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Titre

Femtolasik flap thickness accuracy of the Zeiss 500 kHz Visumax femtosecond laser

But	To evaluate FEMTOLASIK flap thickness accuracy using Scheimpflug and ultrasound pachymetry.
Méthodes	A prospective study of 121 consecutive eyes who had flaps created with the 500 kHz VisuMax femtosecond laser (Carl Zeiss Meditec) were included for flap thickness evaluation. Preoperative pachymetry was performed with the Oculus Pentacam HR Scheimpflug imaging system, residual stromal thickness was measured with ultrasound pachymetry. Real flap thickness was calculated and compared to the intended theoretical flap thickness.
Résultats	All eyes underwent eventless femtosecond laser flap creation. No complications occurred. Side cut angle was 90 °, hinge position 0°, hinge angle 50° in all eyes. Scan direction was ‘spiral in’, energy offset was 29 mJ, track distance and spot distance was 3 µm at the flap and 1.5 µm at the flap side. The intended flap thickness was 110 µm in all eyes. The mean real achieved flap thickness was 109.06 ± 17.14 μm.
Conclusion	The flap creation with the VisuMax 500 kHz femtosecond laser was found to be highly predictable and accurate. Inaccuracy in measuring residual stromal thickness using ultrasound pachymetry, compared to the accurate preoperative pachymetry measured with the Oculus Pentacam HR Scheimpflug imaging system, may account for the relatively high standard deviation.

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