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WavefrontWavefront Analysis of Flap Analysis of Flap& Laser-induced& Laser-inducedaberrations inaberrations in2-step LASIK2-step LASIK
Ann Laurenzi, O.D.Cole Eye InstituteCleveland Clinic Foundation
Co-AuthorsMaria Regina Chalita, M.D.
Samra Waheed, M.D.Meng Xu, M.S.
Ronald R. Krueger, M.D.
PURPOSE• To identify
aberrations createdin a 2-step LASIKprocedure– Step 1: making the
LASIK flap with nolaser treatment
– Step 2: 1m laterlifting the flap &treating therefractive error witha flying spot laser.
Methods
• Prospective randomized case series
• 11 patients, 22eyes, scheduled for myopicLASIK
• Range: -1.00D to -9.25D sphere with
< 2.75D of astigmatism
• 5 males and 6 females
• Mean age 43.7 years old
MethodsMeasurements: UCVA, MR, BCVA & WF
Schedule: Surgical Treatment:
– Pre-operative ..................Flap Created
– 1 day Post Flap
– 1 week Post Flap
– 1 month Post Flap ..........Flap Lifted & Laser
– 1 day Post Laser
– 1 week Post Laser
– 3 months Post Laser
Methods
• Microkeratomes: MoriaM2 & SKBM
• 22 eyes mean flap
thickness
– 10 eyes SKBM: nasal flap 169 + 27 um
– 12 eyes Moria M2: 142 + 24 um• 6 eyes nasal flap• 6 eyes superior flap
– Randomly selected
randomly selected
Methods• Laser Excimer ablation was performed on
all eyes with the LADARVision 4000 andbased on the one month post flap manifestand cycloplegic refraction.
• Wave front analysis was performed on theLadarWave aberrometer. Analysis wasperformed using a 6.0mm pupil size.
• Statistical analysis: preformed on repeatedmeasures of the variance in the change frompre-op adjusted with Bonferroni correction.(p<0.0125)
RESULTS• Trend towards a slight hyperopic shift was
noted in both sphere of the MR and WFrefraction with Moria M2
• No significant associations between hingeplacement and horizontal and vertical coma
• At 1 week post flap the RMS value of totalHOA and other terms showed a statisticallysignificant increase. At 1 month SA alsoshowed a statistically significant increasefrom pre-op.
• Changes in HOA from pre-op increasedpost-laser at 1w and 3m in Total HOA andSA
0.87169 +/- 270.140.03-4.33-4.3510
SKBM
0.001142 +/- 240.080.52-3.83-4.3512
Moria M2
P-value
Flap ThicknessMean +/- SD
Std.Error
MeanDiff.
1weekpostflap
Pre-op
NMicrokeratome
Table 1 : Effect of type of microkeratome on manifest sphereat 1 week post flap creation
0.73169 +/- 270.170.06-4.72-4.3510
SKBM
0.003142 +/- 240.080.50-3.83-4.3512
Moria M2
P-value
FlapThicknessMean +/- SD
Std.Error
MeanDiff.
1weekpostflap
Pre-op
NMicrokeratome
Table 2 : Effect of type of microkeratome on manifest sphereat 1month post flap creation
Flap Induced Hyperopia(Manifest Refraction)
1 wk
1 mo
RESULTS• Trend towards a slight hyperopic shift was
noted in both sphere of the MR and WFrefraction with Moria M2
• No significant associations between hingeplacement and horizontal and vertical coma
• At 1 week post flap the RMS value of totalHOA and other terms showed a statisticallysignificant increase. At 1 month SA alsoshowed a statistically significant increasefrom pre-op.
• Changes in HOA from pre-op increasedpost-laser at 1w and 3m in Total HOA andSA
Hinge position and Coma
• Vertical Coma: pre-op– To 1 day post-flap (p=0.98)– To 1 wk post-flap (p=0.66)– To 1 mo post-flap (p=0.79)
• Horizontal Coma: pre-op- To 1 day post-flap (p=0.97)- To 1 wk post-flap (p=0.63)- To 1 mo post-flap (p=0.33)
RESULTS• Trend towards a slight hyperopic shift was
noted in both sphere of the MR and WFrefraction with Moria M2
• No significant associations between hingeplacement and horizontal and vertical coma
• At 1 week post flap the RMS value of totalHOA and other terms showed a statisticallysignificant increase. At 1 month SA alsoshowed a statistically significant increasefrom pre-op to post flap creation.
• Changes in HOA from pre-op increasedpost-laser at 1w and 3m in Total HOA andSA
0.0050.010.0522Other terms
0.0330.020.0622Sph. Aberration
0.340.030.0322HorizontalComa
0.900.030.0022Vertical Coma
0.0100.010.0922TotalAberrations
P - valueStd.Error
MeanNVariable
Table 3: Changes in higher order aberrations from pre-op to 1 week post-flap
0.0040.010.0522Other terms
0.0080.020.0722Sph. Aberration
0.270.020.0322HorizontalComa
0.790.02-0.0122Vertical Coma
0.0040.020.0822TotalAberrations
P - valueStd.Error
MeanNVariable
Table 4: Changes in higher order aberrations from pre-op to 1 month post-flap
Flap Induced Aberrations
1 wk
1 mo
RESULTS• Trend towards a slight hyperopic shift was
noted in both sphere of the MR and WFrefraction with Moria M2
• No significant associations between hingeplacement and horizontal and vertical coma
• At 1 week post flap the RMS value of totalHOA and other terms showed a statisticallysignificant increase. At 1 month SA alsoshowed a statistically significant increasefrom pre-op.
• Changes in HOA from pre-op increasedpost-laser at 1w in total HOA, SA &otherterms and 3m total HOA & SA.
0.0090.020.0822Other terms
0.0020.090.3822Sph. Aberration
0.100.030.1122HorizontalComa
0.0130.050.1622Vertical Coma
0.0020.100.4122TotalAberrations
P - valueStd.Error
MeanNVariable
Table 5: Changes in higher order aberrations from pre-op to 1 week post-laser
0.310.030.0322Other terms
0.0050.080.3122Sph. Aberration
0.0480.030.0822HorizontalComa
0.0270.070.1722Vertical Coma
0.0040.090.3322TotalAberrations
P - valueStd.Error
MeanNVariable
Table 6: Changes in higher order aberrations from pre-op to 3 month post laser
Flap to Laser Change in Aberrations
Preop to1 wk laser
Pre-op to3 mo laser
Flap Striae Induced ComaOS Moria Nasal Hinge
repositioned flap 1 week striae
Flap Striae Induced ComaOS Moria Nasal (180)
0.430.43
135135°°0.211 W post lift1 W post lift
220220°°1W post flap1W post flap
135135°°0.49PrePre--opop
AxisComa
Flap Flap StriaeStriaeinferonasallyinferonasallyat ~220 at ~220 °°
Discussion
• Limitations– Sample size was small for analysis of
microkeratome results seperately (10 and 12eyes in each group)
– The two microkeratomes had different targetedflap thickness of 130_m (MoriaM2) and 160_m(SKBM)
Conclusion
• Lasik flap creation induces changes in LOAand HOA ocular aberrations.
• The change in LOA is microkeratomedependent, with the MoriaM2 inducing apredictable hyperopic shift of +0.50D
Conclusion
• HOA increase to a much larger degree postlaser than post flap making a two-stepprocedure unnecessary in conventionalLASIK
• Further investigation of flap-inducedaberrations relative to those inducedfollowing customized ablation will berequired in the future.
Thank YouFor
Your Attention!
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