Utilizing topolyzer vario & oculyzer ii for accurate refractive outcomes

$Page 1: Utilizing topolyzer vario & oculyzer ii for accurate refractive outcomes$
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Utilizing TopolyzerVario & Oculyzer II for accurate refractive outcomes

Michael Mrochen, PhD

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

3


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


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


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


Accuracy of the TopolyzerVario

7

44Edges

Edge Detection


Accuracy of the TopolyzerVario

8

Eye lashes, lid & nose Corneal irregularities

Pupil detection Corneal surface / tear film


Degree of light scattering is of clinical relevance

9

Accuracy of the Oculyzer II


Accuracy of the Oculyzer II

10

Segmented measurement Motion compensation

Light scattering


Consequences of accuracy

11

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


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


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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Healthcare

Utilizing topolyzer vario & oculyzer ii for accurate refractive outcomes