PowerPoint-Pr

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ICT Intraoperative Corneal Topography for
image registration purposes S.Schründer
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Model eye
6mm optical zone
8mm corneal radius
6mm pupil, 4mm below apex
5mm to rotation axis
12mm radius bulbus
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Tilted eye
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Motivation
Treatment
Diagnosis
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Solution
Registration in 3d space
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Requirement
3d objects
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Height map pre ablation
Difference to 8.4mm sphere Range 100µm
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Height map post ablation
Difference to 8.7mm sphere Range 100µm
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Fine registration Iterative Closest Point
Find corresponding 3d points (via Hough
tables) Minimize their distance

• Distance Minimization
• Levenberg-Marquardt
• for fast convergence
• Simmulated annealing
• to overcome local minima

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Registration points area
Detected flap edge
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Difference map after registration
7.5mm circle Range 105µm
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Line scans
Dimensions in mm
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3d Flap thickness
9.5mm circle Range 290µm
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Line scans
Dimensions in mm
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Next steps
Rigid incorporation into a laser system
Extended clinical trials
Stand alone device
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Centered cornea
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0.5mm lateral shift
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Corresponding tilt
0.22mm decentration
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Linear function
8mm corneal radius, 4mm apex/pupil, 13mm
apex/rotation axis
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Coworkers at BioShape
Andreas Dankert Hendrik Fuchs Saso Spasovski
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Thank you. bioshape.com