Very high myopic LASIK using new hybrid aspheric profiles

Very high myopic LASIK using new
hybrid aspheric profiles

Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth1,2,3,4

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. Centre Hospitalier National d’Ophtalmologie, (Pr. Laroche) , Paris, France

First Results: Munnerlyn Ablation Profile

• Early ablation profiles often induced:
– Night Vision disturbances
– Decreased contrast sensitivity
• Limited the range of treatable refractions
• PROBLEM: Induction of spherical aberration

Eur J Ophthalmol. 1994 Jan-Mar;4(1):43-51. Night vision after
excimer laser photorefractive keratectomy: haze and halos. O'Brart
DP, Lohmann CP, Fitzke FW, Smith SE, Kerr-Muir MG, Marshall J.
©DZ Reinstein 2009
dzr@londonvisionclinic.com

Ablation Profile Design: Larger Optical Zone
Example: 5-mm Munnerlyn ablation for -6.00 D (1993 Summit Laser)
Topography Wavefront

Z(4,0) (OSA)

1.18 µm

J Refract Corneal Surg. 1994 Mar-Apr;10(2):87-94.
Excimer laser photorefractive keratectomy for myopia:
comparison of 4.00- and 5.00-millimeter ablation zones.
O'Brart DP, Gartry DS, Lohmann CP, Muir MG, Marshall J.

Arch Ophthalmol. 1995 Apr;113(4):438-43. The effects of
ablation diameter on the outcome of excimer laser
photorefractive keratectomy. A prospective, randomized,
double-blind study. O'Brart DP, Corbett MC, Lohmann CP,
Kerr Muir MG, Marshall J.
©DZ Reinstein 2009

Ablation Profile Design: Aspheric Profiles
• Barraquer 1980
– Suggested parabolic keratomileusis

• Seiler 1993 – PRK aspheric profiles
– Less starburst & halos
– Larger effective clear optical zone size

©DZ Reinstein 2009

Why was spherical aberration
increasing?

Optimization: Fluence correction
• Fluence correction: Topography
– Beam reflection compensation
– Beam projection compensation

J Refract Surg 2001;17(5):S584-7.
Influence of corneal curvature on
calculation of ablation patterns
used in photorefractive laser
surgery. Mrochen M, Seiler T.

©DZ Reinstein 2009

Optimization

• Biomechanics

VHF digital ultrasound

©DZ Reinstein 2009

Reinstein et al. Journal of Refractive Surgery
Artemis C12 Display 2000 Jul-Aug;16:414-30

VHF digital ultrasound

Roberts C. The cornea is not a piece of plastic.
JRS 2000; 16:407-413

©DZ Reinstein 2009

Examples of Peripheral Stromal Thickening

Peripheral Stromal
Thickening

Central Flattening

©DZ Reinstein 2009

Corneal Biomechanical Trade-off

• Hyperopic shift induced by
– Central flattening due to peripheral tissue removal

• Myopic shift induced by
Pre-Op
– Epithelial thickening
– Bowing of the back surface
Epithelial thickening
Post-Op

Back surface bowing

©DZ Reinstein 2009

ESCRS 2002, DZ Reinstein: Z4,0-Slider (aka Q-slider)

©DZ Reinstein 2009

Free Lunch?

• Increasing ablation zone diameter
• Adding asphericity

• Increases central
ablation depth
• No “Free Lunch”

©DZ Reinstein 2009

550 µm Pachymetry: Forces Compromise
• Modern aspheric ablation profiles still induce spherical
aberration
• Problem: high myopic corrections may result in NVDs
Attempted Spherical Equivalent vs. Change in Z(4,0) Coefficient
ASA Treatments
0.7

y = -0.059x - 0.0136
0.6
) R² = 0.6444
A
S
O 0.5
,
m
µ
(
t 0.4
n
e
i
c
i
f
f 0.3
e
o
C 0.2
)
0
,
4
(
Z 0.1
n
i
e
g 0.0
n
a
h
C -0.1

-0.2
0.00 -1.00 -2.00 -3.00 -4.00 -5.00 -6.00 -7.00 -8.00 -9.00 -10.00

Attempted Spherical Equivalent (Diopters)

©DZ Reinstein 2009

Wavefront-Guided Treatment
of Spherical Aberration

Correlation of Contrast with Wavefront
Spherical Aberration Contrast Sensitivity
p
900 1.2
800 t 1.1
s
700 a o
r i
t t 1.0
600 n a
o R
C y 0.9
500 t
d i
e v
z i
t
2 400 i i
l s
a n
0.8
m 300 m
r e
µ o S
0.7
200 N
0.6
100
0.5
0 3 cpd 6 cpd 12 cpd 18 cpd
Pre CRS-M Post CRSM-
Control Pre Control Post Control Pre 1.02 1.02 1.03 1.04
Repair Repair
Control Post 1.04 1.01 1.03 1.01
Sph Ab Area 122 276 563 410 Pre CRSM-Repair 0.85 0.84 0.77 0.75
Post CRSM-Repair 1.04 1.02 1.02 1.00

• 27% Gross Reduction
• 53% Net Reduction (cf tolerable level)
• Tolerable level ~0.56 µm @ 6mm

©DZ Reinstein 2009

Pre-Compensate for Spherical Aberration

• “Q-slider”
– (WaveLight)
• Wavefront-guided ablation
– Includes pre-op spherical aberration
– Effect dependent on pre-op spherical aberration

• Our Approach: Include an “artificial” wavefront
– Isolate spherical aberration: Z(4,0) as the only coefficient
– Z(4,0) coefficient proportional to expected induction
– Increase Z(4,0) coefficient: wavefront only 20% effective

©DZ Reinstein 2009

Patient 1, OD

-7.13 D Corrected

6mm OSA 6mm OSA
Coma 0.09 µm Coma 0.04 µm
Sph Ab 0.48 µm Sph Ab 0.42 µm
HO RMS 0.59 µm HO RMS 0.52 µm

©DZ Reinstein 2009

Patient 1, OS

-9.00 D Corrected

6mm OSA 6mm OSA
Coma 0.03 µm Coma 0.05 µm
Sph Ab 0.49 µm Sph Ab 0.55 µm
HO RMS 0.57 µm HO RMS 0.60 µm

©DZ Reinstein 2009

Patient 1, Night Vision

Pre Op Post Op

Rx Treated
OD -6.50 -1.25 x 178
OS -8.25 -1.50 x 17

©DZ Reinstein 2009

Induction of Spherical Aberration

Complaint of NVD post RS1

1

©DZ Reinstein 2009

Limits to SA Pre-Compensation
• Excess spherical aberration pre-compensation can
lead to “central islands”

TMS WASCA (zonal) Epithelium

OD

©DZ Reinstein 2009

CENTRAL ISLANDS:
-5.50 D ablation
Diplopia first week
Slow resolution over 2 weeks

Slides courtesy Gordon Balazsi, MD
©DZ Reinstein 2009

CENTRAL ISLANDS:
-5.00 D ablation

Slides courtesy Gordon Balazsi, MD
©DZ Reinstein 2009

Ablation Depth with SA Pre-Compensation

©DZ Reinstein 2009

New Profile for High Myopia

• Non-linear aspheric ablation profile:
– Increased peripheral ablation (not ↑ z(4,0))
– Reduced induction of spherical aberration
– Free lunch: some myopia corrected due to central
flattening

Extend this concept further to promote central flattening
Ability to correct high myopia without risk of NVDs

Peripheral Stromal
Thickening

Central Flattening

©DZ Reinstein 2009

New Profile: “Free Lunch”
• Over-corrected by +0.50 D compared with theory
• Ablation depth lower than expected
Attempted vs. Achieved Spherical Equivalent
-14

y = 0.9958x - 0.5106
) -13 R² = 0.9291
s
r
e
t
p-12
o
i
D
(
t -11
n
e
l
a
v -10
i
u
q
E -9
l
a
c
i
r
e -8
h
p
S
d -7
e
v
e
i
h -6
c
A
-5
-6 -7 -8 -9 -10 -11 -12 -13 -14


©DZ Reinstein 2009

Ablation Depth for New Profile

©DZ Reinstein 2009

Femtosecond Lasers
• Femtosecond lasers have improved flap thickness
reproducibility (VisuMax SD: 8 µm)
• We can create thinner flaps (VisuMax: 80 µm)
• Thinner flaps extends the range of myopia in LASIK

Pre-release online

©DZ Reinstein 2009

Example RST Planning

Refraction -10.75 D sph

Pachymetry 509 µm

Flap Thickness (VisuMax) 80 µm

Ablation Depth 135 µm

Predicted RST 296 µm

©DZ Reinstein 2009

New Profile for High Myopia

• Patients
– Myopia SEQ -9.51 ± 1.32 D -8.00 up to -14.50 D
– Myopia max merid -10.18 ± 1.48 D -8.00 up to -16.00 D
– Cylinder -1.32 ± 1.10 D up to -6.25 D
– 220 eyes
– 1 year follow up
• Retreatments
– 45% eyes treated as “two-stage”
– Enhancement rate (non two-stage): 35%

©DZ Reinstein 2009

Advantages of Two Stage Procedure
• Increased safety
– Greater RST for primary treatment
– Artemis measured RST to calculate retreatment
– Option to retreat using topography-guided profile
• More accurate result
• Patient has lower expectations

©DZ Reinstein 2009

Topography Guided Retreatment
Pre Post Reduced

Sph Ab 0.48 µm 0.28 µm 41%

HO RMS 0.72 µm 0.57 µm 21%

©DZ Reinstein 2009

MEL80 High Myopia: Accuracy
Attempted vs. Achieved Spherical Equivalent
-14

) y = 1.0726x + 0.8394
s
r
e
t
-13 R² = 0.8759
p
o
i
D
(
t -12
n
e
l
a
v
i -11
u
q
E
l
a
c
i -10
r
e
h
p
S -9
d
e
v
e
i
h -8
c
A

-7
-7 -8 -9 -10 -11 -12 -13 -14

©DZ Reinstein 2009

MEL80 High Myopia: Accuracy
Within ±0.50
71%
D
Within ±1.00
94% Accuracy: Within Range of Intended
D
35% 33%

30%
25%
s 25%
e
y
E 20%
e 15%
g 15% 13%
a
t
n
e 10%
c
r 7%
e
P 5% 3%
0% 1% 1%
0%
-2.00 -1.50 -1.00 -0.50 -0.13 0.14 +0.51 +1.01 +1.51
To - To - To - To - To To To To To
1.51 1.01 0.51 0.14 0.13 +0.50 +1.00 +1.50 +2.00
Accuracy 0% 3% 15% 33% 25% 13% 7% 1% 1%
Accuracy of Spherical Equivalent

©DZ Reinstein 2009

Monocular Efficacy
(excluding eyes not intended plano)

n=176
Efficacy: Monocular UCVA
100% 99% 99% 99%
100% 97%
90%
83%
80%
s
e
y
E 60%
e 47%
g
a
t
n 40%
e 28%
c
r
e
P 20%
11%
1%
0%
20/12.5 20/16 20/20 20/25 20/32 20/40 20/63
Pre BSCVA 1% 28% 83% 100%
Efficacy 11% 47% 90% 97% 99% 99% 99%

Monocular UCVA

©DZ Reinstein 2009

MEL80 High Myopia: Safety – BSCVA
n=220 Safety: Lines Change BSCVA

60%
52%

s 40%
e
y 40%
E
e
g
a
t
n
e 20%
c
r
e
P N=4
6%
2%
0.0% 0.0%
0%
Loss 3 or No Gain 2 or
Loss 2 Loss 1 Gain 1
More Change More
Safety 0.0% 0.0% 2% 40% 52% 6%

Lines Change BSCVA

©DZ Reinstein 2009

Stability
2.00

) 0.00
D
(
t
n
e
l -2.00
a
v
i
u
q
E -4.00
l
a
c
i
r
e -6.00
h
p
S

-8.00

-10.00

-12.00
3 Mo 6 Mo 12 Mo 24 Mo

Pre-op 1 Day 1 Month 3 Months 6 Months 1 Year 2 Years

Mean±SD -9.60±1.39 +0.41±0.82 +0.01±0.82 -0.18±0.86 -0.22±0.91 -0.04±0.91 -0.06±1.07

# eyes 220 199 201 188 158 124 45

©DZ Reinstein 2009

Take Home Message
• Know your spherical aberration induction per dioptre
• Measure pre-op spherical aberration
• Check whether spherical aberration is going to go
beyond the threshold
– Use SA pre-compensation
– Use a 2-stage procedure (wavefront / topography guided
repair if necessary as second treatment)
• Caution with predicted RST
– Reduce potential errors
– Measure pachymetry with high repeatability instrument
– Use high reproducibility flap creation technique
– Always include flap thickness bias
©DZ Reinstein 2009

Thank You

Very high myopic LASIK using new
hybrid aspheric profiles
Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth1,2,3,4

Very high myopic LASIK using new hybrid aspheric profiles

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