1. Measurement of 60 kHz Femtosecond LASIK Flaps with Anterior Segment Ocular Coherence Tomography & Ultrasonic Subtraction Pachymetry
Edward E. Manche, MD Yohko Murakami, BA, MA
Stanford University School of Medicine

2. Financial Interest Disclosure
Dr. Manche is a consultant for PriaVision, Inc.
Dr. Manche is an investor in Calhoun Vision, Inc. and Ophthonix, Inc.

3. Purpose
Prospectively measure intra-operative ultrasonic subtraction pachymetry flap thickness and compare to post-operative anterior segment optical coherence tomography (OCT) flap thickness in eyes undergoing LASIK with a 60 kHz femtosecond laser

4. Design 32 eyes of 32 subjects Prospective study
Eyes treated with IntraLase 60 kHz femtosecond laser
Ultrasonic subtraction pachymetry performed intra-operatively
Anterior segment ocular coherence tomography (Visante™ OCT) imaging of flap thickness performed at 3-month visit
5 measurements made of each flap
OCT measurements performed by single masked observer

5. Design: Technique 60 kHz IntraLase femtosecond laser
Programmed flap thickness: 100 um
Sonogage ultrasonic pachymetery
Visante OCT imaging device

6. Results Intra-operative Subtraction Pachymetry
Post-operative Anterior Segment OCT
93.0 ± 14.3 um 100 micron programmed depth
Range:
104.2 ± 5.5 um 100 micron programmed depth
Range:
Updated 10/10/05cg

7. OCT Image of Lasik Flap

8. Mean Pachymetry Measurements
Flap thickness (um)
Patients

9. Mean Anterior OCT Measurements (+ Ranges)
Flap thickness (um)
Patients

10. Mean Anterior OCT vs. Pachymetry Measurements
Flap thickness (um)
Patients
Patients

11. Conclusions
60 kHz femtosecond laser produces reliably uniform thin planar flaps
Poor correlation between intra-operative subtraction pachymetry and post-operative anterior segment OCT
Subtraction pachymetry consistently underestimated flap thickness compared to anterior segment OCT
Study suggests that intraoperative subtraction pachymetry may be less accurate and more prone to measurement error than post-operative anterior segment OCT measurements

12. References
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