corneal changes following lasik and enhancement with
TRANSCRIPT
Corneal Changes FollowingLASIK and Enhancement with
Microkeratome and FemtosecondLaser Flaps
Jerome C. Ramos-Esteban, MDCole Eye InstituteCleveland Clinic
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Commercial Disclosures
• Jerome C. Ramos-Esteban, MD (none)• Ronald R. Krueger, MD (IntraLase)• Maria Regina Chalita, MD, PhD (none)• Daniel Pierre, MSIV (none)
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Purpose
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Purpose
• To determine the thickness of both LASIK flaps andresidual stromal bed at the time of primary LASIK andLASIK enhancement
• To compare differences in these two parameters according to ablation type
• To determine longitudinal changes in these two parameters between Microkeratome and femtosecond laser procedures
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Methods
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98 patientsn=196 eyes
Microkeratomen=79 eyes
FemtosecondN=117 eyes
Primary LASIK treatment
Myopia n=91Hyperopia=26
Myopia n=59Hyperopia=20
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MethodsPrimary procedures:
- Microkeratome (Moria M2, 110 um head)- Femtosecond (IntraLase 15 and 30 kHz, 110 um flap)
Laser Platform:- Alcon LadarWave 4000
• Preoperative and intraoperative Ultrasound Pachymetry 50 HZ (Sonogage) probe
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Measurements
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Measurements
Primary Procedures
- Central Corneal Thickness- Pre-ablation Stromal Thickness- Post-ablation Stromal Thickness
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Measurements
Enhancement Procedures
- Central Corneal Thickness- Pre-enhancement Stromal Thickness- Post-ablation Stromal Thickness
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Calculations
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Primary Procedures
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Central Corneal Thickness(CCT)
(CCT)
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Primary Flap Thickness(PFT)
PFT = CCT - PAST
Preablation Stromal Thickness(PAST)
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Calculated Primary Post-Ablation Depth(CPPAD)
CPPAD = PAST - TLAD
Theoretical Laser Ablation Depth(TLAD)
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Measured Ablation Depth(MAD)
MAD = PAST - POST
Post-Ablation Stromal Thickness(POST)
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LASIK Enhancements
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Enhancement Central Corneal Thickness(ECCT)
(ECCT)
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Enhancement Flap Thickness(EFT)
EFT = ECCT - PEST
Pre-enhancement Stromal Thickness(PEST)
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Calculated Enhancement Post-Ablation Depth(CEPAD)
CEPAD = PEST - TLAD
Theoretical Laser Ablation Depth(TLAD)
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Measured Enhancement Ablation Depth(MEAD)
MEAD = PEST - POST
Post-Ablation Stromal Thickness(POST)
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Statistical Analysis
• Paired t-test was used to assess differences inthickness between:
- Primary & Enhancement flaps- Calculated & pre-enhacement stromal thickness- Calculated & Measured ablation depth
• A p value < 0.05 was considered statistically significant
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Results
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Microkeratome
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Microkeratome Flap Thickness
0.94119.8120Hyperopia
<0.0001141.8114.9Myopia
p valueEFPPFTMean
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Microkeratome Residual Stromal Bed Thickness
<0.0001411.5366Hyperopia
<0.0001346.6364.1Myopia
p valuePESTCPPADMean
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Femtosecond
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Femtosecond: Flap Thickness
0.07118.6126Hyperopia
0.003141134.9Myopia
p valueEFTPFTMean
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Femtosecond: Residual Stromal Bed Thickness
<0.0001421.2376.32Hyperopia
<0.0001331.8351.2Myopia
p valuePESTCPPADMean
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Femtosecond Primary TreatmentDifference in Ablation Depth
<0.0011954Hyperopia
<0.00110285Myopia
p valueMADTLADMean
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Femtosecond EnhancementDifference in Ablation Depth
<0.001721Hyperopia
<0.0011015Myopia
p valueMEADETLADMean
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Primary LASIK vs. Enhancements
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Flap Thickness DifferencePrimary LASIK vs. Enhancement
0.07- 7.420.94- 0.25Hyperopia
0.003+ 6.1<0.001+ 26.3Myopia
p valueFemtosecondp valueMicrokeratome
FT = EFT - PFT
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Stromal Thickness DifferencePrimary LASIK vs. Enhancement
<0.001+ 44.8<0.001+ 45.6Hyperopia
<0.001- 19.4<0.001- 17.97Myopia
pvalue
Femtosecondp valueMicrokeratome
ST = PEST - CPPAD
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Conclusions
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Microkeratome vs. Femtosecond
Myopic Ablations
• PFT thinner due to underestimation of pre-ablation stromal bed
• Calculated post ablation depth > pre-enhancement stromal bed
Substraction methods are very sensitive to tissue hydration
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Microkeratome vs. Femtosecond
Myopic Ablations
• PFT femtosecond flaps > microkeratome flaps
Possible fluid displacement during flap creation
• Difference Femtosecond & microkeratome EFT not significant
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Microkeratome vs. Femtosecond
Hyperopic Ablations
• No statistically significant differences between PFT and EFT
• Pre-enhancement stromal bed > calculated post ablation depth
Lamellar tension reduction from more peripheral ablation
may lead to increased baseline tissue hydration
Thank you