FIFTH GENERATION FEMTOSECOND LASER FLAP THICKNESS

Mohamed A Guenena, MDHelga P Sandoval, MD, MSCR, Kerry D Solomon, MD

Magill research center for vision correctionStorm Eye Institute

Medical University of South CarolinaFINANCIAL DISCLOSURE: None of the authors has any financial interest in any product mentioned hereinMohamed A. Guenena: NoneHelga P. Sandoval: Alcon Laboratories, Inc. - D; Allergan, Inc. - D; Abbott Medical Optics - DKerry D. Solomon: Alcon Laboratories, Inc. - A,C,D; Allergan, Inc. - A,C,D; Abbott Medical Optics - A,C,D; Advanced Vision Research -  A,C,D; Bausch & Lomb, Inc. -  A,C,D; Eyemaginations -  A,C,D; QLT, Inc. -  A,C,D

PURPOSE

To assess the accuracy and reproducibility of flap thickness created by the fifth generation femtosecond laser using:Intraoperative pachymetry Postoperative anterior segment OCT

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METHODS

Prospective, unmasked study 24 eyes of 12 patients Had primary LASIK surgery Flaps created with the new 5th generation femtosecond Laser (iFS

Advanced Femtosecond Laser, Abbot Medical Optics ) Attempted Flap depth

100 microns in 4 eyes 110 microns in 20 eyes

Assessment: Intraoperative pachymetry Postoperative anterior segment Fourier-domain optic coherence tomography

(OCT) on a subgroup of patients at an average of 3 month The SAS system software was used to analyze the results

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OCT SETTINGS:

2 cross scans were used to measure each flap (Figure 1) The cross scan setting entails 2x1024 A scans (8 scans in each directions are then averaged)

The LASIK flap was identified by increased reflectivity at the flap-stromal interface. then the cursor was moved manually to the interface and measurements were

recorded. On each line of the cross scan, the thickness was calculated at four points ( Figure 2)

A 2.5 mm left to the midline B 1 mm left to midline C 1 mm right to midline D 2.5 mm right to midline

Fig. 1 Fig. 2

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A B C D

Line 1

Line 2 Line 3Line 4

Pre and Postoperative Data

Intraoperative Pachymetry was done by subtraction method

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Pre-operative Post-operative day

30

Spherical error -2.5 (-6.2—2.2) 0.1 (-0.2―1.2)

Cylinder -0.7 ( -3.5―0.5) -0.2(-0.5―0)

Spherical equivalent

-2.73 (-7.75― 2.25) 0 (-0.37―0.25)

Pachymetry 565 ( 535―596) NA

100 µm flaps 110 µm flaps

Number of eyes 4 18

Flap thickness by US pachymetry

109 µm (±9.6) 119 µm (±11.5)

RESULTS

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OCT picture showing the four points measurements for a single line scan in a patient who had a 110 µm flap

OCT RESULTS

Attempted Flap thickness

Number of eyes

OCT measurementsMean

Std Dev

100 µm 2 117 µm 11.2

110 µm 4 123 µm 6.5

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Overall flap thickness per group

Comparing the consistency of the flap thickness at different points in the 110 µm group in all line scans

Point A Point B Point C Point D

Average thickness

119 µm (±10.9)

124 µm (±4.4)

124 µm (±7.5)

124 µm (±6.4)

OCT RESULTS

Comparing the flap thickness by lines for the 110µm group

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Line 1 Line 2 Line 3 Line 4

Average thickness

121 µm (±7.1)

124 µm(±5.5)

124 µm(±7.4)

124 µm(±6)

CONCLUSION

The new fifth generation femtosecond laser

shows

High consistency of flap thickness

High reproducibility of flap thickness

Accurate flap thickness predictability

The flaps are uniform at different points

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ASCRS 2009

ASCRS 2009

Thank you