utilizing topolyzer vario & oculyzer ii for accurate refractive outcomes
DESCRIPTION
Topography guided lasikTRANSCRIPT
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Utilizing TopolyzerVario & Oculyzer II for accurate refractive outcomes
Michael Mrochen, PhD
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VISION - OPTICS - LIGHTVISION - 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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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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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
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VISION - OPTICS - LIGHTVISION - OPTICS - LIGHT
What is different between WFO and T-CAT?
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Ex500Algorithm
WFO Wavefront Optimized for sphere and cylinder
Manifest Refraction
Optical zone
WFOAblation profile
- Refractive
predictability
- Maintain visual
performance
Ex500Algorithm
T-CAT Topography guided for sphere, cylinder and corneal irregularities
Manifest Refraction
Optical zoneT-CAT
Ablation profile
- Refractive
predictability
- Improve visual
performanceHeight maps from
Topolyzer / Oculyzer
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A limiting factor: the subjective refraction
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
Error of refraction (normal eyes)
60% [43% to 75%] ±0.25
92% [80% to 98%] ±0.5
100% [91% to 100%] ±1.0
Error of refraction (irregular cornea)
25% [18% to 33%] ±0.25
50% [41% to 58%] ±0.5
80% [72% to 86%] ±1.0
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VISION - OPTICS - LIGHTVISION - OPTICS - LIGHT
Accuracy of the TopolyzerVario
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44Edges
Edge Detection
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VISION - OPTICS - LIGHTVISION - OPTICS - LIGHT
Accuracy of the TopolyzerVario
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Eye lashes, lid & nose Corneal irregularities
Pupil detection Corneal surface / tear film
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Degree of light scattering is of clinical relevance
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Accuracy of the Oculyzer II
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VISION - OPTICS - LIGHTVISION - OPTICS - LIGHT
Accuracy of the Oculyzer II
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Segmented measurement Motion compensation
Light scattering
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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
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VISION - OPTICS - LIGHTVISION - OPTICS - LIGHT
A small pocket guide on: What to use when?
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Manifest Refraction
How much can
I trust the Rx?
TopolyzerVarioMeasurement
Oculyzer IIMeasurement
Mires of rings well detected?
Scheimpflugimages well detected?
Yes
Successful Topolyzer or
Oculyzermeasurement?
Noex500
Yes
No
Other treatment options
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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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