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
Central Corneal Thickness
Central Corneal Thickness
Anterior Chamber Depth
Anterior Chamber Depth
Biometric TechnologyBiometric Technology
Indicator for corneal metabolism and hydration status
Important parameter in characterization of corneal disease
Basic parameter in the planning of laser refractive surgery
Partial Coherent Interferometry
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
Determine the actual position of the lens.
Assessment of accommodation-induced configuration changes of the phakic eye
Useful parameter in the planning of lens refractive surgery
Accurate and reliable determination of anterior segment biometry is important in laser and lens refractive surgery
Ultrasound pachymetry has been the traditional “gold standard” for biometry measurement. However, the are newer non-contact optical technologies available.
Scheimpflug ImagingSlit scanning Anterior Segment OCT
The study is to compare two different
non-contact
Purpose
Methods
Cross sectional
Prospective
108 healthy eyes
54 subjects aged 20-25 years old
IIUM Eye Specialist Clinic Kuantan Pahang.
Central Corneal Thickness
Anterior Chamber Depth
Strategy Strategy SubjectsSubjects MeasurementsMeasurements
Anterior Segment Optical Coherent Tomography
Scheimpflug Imaging
ToolsTools
In measuring
Anterior Chamber
Depth
Central Corneal
Thickness
Anterior Segment Optical Coherent Tomography (ASOCT)
The image-acquisition system provides a video image of the examined zone and stores the last 7 images at a rate of 8 frames per second
The software interprets the selected image.
The image is reconstructed to provide biometry information
Anterior Segment Optical Coherent Tomography (ASOCT)
The image-acquisition system provides a video image of the examined zone and stores the last 7 images at a rate of 8 frames per second
The software interprets the selected image.
The image is reconstructed to provide biometry information
Scheimpflug Imaging (SI)
Sectional image were measured and recorded
CCD camera rotates and provides section planes from three spatial
planes
The measured data obtained are used to calculate a 3D model from which the
thickness and the anterior chamber depth can be computed
Scheimpflug Imaging (SI)
Sectional image were measured and recorded
CCD camera rotates and provides section planes from three spatial
planes
The measured data obtained are used to calculate a 3D model from which the
thickness and the anterior chamber depth can be computed
Result
Variables Mean (SD) µm
Mean difference (95% CI) µm
p-value
CCT (ASOCT) 526.61 (28.06) -13.42 (-14.54 to -11.95) p<0.05
CCT (Scheimpflug) 539.85 (27.01)
Variables Mean (SD) µm
Mean difference (95% CI) µm
p-value
ACD (ASOCT) 3.17 (0.23) 0.06 (0.05 to 0.07) p<0.05ACD (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
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
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.
460 480 500 520 540 560 580 600 620
5
0
-5
-10
-15
-20
-25
-30
-35
AVERAGE of CCTVisante and CCTPentacam
CC
TV
isan
te -
CC
TP
enta
cam
Mean
-13.2
-1.96 SD
-26.5
+1.96 SD0.1
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
AVERAGE of ACDVisante and ACDPentacamA
CD
Vis
ante
- A
CD
Pen
taca
m
Mean
0.06
-1.96 SD
-0.08
+1.96 SD
0.20
Result
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.
References1. Al-Mezaine H. S., Al-Amro S. A., Kangave D., Sadaawy A., Wehaib T. A., Al-
Obeidan S. Comparison Between Central Corneal Thickness Measurements by Oculus Pentacam and Ultrasonic Pachymetry. Int Ophthalmol 2007.
2. Barkana Y. Gerber Y. Elbaz U., Schwartz S., Ken-Dror G., Avni I., Zadok D. Central Corneal Thickness Measurement with the Pentacam Scheimpflug System, Optical Low Coherence Reflectometry Pachymetry and Ultrasound pahcymetry. J Cataract Refract Surg 2005; 31: 1729-1735.
3. Buehl, W., Stojanac, D., Sacu, S., Drexler, W., & Findl, O. (2006).Comparison of three methods of measuring corneal thickness and anterior chamber depth. American Journal of Ophthalmology, 141, 1.
4. Meinhardt, B., Stachs, O., Stave, J., Beck, R., & Guthoff, R. (2006). Evaluation of biometric methods for measuring the anterior chamber depth in the non-contact mode. Graefe’s Arch Clinical Experimental Ophthalmology, 244, 559-564.
5. Wolffsohn, J. S., & Peterson, R. C. (2006). Anterior ophthalmic imaging. Clinical and Experimental Optometry, 89, 4, 205-214.
6. Wolffsohn, J. S., & Davies, L. N. (2007). Advances in anterior segment imaging. Current Opinion in ophthalmology, 18, 32-38.
