Transcript Correction of Myopia and Myopic Astigmatism with the

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
Financial Interest Disclosure
• Dr. Manche is a consultant for
PriaVision, Inc.
• Dr. Manche is an investor in Calhoun
Vision, Inc. and Ophthonix, Inc.
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
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
Design: Technique
•
•
•
•
60 kHz IntraLase femtosecond laser
Programmed flap thickness: 100 um
Sonogage ultrasonic pachymetery
Visante OCT imaging device
Results
Intra-operative
Post-operative
Subtraction Pachymetry Anterior Segment OCT
93.0 ± 14.3 um
104.2 ± 5.5 um
100 micron programmed depth
Range: 64-125
100 micron programmed depth
Range: 90-115
OCT Image of Lasik Flap
Flap thickness (um)
Mean Pachymetry Measurements
Patients
Flap thickness (um)
Mean Anterior OCT
Measurements (+ Ranges)
Patients
Flap thickness (um)
Mean Anterior OCT vs.
Pachymetry Measurements
Patients
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
References
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flap with anterior segment OCT imaging prior to planned LASIK retreatment surgery. J
Refract Surg. 2008 Feb;24(2):197-9.
3. Stahl JE, Durrie DS, Schwendeman FJ, Boghossian AJ. Anterior segment OCT
analysis of thin IntraLase femtosecond flaps. J Refract Surg. 2007 Jun;23(6):555-8.
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segment imaging: a new era for ophthalmic diagnosis? Br J Ophthalmol. 2007
Apr;91(4):551-7. Review.
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