Evaluation of the Intralase Femtosecond Laser Efficiency in

LASIK Flap Creation

Mounir A. Khalifa, MD Michael Rizman, MD.

Waleed Allam, MD

No financial interest for all authors

• This study aimed at evaluation of the visual and refractive outcomes of wavefront-guided LASIK using the IntraLase femtosecond laser for flap creation.

• The study was conducted at Tufts University School of Medicine, Boston, Massachusetts, USA and included 117 eyes of 63 patients with myopia with or without astigmatism.

Preoperative statistical analysis

Table 1: Patients’ age, preoperative refraction, and visual acuity data.

Minimum Maximum Mean Std. Deviation

Age 22 57 35.90 8.718

LogMAR UCVA 0.40 1.69 1.2503 0.31339

LogMAR BCVA 0.00 0.00 0.00 0.00

Manifest Sphere -8.25 -0.50 -3.9509 1.79206

Manifest Cylinder -2.00 0.00 -0.4081 0.45675

MRSE -8.500 -1.00 -4.15278 1.806218

Preoperative statistical analysis

Table 2: Preoperative topography, pachymetry, and aberrations data.

Minimum Maximum Mean Std. Deviation

Mean K-Reading 40.15 48.40 43.9718 1.61819

Pachymetry 500 633 556.01 31.359

Total rms 0.14 0.81 0.3633 0.13198

Coma 0.02 0.50 0.1909 0.11748

Trefoil 0.00 0.50 0.1478 0.08391

Sph. aberrations -0.38 0.67 0.1338 0.16629

Intraoperative findings

• Achieved flap thickness and diameter:Table 3: Achieved flap thickness and diameter.

Minimum Maximum Mean Std. Deviation

Flap Thickness 91 144 116.48 12.215

Flap Diameter 8.7 9.1 8.956 0.1196

Intraoperative findings

• Pearson simple linear correlation coefficients:

Table 4: Pearson correlation, flap thickness vs mean k-reading.

Flap Thickness Mean K-Reading

Flap Thickness

Pearson Correlation 1 0.017

Sig. (2-tailed) . *0.855

N 116 116

Mean K-Reading

Pearson Correlation 0.017 1

Sig. (2-tailed) *0.855 .

N 116 117

*P=0.855>0.05

No correlation between flap thickness and K-reading

Intraoperative findings

• Pearson simple linear correlation coefficients:

Table 5: Pearson correlation, flap thickness vs pachymetry.

Flap Thickness Pachymetry

Flap Thickness

Pearson Correlation 1 -0.016

Sig. (2-tailed) . *0.866

N 116 116

Pachymetry

Pearson Correlation -0.016 1

Sig. (2-tailed) *0.866 .

N 116 117

*P=0.866>0.05

No correlation between flap thickness and preoperative corneal thickness

Intraoperative findings

• Pearson simple linear correlation coefficients:

Table 6: Pearson correlation, flap diameter vs mean k-reading.

Flap Diameter Mean K-Reading

Flap Diameter

Pearson Correlation 1 -0.048

Sig. (2-tailed) . *0.610

N 116 116

Mean K-Reading

Pearson Correlation -0.048 1

Sig. (2-tailed) *0.610 .

N 116 117

*P=0.610>0.05

No correlation between flap diameter and K-reading

Intraoperative complications

7.8% intraoperative complication rate.

Early postoperative findings

• 114 eyes, out of 117, were available for postoperative follow-up.

• At the first postoperative day, the mean LogMAR UCVA was 0.03 ± 0.11 (mean around 20/22).

• At the first postoperative day, the peripheral host epithelium defects were noticed in 2 eyes (1.7%) and fine microstriae in one eye (0.9%).

• None of the eyes developed interface inflammation or diffuse lamellar keratitis (DLK).

• None of the eyes developed remarkable transient light sensitivity syndrome (TLSS).

Late visual and refractive outcomes safetySafety index (postop to preop BCVA) at 1,3, and 6 months = 1.1.

Table 7: Changes (gain or loss) in Snellen’s lines of BCVA.

1 Month 3 Months 6 Months

2 lines gain 0% 1% 1%

1 line gain 36% 44% 52.1%

Unchanged 62% 53% 44.8%

1 line loss 2% 2% 2.1%

2 lines loss 0% 0% 0%

Changes in BCVA in terms of Snellen’s lines.

Late visual and refractive outcomes (Efficacy)Efficacy index (postop UCVA to preop BCVA) at 1,3, and 6 months = 1.0.

Time course of logMAR UCVA at 1,3, and 6 months.

Late visual and refractive outcomes Efficacy- Total rms

Table 10: Total rms at 1, 3, and 6 months.

Minimum Maximum Mean Std. Deviation

Preop. rms 0.14 0.81 0.3633 0.13198

1 Month rms 0.12 0.90 0.5432 0.20781

3 Months rms 0.15 0.94 0.5804 0.22879

6 Months rms 0.14 0.86 0.5400 0.20185

# Sig. increase at 1 m.# Non-sig. increase at 3 m.# Back to the 1 m level at 6 m.

Late visual and refractive outcomes Predictability- Attempted vs achieved correction at 6 m

Late visual and refractive outcomes Safety

• Visante OCT high resolution corneal scan obtained at 6 months postop.

Conclusions• In this study, IntraLase was proved to be a safe,

efficient, and a highly predictable means of LASIK flap creation.

• The IntraLase femtosecond laser has significantly reduced the incidence of LASIK flap complications. In addition to that reduction, IntraLase flap complications are much easier to manage than those of the mechanical microkeratome. Accordingly, IntraLase is becoming recognized as a safer method of flap creation.

• Its excellent efficacy and predictability with more predictable flap parameters make the IntraLase a very helpful tool in refractive surgery.

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