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Published byAndra Parsons Modified over 9 years ago
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Mohamed A Guenena, MD Helga P Sandoval, MD, MSCR, Kerry D Solomon, MD Magill research center for vision correction Storm Eye Institute Medical University of South Carolina
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To assess the accuracy and reproducibility of flap thickness created by the fifth generation femtosecond laser using: Intraoperative pachymetry Postoperative anterior segment OCT ASCRS 2009
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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 ASCRS 2009
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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 ASCRS 2009 ABCD Line 1 Line 2 Line 3 Line 4
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Pre and Postoperative Data Intraoperative Pachymetry was done by subtraction method ASCRS 2009 Pre-operativePost-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 flaps110 µm flaps Number of eyes418 Flap thickness by US pachymetry 109 µm (±9.6)119 µm (±11.5)
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ASCRS 2009 OCT picture showing the four points measurements for a single line scan in a patient who had a 110 µm flap
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Attempted Flap thickness Number of eyes OCT measurements Mean Std Dev 100 µm2117 µm11.2 110 µm4123 µm6.5 ASCRS 2009 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 APoint BPoint CPoint D Average thickness 119 µm (±10.9) 124 µm (±4.4) 124 µm (±7.5) 124 µm (±6.4)
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Comparing the flap thickness by lines for the 110µm group ASCRS 2009 Line 1Line 2Line 3Line 4 Average thickness 121 µm (±7.1) 124 µm (±5.5) 124 µm (±7.4) 124 µm (±6)
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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 ASCRS 2009
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