations
Improved night vision
Improved contrast sensitivity
The result of all these calculations is that the natural asphericity of the cornea is maintained, which decreases spherical aberrations by removing the irregularities from the cornea. This is done by fitting a best aconic surface to the cornea in order to get better nighttime vision and potentially improved visual acuity, ultimately resulting in satisfied patients and clinical outcomes.
End of Presentation #2 on AstraPro.
AstraPro Resource Presentation