Measurement of laser in situ keratomileusis

1
Measurement of laser in situ keratomileusis
flap thickness by anterior segment OCT(Visante)
Kwan Soo Kim1, Chul Young Choi1, Myoung Joon
Kim2, Hungwon Tchah2 1. Department of
Ophthalmology, Sungkyunkwan University School of
Medicine, Kangbuk Samsung Hospital, Seoul,
Korea. 2. Department of Ophthalmology,
University of Ulsan College of Medicine,
Asan Medical Center, Seoul, Korea.
2
Purpose

• To investigate the relationship between 1310-nm
  OCT, an ultrasonic pachymetry, and Orbscan ? in
  corneal thickness measurements of normal subjects
• To measure LASIK corneal flap thickness and
  residual stromal bed thickness using 1310-nm OCT

3
Methods

• Group 1 (corneal thickness measurment)
• Inclusion criteria
• - No ocular abnormality, contact lens wear
• - No ocular surgery
• - Refractive errors lt -6.0D
• Instruments (1 2 3)
• 1. Orbscan ? (Bausch Lomb, Rochester, NY)
  the thinnest point
• 2. 1310-nm OCT system(Visante OCT, Carl
  Zeiss, Meditec)
• the thinnest point
• 3. Ultrasonic pachymetry (DGH Technology Inc,
  Exton)
• the center of the pupil
• Corneal thickness values for the central were
  collected
• by the instruments.

4
Methods

• Group 2 (corneal flap thickness measurement)
• - 2006.5.11 2006.7.26
• - ASAN Medical Center
• - No ocular surgery
• Intraoperative
• 1. Intraoperative pachymetry
• 2. Residual bed pachymetry
• Estimated flap thickness 1 - 2
• Postoperative
• The central corneal thickness of flap were
  measured with
• 1310-nm OCT 1day, 1week, and 1month after surgery.

5
Results

• Patients characteristics

6
Results

• Central corneal thickness in group 1

ANOVA P0.012
7
Results

• Correlation between Ultrasonic pachymetry and
  OCT in group 1

Pearsons correlation coefficient r0.740
Plt.001)

• Correlation between Orbscan ? and OCT in group 1

Pearsons correlation coefficient r0.865,
Plt.001)
8
Results

• LASIK flap / Residual stromal bed thickness in
  group 2

9
Results
Decreased corneal reflectivity at the interface
Difficult to interpret !!
10
Conclusions

• Ultrasonic pachymetry produced the highest
  corneal thickness readings in the center,
  compared to Orbscan ? and OCT.
• OCT scan technique is the first non-contact
  device to image, measure and document both
  corneal flap thickness and residual stromal
  thickness immediately following LASIK surgery.
• The 1310-nm OCT is a valuable tool for corneal
  research and is able to provide information.