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Integration of Aberrometry
and Topography with the
i Trace System
July 2005
Joe S. Wakil, MD Tracey Technologies, LLC
EyeSys Vision, Inc.
Founding Technology
Developers:
Vasyl Molebny, DSc
Kiev, Ukraine
Ioannis Pallikaris, MD
Crete, Greece
Canadian & Swedish Governments
Why Aberroscopy?
Current Laser Technology Permits One to
Go Beyond Correction of Sphere and
Astigmatism
You Can Now Address Your Patient’s Quality
of Vision
High Order Aberrations Define
Quality of Vision
Why Ray Tracing?
Because… the Eye is NOT a Telescope!
Pupil Size: Effects Refraction (ex. Night Myopia)
Refraction is NOT a FIXED Number!
Accommodation: Effects Refraction (Instrument Myopia)
Tear Film: Effects Quality of Vision (Aberrations)
Where are the Sources of
Aberrations?
How do they change with Surgery?
Cornea: Astigmatism (Irreg.), Sph & other HOA
Lens: Astigmatism, Coma & other HOA
The Eye is NOT a Telescope
EYE
TELESCOPE
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Off-Axis design
No magnification
Variable aperture
Variable detector res.
Accommodation
Changing fixation
Brain image
processing
• Nature-made
On-Axis design
High magnification
Fixed aperture
Constant detector res.
No accommodation
Fixed alignment
Digital image
processing
• Man-made
Significant Higher Order Aberrations
Trefoil
Coma
Spherical
Aberration
Aberrometer/Wavefront
Technologies
• Hartmann-Shack Lenslet Array
• Tscherning Aberrometer
• Differential Skiascopy
• Ray Tracing
Features:
-Rapid, point by point, IR measurement no data confusion
-Pupillometry with auto-tracking/capture
-Programmable sampling (256 pts.) in any
pupil up to 8mm
-Open Field Fixation – avoid instrument
myopia and measure Accommodation
-Corneal Topography integration –
able to measure Lens Aberrations
Hartmann Shack
Hartmann Shack
Hartmann-Shack
Wavefront Sensor
H/S Photo of patient with tight eye lid courtesy David Williams
Tscherning
Disadvantages of H-S and
Tscherning
• Measures All Points at Once Data Confusion, Compromised Resolution
• Limited Dynamic Range –
Cannot Measure Highly Irregular Eyes
• Highly Sensitive to Noise –
Slow, Requires Multiple Scans
• Expensive Components –
High Cost to Purchase and Repair
• H-S Measures Reverse Aberrations –
Not Physiologic with Real Vision especially
for High Orders in Accomodation
• Tscherning Needs 2-D Imaging of Retina Additional noise and errors
Differential Skiascopy
Disadvantages of Differential
Skiascopy
• Does NOT Measure Skew Aberrations –
Inaccurate WaveFront especially for Trefoil,
Quadrafoil, etc.
• Measures Multiple Points at Once (slit)
and only in Perpendicular Direction Limited WF measurement (axial bias)
• No Open Field Fixation –
Problem of instrument myopia in young
patients
Total Ocular Aberrations
Corneal
Aberrations
Internal
Optics
Aberrations
Total Ocular
Aberrations
*Measuring Corneal Aberration without Lens
or Total Aberration is of Questionable Value
The iTrace
Principles of Tracey
• Programmable thin beam ray tracing
measuring forward aberrations of the eye
• Rapid sequential measurement of data
points over entire entrance pupil (<50ms)
• Localization of each reflected retinal spot
• Integration of individual retinal spots to
form Point Spread Function (PSF)
• Analysis of PSF for higher order
aberrations and other data formats
Programmable Data Sample Points
Multiplying the Number of Sites
Higher Local Density of Sites
Overlay of Two Sets of Site Configuration
Refractive Error Measurements
Myopia
Hyperopia
Retinal Spot Diagram/Point
Spread Function
Data Displays
Retinal Spot Diagram
Refraction Map
40
30
Y,
µm
20
10
0
-10
-20
-20
-10
0
10
20
X, µm
Ablation Map
Wavefront Map
Tracey’s Key Advantage:
Rapid, point-by-point analysis of
256 data points avoids data confusion
associated with simultaneous data
measurements, therefore, all eyes
(highly irregular) can be measured. All
points in any pupil size (2-8mm) each
with full dynamic range (+/- 15 D).
NO COMPROMISES!
Baylor Clinical Study (100 eyes)
by Doug Koch, MD
+7D
-13D
Validation Studies
Three independent studies of
Tracey vs. Manifest Refraction
• Koch et al - 100 eyes
• Slade et al - 42 eyes
• Schalhorn et al - 106 eyes
Results
• Accuracy to manifest
• Reproducibility
<0.12 D
<0.12 D
The iTrace
Normal Eye
Irregular Eye
UCVA vs BCVA
Post
LASIK
Full Corneal Topography
Full Corneal Topography
Keratoconu
s
Normal
iTrace Measures
Accommodation Mechanism
Very Spherical
Accommodation
Horizontal Cyl
Sphere
Variations in
Mapping
Accommodative
Power in the
Natural
Crystalline Lens
Vertical Cyl
Coma
as
Measured by
iTrace
Crystalens Accommodative Arching
73 Year Old Male
Overall Refraction change is 0.5D but Central
Cylinder 2.5 D adds Depth of Field to
Enhance Accommodative Effect
MultiFocal IOL Analysis with
i Trace
• PSF Analysis
• Modulation Transfer Function (MTF)obust Aberrometer
 Pupil Dependent Analysis
 Multi-Zone Refraction Analysis
• Retinal Spot Diagram
 Conoid of Sturm Dynamic Analysis
• Complete Corneal Topography Analysis
• Separates Corneal from Total Aberrations Resulting in
Lenticular (internal ocular) Aberrations
• Measures Accommodation
Multifocal Acrylic IOL
Alcon ReStor Lens
Monofocal Acrylic IOL
Alcon SA-60
Normal Eye
+0.5 D Hyperope
iTrace Summary
• Robust Aberrometer
 Measures Spatially Resolved Refraction and Aberrations
for ALL eyes – including highly irregular
 Measurement Zone from 2.0 to 8.0 mm (Flexible)
 Multi-Zone Refraction Analysis
 Can do Over-Refraction with Contact Lenses or
Spectacles
 Measures Psuedophakic eyes
• Complete Corneal Topography Analysis
• Separates Corneal from Total Aberrations Resulting in
Lenticular (internal ocular) Aberrations
• Measures Accommodation
• Accurate Pupil Size Measurement
Thank you
for your attention.