Central corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system

doi:10.1016/j.ophtha.2003.09.027

Ophthalmology

Volume 111, Issue 5, May 2004, Pages 875-879

https://doi.org/10.1016/j.ophtha.2003.09.027 Get rights and content

Abstract

Objective

To compare the reliability of central corneal thickness measurements (CCT) obtained with partial coherence interferometry (PCI), ultrasound pachymetry, and the Orbscan system.

Design

Cross-sectional study.

Participants

Twenty healthy subjects with CCT measurements in both eyes.

Methods

The CCT measurements were obtained with PCI, ultrasound pachymetry, and the Orbscan system. In each eye, 2 investigators performed 5 repeated measurements with each pachymetric device. Intraclass correlation coefficients (κ) were calculated and mean CCT measurements were compared.

Main outcome measures

The CCT measurements obtained with ultrasound pachymetry, the Orbscan system (Orbtek Inc., Salt Lake City, UT), and PCI.

Results

Mean CCT values measured with ultrasound pachymetry were significantly thicker than those measured with PCI (21.5 μm; P<0.001) or the Orbscan system (19.8 μm; P<0.001). The correlation coefficients for the intraobserver variability were 0.999 for PCI measurements, 0.983 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. The correlation coefficients for the interobserver variability were 0.998 for PCI measurements, 0.980 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. There was a slightly better consistency between ultrasound pachymetry and PCI (κ = 0.96) than between the Orbscan system and PCI (κ = 0.92) and between ultrasound pachymetry and the Orbscan system (κ = 0.89).

Conclusions

Partial coherence interferometry was the method with the least intraobserver or interobserver variability. Mean CCT as measured with ultrasound pachymetry was approximately 20 μm thicker than with the Orbscan system and PCI. However, corneal thickness measurements with ultrasound pachymetry and PCI were slightly more consistent than those of the Orbscan system and PCI. This slightly better consistency, however, may be important, especially in corneal refractive surgery.

Section snippets

Subjects and methods

After the study protocol was approved by the Ethics Committee of Vienna University School of Medicine, 20 healthy subjects were studied. The nature of the study was explained and all subjects gave written consent to participate. The mean age of the 18 women and 2 men was 28.1 years (range, 22–34 years). Exclusion criteria were any eye disease, contact lens use of less than 12 hours before measurements, a cylindrical error of more than 1.5 diopters (D), a spherical myopic error of more than 6 D,

Results

In each of the 40 eyes, 2 investigators performed 5 measurements with each pachymetric device. In sum, 1200 measurements were used for statistical analysis.

Discussion

The results of the present study show that PCI is the method with the least intraobserver and interobserver variability among the tested techniques. Reproducibility of the data obtained with the Orbscan system and ultrasound pachymetry was worse but still acceptable, as has been shown in previous studies.17, 18 We found that data obtained with ultrasound pachymetry showed a better correlation with PCI data than data measured with the Orbscan system. In corneal refractive surgery, however, both

References (21)

C.K Joo et al.
Corneal ectasia detected after laser in situ keratomileusis for correction less than −12 diopters of myopia
J Cataract Refract Surg
(2000)
C Argento et al.
Corneal ectasia after laser in situ keratomileusis
J Cataract Refract Surg
(2001)
V Yaylali et al.
Corneal thickness measurements with the Orbscan Topography System and ultrasound pachymetry
J Cataract Refract Surg
(1997)
W Drexler et al.
Investigation of dispersion effects in ocular media by multiple wavelength partial coherence interferometry
Exp Eye Res
(1998)
G Rainer et al.
Comparison of ultrasound pachymetry and partial coherence laser interferometry in the measurement of central corneal thickness
J Cataract Refract Surg
(2002)
M.J Doughty et al.
Human corneal thickness and its impact on intraocular pressure measuresa review and meta-analysis approach
Surv Ophthalmol
(2000)
M.A Fakhry et al.
Comparison of corneal pachymetry using ultrasound and Orbscan II
J Cataract Refract Surg
(2002)
N.C Wheeler et al.
Reliability coefficients of three corneal pachymeters
Am J Ophthalmol
(1992)
S.D McLeod et al.
Iatrogenic keratoconuscorneal ectasia following laser in situ keratomileusis for myopia
Arch Ophthalmol
(2000)
P Vinciguerra et al.
Prevention of corneal ectasia in laser in situ keratomileusis
J Refract Surg
(2001)

There are more references available in the full text version of this article.

Cited by (97)

Repeatability and Agreement of Orbscan II, Pentacam HR, and Galilei Tomography Systems in Corneas With Keratoconus
2017, American Journal of Ophthalmology
To assess the repeatability and agreement of keratometry and pachymetry measurements obtained using 3 tomographers in eyes with keratoconus.
Reliability analysis.
setting: Institutional. study population: Fifty eyes of 50 participants with keratoconus. observational procedure: Steep keratometry, flat keratometry, central corneal thickness (CCT), and thinnest corneal thickness (TCT) measurements using Galilei, Orbscan II, and Pentacam HR. main outcome measures: Repeatability was assessed using within-subject standard deviation (S_W), coefficient of variation (CV), and intraclass correlation coefficient (ICC). Bland-Altman plots and 95% limits of agreement (LoA) were used to evaluate agreement between device pairs.
For all studied parameters, ICC was >0.97 with the least repeatable measurements obtained using Orbscan II. Mean steep keratometry values were similar while mean flat keratometry values were significantly different between all devices. The Galilei and Pentacam HR had the lowest 95% LoA for both CCT and TCT. There were no significant differences in mean CCT between Galilei and Pentacam HR. Mean Orbscan II CCT measurements were not significantly different overall but had wide 95% LoA with Pentacam HR (−47.95 to 58.09 μm) and Galilei (−43.70 to 53.91 μm). Mean Orbscan II CCT measurements were significantly lower when an acoustic factor of 0.92 was applied (−33.6 μm vs Pentacam HR, P < .001; −33.6 μm vs Galilei; P < .001).
Keratometric and pachymetric measurements of keratoconic eyes obtained by Galilei, Orbscan II, and Pentacam were disparate. Measurements were less repeatable with Orbscan II compared with Pentacam HR and Galilei, although overall repeatability was high for all instruments.
Pentacam vs SP3000P specular microscopy in measuring corneal thickness
2015, Contact Lens and Anterior Eye
Citation Excerpt :
The patient sat in front of the device, placed the chin on a chin rest and was asked to keep both eyes open and to fixate on a blinking fixation target in the center of the camera. As soon as the image was perfectly aligned, the patient was asked not to move and the eyes open, and the scan was started [14,15]. The center of the cornea is measured in each of the single images of a scan.
To compare corneal thickness (CT) measurements obtained with SP3000P specular microscope and Pentacam in eyes screened to undergo refractive surgery (RS).
In this prospective study, a non-randomized consecutive series of 73 healthy eyes (age range: 14–78 years; mean = 38.4 ± 14.9) underwent CT measurement with both Oculus Pentacam and Topcon SP3000P specular microscope to assess their suitability to undergo corneal RS.
CT measurements with SP3000P ranged from 451 to 609 μs (mean 523.1 ± 34.4 μs). The measurements obtained with Pentacam ranged at the corneal apex from 477 to 672 μs (mean 558.9 ± 38.9 μs), at the pupil center from 477 to 672 μs (mean 557.9 ± 38.9 μs) and at the thinnest point from 474 to 669 μs (mean 551.1 ± 39.4 μs). CT measurements showed a good correlation but a statistically significant difference at the pupil center (mean −34.9 ± 14.6 μs, R² = 0.860, p < 0.001), at the apex (mean −35.9 ± 14.9 μs, R² = 0.856, p < 0.001) and at the thinnest point (mean −32 ± 14.8 μs, R² = 0.862, p < 0.001). The calculated regression formulas were: y = 0.816x + 66.94 for the apex, y = 0.819x + 66.07 for the pupil center and y = 0.810x + 73.13 for the thinnest point; where y is the CT measured with the SP3000P and x is the measurement obtained with the Oculus Pentacam.
Our results suggest that SP3000P measures thinner corneas compared to the Pentacam and that the correcting factor we identified should be applied to make comparisons between these two devices.
Anterior chamber depth measurement in teenagers. Comparison of two techniques
2013, Journal of Optometry
The aim of this study is to determine the anterior chamber depth (ACD) in teenagers using two different devices: partial coherence interferometry IOLMaster (Carl Zeiss Meditec) and anterior segment optical coherence tomography (Visante™ OCT, Carl Zeiss Meditec) and to evaluate the degree of agreement between ACD measurements carried out by both instruments.
In this prospective study 68 eyes of 34 emmetropic Caucasic patients (18 girls and 16 boys) were analysed. ACD was measured from the anterior corneal surface to anterior surface of the crystalline lens. For each age the ACD size was calculated and the difference between IOLMaster and Visante-OCT measurements was analysed using Bland–Altman plot and paired t-test.
For all data the mean (SD) anterior chamber depth was 3.56 (0.19) mm with the IOLMaster and 3.65 (0.21) mm with the Visante-OCT. IOLMaster measurements were an average of 0.10 (0.12) mm less than Visante-OCT (paired t-test, p < 0.0001).
In our study ACD mean differences (SD) by age obtained had been −0.139 (0.163), −0.044 (0.112), −0.082 (0.054) and −0.105 (0.101) for 13, 14, 15 and 17 respectively. The 13-age group showed the larger standard deviation compared to the other groups.
IOLMaster and Visante-OCT are good and useful non-contact methods for measuring ACD in the healthy eyes of teenagers. The measurement differences between two devices were quite small, however, they should take into account in order to calculate the power on intraocular lens. The findings provide more normative date for this age group.
El objetivo de este estudio es determinar la profundidad de la cámara anterior en adolescentes, utilizando dos dispositivos diferentes: la interferometría de coherencia parcial IOLMaster (Carl Zeiss Meditec) y la tomografía de coherencia óptica del segmento anterior (Visante™ OCT, Carl Zeiss Meditec), así como evaluar el grado de concordancia entre las mediciones de la profundidad de la cámara anterior realizadas, utilizando ambos instrumentos.
En este estudio prospectivo se analizaron 68 ojos de 34 pacientes caucásicos emetrópicos (18 chicas y 16 chicos). Se midió la profundidad de la cámara anterior desde la superficie anterior de la córnea a la superficie anterior del cristalino. Se calculó el tamaño de la profundidad de la cámara anterior para cada grupo de edad, y se analizó la diferencia entre las mediciones con IOLMaster y Visante-OCT, utilizando el gráfico Bland-Altman y la prueba de t pareada.
Para todos los datos, la profundidad de la cámara anterior media (DE) fue de 3,56 (0,19) mm con IOLMaster y de 3,65 (0,21) con Visante-OCT. Las mediciones con IOLMaster fueron de media 0,10 (0,12) mm menores que las realizadas con Visante-OCT (Prueba de t pareada, p < 0,0001).
En nuestro estudio, las diferencias medias (DE) de la profundidad de la cámara anterior por edad fueron de -0,139 (0,163), -0,044 (0,112), -0,082 (0,054) y -0,105 (0,101) para los grupos de 13, 14, 15 y 17 años, respectivamente. El grupo de 13 años aporta una desviación estándar superior a la del resto de grupos estudiados.
IOLMaster y Visante-OCT constituyen métodos de no contacto buenos y útiles para la medición de la profundidad de la cámara anterior en los ojos sanos de adolescentes. Las diferencias de medición entre ambos dispositivos fueron bastante pequẽnas, sin embargo, estas diferencias deberían tenerse en cuenta para el cálculo de la lente intraocular. Los hallazgos son interesantes ya que aportan más datos normativos para este grupo de edad.
Keratoconus: exploring fundamentals and future perspectives – a comprehensive systematic review
2024, Therapeutic Advances in Ophthalmology
Keratoconus Diagnosis: From Fundamentals to Artificial Intelligence: A Systematic Narrative Review
2023, Diagnostics
Clinical Examination and Diagnostic Testing
2022, Albert and Jakobiec's Principles and Practice of Ophthalmology: Fourth Edition

View all citing articles on Scopus

^☆

Manuscript no. 230021.

None of the authors has a proprietary interest in any product mentioned.

View full text

Original articleCentral corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system☆

Abstract

Objective

Design

Participants

Methods

Main outcome measures

Results

Conclusions

Section snippets

Subjects and methods

Results

Discussion

J Cataract Refract Surg

J Cataract Refract Surg

J Cataract Refract Surg

Exp Eye Res

J Cataract Refract Surg

Surv Ophthalmol

J Cataract Refract Surg

Am J Ophthalmol

Iatrogenic keratoconuscorneal ectasia following laser in situ keratomileusis for myopia

Arch Ophthalmol

Prevention of corneal ectasia in laser in situ keratomileusis

J Refract Surg

Original article
Central corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system☆