Study of Flap Thickness Precision with a Femtosecond Laser - PowerPoint PPT Presentation

1 / 12
About This Presentation
Title:

Study of Flap Thickness Precision with a Femtosecond Laser

Description:

The thickness of the flaps was calculated by the following equation: ... Creating more reliable and better flaps are possible by implementing this method, ... – PowerPoint PPT presentation

Number of Views:84
Avg rating:3.0/5.0
Slides: 13
Provided by: Yone1
Category:

less

Transcript and Presenter's Notes

Title: Study of Flap Thickness Precision with a Femtosecond Laser


1
Study of Flap Thickness Precision with a
Femtosecond Laser
  • Shinagawa LASIK Center
  • Tatsuya Yonekawa,MSc Minoru Tomita,MD.PhD
  • Youhei Iida,CE Yuko Inada,CE Sachiko
    Imada,BSc Mika Morizumi,BSc
  • Masashi Shimizu,BSc Hiroyuki Nomura,CE
    Naoyuki Kurokawa, MD
  • Yutaka Makisima, MD Nobuo Nakamura, MD. PhD
    Tadayuki Nakamura, MD
  • Masaru Aoyama, MD Tadahiko Tsuru, MD.PhD

2
Introduction
  • Recently, many authors have reported advantages
    of corneal flap preparation using Femtosecond
    laser(FS 60AMO).
  • FS 60 requires Patient Interface (PI) for
    connection with the patient.
  • FS 60 can make corneal flaps with precise
    thickness (Planar-Flap) by the applanation of the
    cornea with PI.

applanation
Planar-Flap
3
Purpose
  • During operation , we often encounter
    occasions that flap thickness differs from the
    input value.
  • May it have an individual error in PI?
    Isn't it a possibility of the effect of PI that
    the flap thickness is different from the input
    value?
  • Therefore, we measured PI by the measuring
    device.
  • Error value corrected in correlation to PI
    regulation.
  • Corrected value is inputted (manually correction)
    into FS60 .
  • (Shinagawa method)
  • We studied whether we could make a flap without
    errors.

4
Subjects and methods
  • The subjects were 240 eyes of 120 patients (mean
    age 34.65 years old, mean cornea thickness
    538.4923.91um) who underwent LASIK using
    measured PI with FS 60 at our clinic from July
    2007 to September 2007.
  • The thickness of the flaps was calculated by the
    following equation
  • Subtraction pachymetry method
  • (pre-operative cornea thickness - post
    lifting bed thickness).
  • The corneal thickness was determined by a
    contact ultrasonic pachymater (SP3000Tomey).
  • The subjects were divided into two groups by
    flap thickness 90 um group (98 eyes) and 100
    um group (152 eyes).
  • IntraLase FS60
  • Raster flap mode (Power 0.80uJ)
  • 9.0 mm 8.8 mm diamater
  • Hinge angle was 60 degree (superior
    type)
  • Side-cut angle was 70 degree (Power
    0.80uJ)

5
Method of PI measurement
  • Sterilized clinical engineer picked PI (n531)
    randomly under the clean room and examined for
    measurement right before the operation.
  • Using an precise measuring device (IDH0530
    Mitutoyo), we measured five spots without
    damaging the PI lens surface.
  • We limited the measurement range to be 10µm,
    within the range of official PI error by the
    manufacturer.
  • Utilized the PI with lens tilt of 5um or less.
  • PI error was determined by the difference between
    the value from the lens center and the PI
    regulation by the manufacturer.

6
Result of PI measurement
  • n153

7
Input for Correction
  • PI does have few errors. PI thickness can differ
    a little and it effects the flap thickness.
  • We want to make a flap according to the corrected
    value, thus less errors.
  • Therefore, we measured PI thickness before
    surgery to make corneal flaps with more correct
    thickness.
  • Our method utilizes a measured PI
  • Input for correction (Shinagawa method) is
    necessary!
  • A flap thickness of 100um is made at the time of
    100um input in PI of 0um
  • As for PI of a error,
  • a flap is made thinner
  • As for PI of a - error,
  • a flap is made thicker
  • We defined PI correction value to be the
    difference between the PI standard value of 0um
    and the value from the lens center, which was
    reflected onto the system of FS60 laser.

PI regulations ?
Thin !!
Thick !!
8
Flap Results?
9
Flap Results?
  • measured PI 90µm
  • Measured PI 100µm

p Value
p Value
10
Summary
  • The mean flap thickness was 92.184.11um
    (Range82-99um) in 90 um group, and 102.344.93um
    (Range91-112um) in 100 um group.
  • In the flap, a right and left correlation was not
    seen.

11
Conclusions
  • We could reduce the errors for flap thickness by
    measuring PI value and making correction
    manually.
  • Creating more reliable and better flaps are
    possible by implementing this method, measured PI
    value, for all operations.
  • When making thin flap is needed, by controlling
    input values for less errors, foreseeable
    accidents and troubles can be avoided.
  • The flap with good accuracy was able to be
    achieved in reproducibility good by applying
    this measured PI to all the operations.
  • The present study shows that the use of measured
    PI enables to make flaps with more precise
    thickness than the method using unmeasured PI as
    reported by Binder et al J Cataract Refract Surg
    2004 301-9.
  • We will classify the combination with anterior
    segment OCT into a field in the future.

12
References
  • Flap dimensions created with the Intralase
    pulsion laser . Binder et al
    J Cataract Refract Surg 2004 301-9.
  • Anterior Segment OCT Analysis of Thin IntraLase
    Femtosecond Flaps . Jason E.Stahl et al Journal
    of Refract Surgery 2007 Vol23555-558
  • Flap thickness reproducibility in laser situ
    keratomileusis with a femtosecond laser Optical
    coherence tomography measurement.
  • Jin-Hyoung Kim et al J Cataract Refract
    Surg 2008 34132-136.
Write a Comment
User Comments (0)
About PowerShow.com