Transcript Evaluation of Regional Pachymetry Index and Posterior

Comparison of Central Corneal Thickness and Anterior Chamber
Depth Measurements between Anterior Segment Optical Coherence
Tomography and Scheimpflug Imaging
Khairidzan Mohd Kamal MD
Department of Ophthalmology, Faculty of Medicine, International Islamic University Malaysia
The author have no financial interest in the
subject matter of this poster
Introduction
Accurate and reliable determination of anterior segment biometry is important
in laser and lens refractive surgery
Central Corneal
Thickness
Anterior Chamber
Depth
Indicator for corneal metabolism and hydration status
Determine the actual position of the lens.
Important parameter in characterization of corneal disease
Assessment of accommodation-induced configuration changes of
the phakic eye
Basic parameter in the planning of laser refractive surgery
Useful parameter in the planning of lens refractive surgery
Ultrasound pachymetry has been the traditional “gold standard” for biometry
measurement. However, the are newer non-contact optical technologies available.
Biometric Technology
Slit scanning
Anterior Segment OCT
Partial Coherent Interferometry
Scheimpflug Imaging
We sought to evaluate the comparability of different non-contact methods for the analysis
of the central corneal thickness and anterior chamber depth in the phakic eye
Purpose
The study is to
compare two different
non-contact
Central
Corneal
Thickness
In measuring
Anterior
Scheimpflug
Segment Optical
Imaging
Coherent
(SI)
Tomography (ASOCT)
Sectional image were measured and
Methods
The image-acquisition
recorded
system provides a
video image of the examined zone
CCD camera rotates and provides
Strategy
Subjects
Tools
and stores the last 7 images
at a rate
section planes from three spatial
of 8 frames per second
planes
 108 healthy eyes
Anterior
The software interprets the selected
Segment Optical
The measured
dataobtained
are used
Cross
54 subjects
aged
image.sectional
Coherent
to calculate a 3D model
from which
20-25
years
old
Prospective
Tomography
The
image
the thickness
is reconstructed
and thetoanterior
provide
 IIUM
Eye
biometry
chamber
information
depth can
be computed
Scheimpflug
Specialist Clinic
Imaging
Kuantan Pahang.
Anterior
Chamber
Depth
Measurements
Central
Corneal
Thickness
Anterior
Chamber Depth
Result
Variables
CCT (ASOCT)
Mean
(SD) µm
526.61 (28.06)
Mean difference
p-value
(95% CI) µm
-13.42 (-14.54 to -11.95) p<0.05
CCT (Scheimpflug) 539.85 (27.01)
Variables
ACD (ASOCT)
Mean
(SD) µm
3.17 (0.23)
Mean difference
(95% CI) µm
0.06 (0.05 to 0.07)
p-value
p<0.05
ACD (Scheimpflug) 3.11 (0.24)
The mean difference (95% CI) of CCT between the methods was 13.42 (± 6.79) µm with p
value <0.05. The mean difference in ACD between the methods was 0.06 (±0.072) mm
with p value <0.05
Result
In Pearson’s correlation, the observed linear correlation between
ASOCT and Scheimpflug score was r = 0.972 for CCT. The
observed linear correlation between ASOCT and Scheimpflug
score was r = 0.956 for ACD.
Result
5
0.3
+1.96 SD
0.1
0
ACDVisante - ACDPentacam
-5
-10
-15
-20
-25
+1.96 SD
0.20
0.2
0.1
Mean
Mean
-13.2
0.06
0.0
-1.96 SD
-0.08
-0.1
-1.96 SD
-26.5
-0.2
-30
-35
-0.3
460
480
500
520
540
560
580
AVERAGE of CCTVisante and CCTPentacam
600
620
2.4
2.6
2.8
3.0
3.2
3.4
AVERAGE of ACDVisante and ACDPentacam
3.6
In Bland –Altman analysis, Approximately 105/108 (95%)
ASOCT-Scheimpflug differences were within the 95% CI interval
for the mean difference of CCT. Approximately 106/108 (94%)
ASOCT-Scheimpflug differences were within the 95% CI interval
for the mean difference of the mean difference of ACD.
3.8
Discussion
1. This study can serve as the basis of the clinical decision making in
the comparison between ASOCT and Scheimpflug imaging.
2. The Central Cornea Thickness (CCT) measurement using
Scheimpflug Imaging was higher by 13. 42±6.79 µm than ASOCT
3. For Anterior Chamber Depth (ACD), ASOCT provided higher
measurement compared to Scheimpflug imaging by 0.06±0.072
mm. These result a statistical significant difference.
4. Both instruments had a good correlation and agreement in
measuring CCT and ACD.
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