centration of hyperopic corneal ablations: corneal vertex vs. pupil center
DESCRIPTION
Centration of Hyperopic Corneal Ablations: Corneal Vertex vs. Pupil CenterTRANSCRIPT
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
©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)
©DZ Reinstein [email protected]
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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Centration: Visual Axis vs Entrance Pupil
Ph
oro
pto
r Len
s
No Angle Kappa
Phoroptor Manifest Refraction Excimer Laser Ablation
Large Angle Kappa
Ab
lation
Pro
file
Ph
oro
pto
r Len
s
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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
©DZ Reinstein [email protected]
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0Eyes (n
)
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
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
-0.4
-0.2
0
0.2
0.4
0.6
0.8
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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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
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