optimized zernike terms selection in customized treatments for laser corneal refractive surgery

$: Optimized Zernike Terms Selection In Customized Treatments For Laser Corneal Refractive Surgery$
Optimized Zernike Terms SelectionIn Customized Treatments

For Laser Corneal Refractive Surgery6 months experience in state-of-the-art treatments

Maria C. Arbelaez, MD1

Samuel Arba Mosquera, MSc2,3

Camila Vidal, OD1

The authors Arbelaez and Vidal have no proprietary interest in the materials presented hereinSamuel Arba Mosquera is employee at SCHWIND eye-tech-solutions

Part of a Doctoral Thesis in Sciences of Vision

1 Muscat Eye Laser Center (Sultanate of Oman)2 Grupo de Investigación en Cirugía Refractiva y Calidad de Visión (IOBA, Spain)

3 SCHWIND eye-tech-solutions (Germany)Preceptor: Jesús Merayo2

Goals:To evaluate the clinical application of two methods for minimizing the required ablation tissue based upon:- objective minimization of the maximum depth of a customized ablation- objective minimization of the ablation volume of a customized ablationboth based on the Zernike expansion of the wavefront aberration

Materials:- SCHWIND CAM Software Platform (not approved by U.S. Food and Drug Administration)

- SCHWIND ESIRIS Excimer Laser (not approved by U.S. Food and Drug Administration)

- SCHWIND Ocular Wavefront Analyzer (not approved by U.S. Food and Dug Administration)

- SCHWIND Corneal Wavefront Analyzer:- OPTIKON Keratron Scout

- Contrast Sensitivity Tester:- Vision Sciences Research Corporation CST 1800 D

Optimized Zernike Terms Selection in Customized Treatments for Laser Corneal Refractive Surgery


Arbelaez, MD. and colsArbelaez, MD. and cols

Groups:3 groups treated with LASIK technique with 30 eyes each:- Corneal Wavefront group (CW): Full customized correction- Min Depth group (MD): Optimal Zernike terms selection for minimum depth- Min Volume group (MV): Optimal Zernike terms selection for minimum time



min Depth min Vol

Only terms of 3rd or higher order (HOA terms) can be disabled

Only terms with optical blur ≤0.25D can be disabled Only terms with optical blur ≤0.25D can be disabled

For each subset of Zernike terms, Automatic Refraction Balance is used

The subset of Zernike terms that needs minimum depth is selected

The subset of Zernike terms that needs minimum ablation volume is selected

CW MD MV




Metric CW group MD group MV group

Eyes (number) 30 30 30

Age (years)(mean, range)

2418 to 35

2920 to 47

2718 to 47

Gender(Male / Female)

19 / 11 14 / 16 17 / 13

Eye(OD / OS)

16 / 14 17 / 13 12 / 18

Pre-op SEq (D)(mean±stddev, range)

-2.80±1.25-5.50 to -1.00

-3.15±1.57-6.38 to -0.75

-2.90±1.44-6.88 to -0.75

Post-op SEq (D)(mean±stddev, range)

-0.22±0.23-0.75 to +0.38

-0.22±0.23-0.75 to +0.25

-0.26±0.21-0.62 to +0.13

Pre-op Sph (D)(mean±stddev, range)

-2.31±1.39-5.25 to 0.00

-2.76±1.63-6.25 to 0.00

-2.38±1.65-6.50 to 0.00

Post-op Sph (D)(mean±stddev, range)

-0.13±0.26-0.75 to +0.50

-0.14±0.24-0.75 to +0.25

-0.14±0.23-0.50 to +0.25

Pre-op Cyl (D)(mean±stddev, range)

-0.98±0.84-3.75 to 0.00

-0.77±0.54-2.50 to 0.00

-1.05±0.86-4.25 to -0.25

Post-op Cyl (D)(mean±stddev, range)

-0.19±0.19-0.50 to 0.00

-0.16±0.19-0.50 to 0.00

-0.24±0.25-0.75 to 0.00


Refractive OutcomesRefractive Outcomes

Very good refractive outcomes from the three groups:

> 57% in 0.25 D; 100% in 1.00 D > 90% in 0.50 DEq; 100% in 1.00 DEq

60%57%

73%

93%100%

93%100%100%100%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

S.

A.

Mos

quer

a S

chw

ind

ET

S

+- 0,2

5

+- 0,5

+- 1,0

Refractive outcome - Percentage within | Attempted |

CW (30) MV (30)

MD (30)

month (eyes)

60%57%

73%

93%100%

93%100%100%100%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

S.

A.

Mos

quer

a S

chw

ind

ET

S

+- 0,2

5

+- 0,5

+- 1

,0

Refractive outcome - Percentage within | Attempted |

CW (30) MV (30)

MD (30)

month (eyes)

93%90%

93%100% 100% 100%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

S. A

. Mos

quer

a S

chw

ind

ET

S

<=0,

5D<=

1D

Defocus Equivalent - Percentage

CW (30)

MD (30)

MV (30)

month(eyes)

93%90%

93%100% 100% 100%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

S. A

. Mos

quer

a S

chw

ind

ET

S

<=0,

5D<=

1D

Defocus Equivalent - Percentage

CW (30)

MD (30)

MV (30)

month(eyes)

Best results for the MV group, but not statistically significant


PredictabilityPredictability

Very high predictability from the three groups. SEq Cyl


Scatter: Attempted vs. Achieved SEQ 'PREDICTABILITY' 3 x 30 eyes

y = 1,00x - 0,22

R2 = 0,97

y = 0,95x - 0,04

R2 = 0,98

y = 0,99x - 0,21

R2 = 0,98

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7Attempted delta SR equiv. [D]

S.

A.

Mos

quer

a S

chw

ind

ET

S

Achieved [D]

overcorrected

undercorrected

Scatter: Attempted vs. Achieved SEQ 'PREDICTABILITY' 3 x 30 eyes

y = 1,00x - 0,22

R2 = 0,97

y = 0,95x - 0,04

R2 = 0,98

y = 0,99x - 0,21

R2 = 0,98

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7Attempted delta SR equiv. [D]

S.

A.

Mos

quer

a S

chw

ind

ET

S

Achieved [D]

overcorrected

undercorrected

Scatter: Attempted change in CYL vs. SIRC 3 x 30 eyes

y = 0,88x + 0,01

R2 = 0,94

y = 0,94x - 0,01

R2 = 0,91

y = 0,95x - 0,10

R2 = 0,92

0

1

2

3

4

0 1 2 3 4Attempted Cyl [D]

S.

A.

Mos

quer

a S

chw

ind

ET

S

Achieved [D]

overcorrected

undercorrected

Scatter: Attempted change in CYL vs. SIRC 3 x 30 eyes

y = 0,88x + 0,01

R2 = 0,94

y = 0,94x - 0,01

R2 = 0,91

y = 0,95x - 0,10

R2 = 0,92

0

1

2

3

4

0 1 2 3 4Attempted Cyl [D]

S.

A.

Mos

quer

a S

chw

ind

ET

S

Achieved [D]

overcorrected

undercorrected


Stability & EfficacyStability & Efficacy

Very stable results from the three groups since the first month follow up

Results for the MD and MV groups better than for CW group,statistically significant (p < 0.01)

Achieved Correction SEQ over Time 'STABILITY'

-3,15

-2,90

-0,24-0,21

-2,80

-0,24-0,21

-0,28-0,23

303030-3,50

-3,00

-2,50

-2,00

-1,50

-1,00

-0,50

0,00

pre op 1 m 3 m

S. A

. Mo

squ

era

Sch

win

d E

TS

Achieved Correction SEQ over Time 'STABILITY'

-3,15

-2,90

-0,24-0,21

-2,80

-0,24-0,21

-0,28-0,23

303030-3,50

-3,00

-2,50

-2,00

-1,50

-1,00

-0,50

0,00

pre op 1 m 3 m

S. A

. Mo

squ

era

Sch

win

d E

TS

17%

37%37%

70%

63%63%

13%

0%

10%

20%

30%

40%

50%

60%

70%

S. A

. Mos

quer

a S

chw

ind

ET

S

UCVA - Percentage 'EFFICACY'

CW (30)

MD (30)

MV (30)

month(eyes)

17%

37%37%

70%

63%63%

13%

0%

10%

20%

30%

40%

50%

60%

70%

S. A

. Mos

quer

a S

chw

ind

ET

S

UCVA - Percentage 'EFFICACY'

CW (30)

MD (30)

MV (30)

month(eyes)

Very good UCVA postoperative from the three groups

> 87% UCVA 20/20 or better


SafetySafety

Between 34% and 47% of the treatmentsgained at least 1 line of BSCVANo single eye lost even 1 line of BSCVA


Between 30% and 40% of the treatments with post-op UCVA were better than pre-op BSCVA

10%

50%

70%

60%

40%

23%

33%

7%7%

0%

10%

20%

30%

40%

50%

60%

70%

S. A

. Mos

quer

a S

chw

ind

ET

S

lost

>=

2

lost

1

unchan

ged

gained

1

gained

>=

2

Change in UCVA vs. preOP BSCVA - Percentage

CW (30)

MD (30)

MV (30)

month(eyes) 10%

50%

70%

60%

40%

23%

33%

7%7%

0%

10%

20%

30%

40%

50%

60%

70%

S. A

. Mos

quer

a S

chw

ind

ET

S

lost

>=

2

lost

1

unchan

ged

gained

1

gained

>=

2

Change in UCVA vs. preOP BSCVA - Percentage

CW (30)

MD (30)

MV (30)

month(eyes)

60%

66%

53%

40%

27%

40%

7%7%

0%

10%

20%

30%

40%

50%

60%

70%

S. A

. Mos

quer

a S

chw

ind

ET

S

lost

>=

2

lost

1

unchan

ged

gained

1

gained

>=

2

Change in BSCVA - Percentage 'SAFETY'

CW (30)

MD (30)

MV (30)

month(eyes)

60%

66%

53%

40%

27%

40%

7%7%

0%

10%

20%

30%

40%

50%

60%

70%

S. A

. Mos

quer

a S

chw

ind

ET

S

lost

>=

2

lost

1

unchan

ged

gained

1

gained

>=

2

Change in BSCVA - Percentage 'SAFETY'

CW (30)

MD (30)

MV (30)

month(eyes)


Contrast SensitivityContrast Sensitivity

Excellent improvement in postoperative contrast sensitivity for all three groups


Contrast Sensitivity Mesopic

0,68

1,32

1,821,76

0,83

1,46

1,941,83

0,84

1,38

1,98

1,81

0,92

1,42

1,98

1,85

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

2,00

2,20

A (3cpd) B (6cpd) C (12cpd) D (18cpd)

S.

A.

Mos

quer

a S

chw

ind

ET

S

pre op (90)

CW (30)

MD (30)

MV (30)

month

Spatial Frequency [cycles/degree]

Contrast Sensitivity Mesopic

0,68

1,32

1,821,76

0,83

1,46

1,941,83

0,84

1,38

1,98

1,81

0,92

1,42

1,98

1,85

0,40

0,60

0,80

1,00

1,20

1,40

1,60

1,80

2,00

2,20

A (3cpd) B (6cpd) C (12cpd) D (18cpd)

S.

A.

Mos

quer

a S

chw

ind

ET

S

pre op (90)

CW (30)

MD (30)

MV (30)

month

Spatial Frequency [cycles/degree]


ComparisonComparison

MD group saved -4 µm depth in averageMV group saved -3 µm depth in average

MD group saved -3 s time in averageMV group saved -4 s time in average

CW MD Diff

Avg. Ablation Depth (µm)

46 ± 32 42 ± 31 -4 ± 2

Ablation Depth range (µm)

24 – 103 19 – 98 -11 – -1

Avg. Ablation Time (s)

38 ± 20 35 ± 20 -3 ± 1

Ablation Time range (s)

17 – 76 15 – 71 -8 – 0

min Depth < Ab-Free (%)

--- 43% (13) ---

CW MV Diff

Avg. Ablation Depth (µm)

46 ± 32 43 ± 31 -3 ± 2

Ablation Depth range (µm)

32 – 88 27 – 83 -9 – 0

Avg. Ablation Time (s)

38 ± 20 34 ± 20 -4 ± 1

Ablation Time range (s)

21 – 86 17 – 73 -13 – 0

min Vol < Ab-Free (%)

--- 40% (12) ---


SummarySummary

Avg. Diff. (µm)

Avg. Diff. (%)

Max. Diff. (µm)

Max. Diff. (%)

min Depth correction

-4 ± 2 -8% -11 -23%

min Vol correction

-3 ± 2 -5% -9 -20%

MD group saved -4 µm depth in averageMV group saved -3 µm depth in average

MD group saved -3 s time in averageMV group saved -4 s time in average

Avg. Diff. (s)

Avg. Diff. (%)

Max. Diff. (s)

Max. Diff. (%)

min Depth correction

-3 ± 1 -7% -8 -24%

min Vol correction

-4 ± 1 -10% -13 -25%

Ablation depth

y = 1,00x

R2 = 1,00

y = 0,97x - 2,32

R2 = 0,99

y = 0,94x + 0,71

R2 = 0,94

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Ablation depth for full customised correction (µm)

Ab

lati

on

dep

th f

or

op

tim

al Z

ern

ike

term

s se

lect

ion

(µ

m)

CorWave

MinDepth

MinVol

Linear (CorWave)

Linear (MinDepth)

Linear (MinVol)

Ablation time

y = 1,00x

R2 = 1,00

y = 0,96x - 2,19

R2 = 0,99

y = 0,89x + 1,50

R2 = 0,96

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90

Ablation time for full customised correction (µm)

Ab

lati

on

tim

e fo

r o

pti

mal

Zer

nik

e te

rms

sele

ctio

n (

µm

)

CorWave

MinDepth

MinVol

Linear (CorWave)

Linear (MinDepth)

Linear (MinVol)


Conclusions:

- The three groups compared here (CW, MD and MV) are Predictable, Safe, Stable and Accurate

- The two minimization techniques compared here can be used to reduce the depth and time needed for the ablation

- Depth and time were effectively reduced by up to a maximum of 25%, and by 8% in average

- The performed ablations reduced in depth and time did not affect negatively the clinical outcomes postoperatively

- The two minimization techniques compared here yielded results equivalent to those of the full customization group

Conclusions:

- The three groups compared here (CW, MD and MV) are Predictable, Safe, Stable and Accurate

- The two minimization techniques compared here can be used to reduce the depth and time needed for the ablation

- Depth and time were effectively reduced by up to a maximum of 25%, and by 8% in average

- The performed ablations reduced in depth and time did not affect negatively the clinical outcomes postoperatively

- The two minimization techniques compared here yielded results equivalent to those of the full customization group






Conclusions II: What I would choose for minimizationConclusions II: What I would choose for minimization

CW MD MV

Minimization principle --- Minimum depthMinimum volumeMinimum time

When to be usedIn very high

aberrated eyesAt risk of

keratectasiaWhen treatment time is very long

Typical case

Low refractive corrections, predominant aberrations

Customized myopias

Customized hyperopias

Typical savings ----4 µm-3 s

-3 µm-4 s

Maximum savings ----10 µm

-8 s-9 µm-13 s


optimized zernike terms selection in customized treatments for laser corneal refractive surgery

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