Wavefront Analysis of Flap & Laser-induced aberrations in...

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

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)




• 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.


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



0.790.02-0.0122Vertical Coma


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





• 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





P - valueStd.Error

MeanNVariable

Table 5: Changes in higher order aberrations from pre-op to 1 week post-laser

0.310.030.0322Other terms





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!

Wavefront Analysis of Flap & Laser-induced aberrations in...

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