Topography guided LASIK, PRK, Pentacam, Oculyzer, Topolyzer, WaveLight, alcon

1. We focus your ideas
Utilizing TopolyzerVario & Oculyzer II for
IROC Science to Innovation AG
Technoparkstrasse 1
8005 Zürich
Tel: +41 43 500 0850
accurate refractive outcomes
Michael Mrochen, PhD

2. VISION - OPTICS - LIGHT
Content
• What essential data are required by your ex500?
• What is different between WFO and T-CAT?
• A limiting factor: the subjective refraction
• Accuracy of the TopolyzerVario
• Accuracy of the Oculyzer II
• A small pocket guide on: What to use when?
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3. VISION - OPTICS - LIGHT
What essential data are required by
your ex500?
• Ablation profile
– A map of required tissue removal at each point of the
cornea
– It’s based on difference between the pre- and to post-operative
cornea anterior surface
– Derived from either modelled or measured anterior
cornea data
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4. VISION - OPTICS - LIGHT
What essential data are required by
your ex500?
• How to calculate an ablation profile?
– Assume a preoperative cornea shape (R,Q, Cyl,…)
– Calculate the postoperative corneal shape based on the
attempted refractive power change
– Define to optical zone
– Calculate the change in corneal height maps within the
optical zone
– Define a transition zone
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Preoperative
Postoperative
Optical zone

5. WFO Wavefront Optimized for sphere and cylinder
T-CAT Topography guided for sphere, cylinder and corneal irregularities
VISION - OPTICS - LIGHT
What is different between
WFO and T-CAT?
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Ex500
Algorithm
Manifest Refraction
Optical zone
WFO
Ablation profile
- Refractive
predictability
- Maintain visual
performance
Ex500
Algorithm
Manifest Refraction
Optical zone
T-CAT
Ablation profile
- Refractive
predictability
- Improve visual
performance
Height maps from
Topolyzer / Oculyzer

6. Error of refraction (normal eyes)
60% [43% to 75%] ±0.25
92% [80% to 98%] ±0.5
100% [91% to 100%] ±1.0
VISION - OPTICS - LIGHT
A limiting factor:
the subjective refraction
Error of refraction (irregular cornea)
25% [18% to 33%] ±0.25
50% [41% to 58%] ±0.5
80% [72% to 86%] ±1.0
Thomas W. Raasch1, Kenneth B. Schechtman2, Larry J. Davis3, Karla Zadnik1 Repeatability of subjective
refraction in myopic and keratoconic subjects: results ofvector analysis. Ophthal. Physiol. Opt. Vol. 21, No.
5, pp. 376±383, 2001

7. VISION - OPTICS - LIGHT
Accuracy of the TopolyzerVario
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44Edges
Edge
Detection

8. VISION - OPTICS - LIGHT
Accuracy of the TopolyzerVario
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Eye lashes, lid & nose Corneal irregularities
Pupil detection Corneal surface / tear film

9. Degree of light scattering is of clinical relevance
VISION - OPTICS - LIGHT
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Accuracy of the Oculyzer II

10. VISION - OPTICS - LIGHT
Accuracy of the Oculyzer II
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Segmented measurement Motion compensation
Light scattering

11. VISION - OPTICS - LIGHT
Consequences of accuracy
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Uncertainty of topography ~ 2 - 5 microns @ 8 mm
2 micrometer will result in an uncertainty of
approximately 0.14 D for an optical zone of 6.5 mm
2 micrometer will result in an uncertainty of
approximately 0.98 D for an optical zone of 2.5 mm

12. VISION - OPTICS - LIGHT
A small pocket guide on:
What to use when?
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Manifest
Refraction
How much can
I trust the Rx?
TopolyzerVario
Measurement
Oculyzer II
Measurement
Mires of rings
well detected?
Yes
Scheimpflug
images well
detected?
Successful
Topolyzer or
Oculyzer
measurement?
No
ex500
Yes
No
Other treatment
options

13. VISION - OPTICS - LIGHT
Summary
• TopolyzerVario and Oculyzer II are accurate
measurement devices as demonstrated by experimental
measurements and clinical studies.
• Measurements of each device can be affected differently
by the condition of the patient’s eye.
• Raw data checks are required to assure accurate
measurements.
• Consequences can be irregular ablations or poor
refractive predictability
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