Centration of Hyperopic Corneal Ablations: Corneal Vertex vs. Pupil Center

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Centration of Hyperopic Corneal Ablations: Corneal Vertex vs. Pupil Center Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4 1. London Vision Clinic, London, UK 2. St. Thomas’ Hospital - Kings College, London, UK 3. Weill Medical College of Cornell University, New York, USA 4. Center Hospitalier National d’Ophtalmologie, (Pr. Laroche), Paris, France

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Centration of Hyperopic Corneal Ablations: Corneal Vertex vs. Pupil Center

Transcript of Centration of Hyperopic Corneal Ablations: Corneal Vertex vs. Pupil Center

Page 1: Centration of Hyperopic Corneal Ablations: Corneal Vertex vs. Pupil Center

Centration of Hyperopic Corneal Ablations:

Corneal Vertex vs. Pupil Center

Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4

1. London Vision Clinic, London, UK2. St. Thomas’ Hospital - Kings College, London, UK3. Weill Medical College of Cornell University, New York, USA4. Center Hospitalier National d’Ophtalmologie, (Pr. Laroche), Paris, France

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©DZ Reinstein [email protected]

Financial Disclosure

The author acknowledges a financial

interest in Artemis™ VHF digital ultrasound

The author is a consultant for Carl Zeiss

Meditec AG (Jena, Germany)

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Where do you center the ablation?

– On the pupil or on the visual axis?

Small angle kappa

Large angle kappa

0.05 mm @ 180

0.75 mm @ 166

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©DZ Reinstein [email protected]

Centration: Visual Axis vs Entrance Pupil

Ph

oro

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r Len

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No Angle Kappa

Phoroptor Manifest Refraction Excimer Laser Ablation

Large Angle Kappa

Ab

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Purpose of the study

To prove that corneal refractive surgery ablations should be centred on the corneal vertex as opposed to the entrance pupil center

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Study Design – Ideal

Include: Eyes with large angle kappa

Group 2:Corneal Vertex Ablation

Group 1:Pupil Center Ablation

Comparison of outcomes

Not ethical for this hypothesis

• Ideal Design:

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Study Design – Proof by Contradiction

• Assumption: Corneal ablation should be centered on the entrance pupil center

• Study: Center all treatments on the corneal vertex

Vertex = Pupil Center

Group 1: Small angle kappa Group 2: Large angle kappa

Good Outcome Poor Outcome x

Vertex ≠ Pupil Center

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IF: PUPIL CENTER = CORRECT TREATMENT

Small Angle Kappa Large Angle Kappa

Safety Good Worse

Accuracy Good Worse

Contrast Sensitivity Good Worse

Pupil wavefront Good Worse

Corneal wavefront Good Good

Night vision Good Worse

Study Design: Outcome Measures

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Small Angle Kappa Large Angle Kappa

Safety Good Good

Accuracy Good Good

Contrast Sensitivity Good Good

Pupil wavefront Good Worse

Corneal wavefront Good Good

Night vision Good Good

Study Design: Outcome Measures

IF: CORNEAL VERTEX = CORRECT TREATMENT

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Methods: Matched Groups

Pupillary offset

Pupillary offset (mm)

Within 0.25 mm0.17 ± 0.05 mm

More than 0.55 mm0.69 ± 0.10 mm

Small angle kappa Large angle kappa

N (eyes) 30 30

Min hyperopic meridian (D)

+3.85 ± 0.98 D(+2.50 to +5.50D)

+3.87 ± 0.90 D(+2.50 to +5.50D)

BSCVA93% eyes ≥ 20/207% eyes = 20/25

93% eyes ≥ 20/207% eyes = 20/25

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Results

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Results: Centration of the corneal ablation

• Measured on the post-operative front surface corneal elevation map from the Orbscan as the distance between the corneal vertex ( ) and the center of the ablation ( ).

Ablation CentrationCorneal vertex

POST Small Angle Kappa

Large Angle Kappa

Mean (mm) 0.075 ± 0.075 0.062 ± 0.064

Range (mm) 0.00 to 0.30 0.00 to 0.20

p=0.462

The ablation was well centred for both groups

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Results: Surgical Outcomes - Accuracy

Post-operative spherical equivalent: Small angle kappa: 0.38D ± 0.80DLarge angle kappa: 0.48D ± 0.73D

No statistically significant difference (p=0.171)Χ2 contingency table

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Results: Surgical Outcomes - Safety

% of eyes

No statistically significant difference (p=0.315)Χ2 contingency table

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Results: Contrast Sensitivity

***

Small angle kappa Large angle kappa

Statistically significant (p<0.05)*

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Results: Pupil center wavefront - WASCA

-0.6

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RMS (um)

Coma SA

Small angle kappa

Large angle kappa

* p=0.004

Aberrations reported in OSA nomenclatureAll values are in microns and for a 6 mm pupil

Pre Post

Coma 0.18 ± 0.11 0.55 ± 0.29

SA 0.22 ± 0.15 -0.24 ± 0.19

Pre Post

Coma 0.25 ± 0.12 0.87 ± 0.33

SA 0.24 ± 0.13 -0.25 ± 0.22

Small angle kappa Large angle kappa

Change in coma and spherical aberration (SA)

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-0.4-0.3-0.2-0.1

00.10.20.30.4

RMS (um)

Coma SA

Small angle kappa

Large angle kappa

Results: Corneal vertex wavefront

Aberrations reported in OSA nomenclatureAll values are in microns and for a 6 mm pupil

Pre Post

Coma 0.34 ± 0.17 0.69 ± 0.34

SA 0.26 ± 0.08 -0.13 ± 0.21

Pre Post

Coma 0.38 ± 0.19 0.72 ± 0.50

SA 0.20 ± 0.09 -0.19 ± 0.19

Small angle kappa Large angle kappa

Change in coma and spherical aberration (SA) * p>0.05

* p>0.05

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©DZ Reinstein [email protected]

Results: Subjective - Night Vision

POST None Slight MildVisually

SignificantSevere

Small angle kappa

67%

n=20

27%

n=8

7%

n=2

0%

n=0

0%

n=0

Large angle kappa

70%

n=21

23%

n=7

0%

n=0

7%

n=2

0%

n=0

None Slight Mild Visually Significant

Surgical Eyes Visual Effects Simulator (Adam Bogart, Toronto, Canada)

No statistically significant difference (p=0.252) – Χ2 contingency table

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Conclusion

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Ablation

Corneal Vertex Centration

Ablation

Pupil Centred Centration

Conclusion

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Centration of Hyperopic Corneal Ablations:

Corneal Vertex vs. Pupil Center

Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4

1. London Vision Clinic, London, UK2. St. Thomas’ Hospital - Kings College, London, UK3. Weill Medical College of Cornell University, New York, USA4. Center Hospitalier National d’Ophtalmologie, (Pr. Laroche), Paris, France

Thank You