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Comparison of central corneal thickness: ultrasound pachymetry versus slit-lamp optical coherence tomography, specular microscopy, and Orbscan.

Khaja WA, Grover S, Kelmenson AT, Ferguson LR, Sambhav K, Chalam KV - Clin Ophthalmol (2015)

Bottom Line: Correlations (r (2)) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r (2)=0.98, P<0.0001), specular microscopy (r (2)=0.98, P<0.0001), and Orbscan (r (2)=0.96, P<0.0001).All modalities had a linear correlation with US pachymetry measurements.The four modalities showed significant linear correlations with one another.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, University of Florida, College of Medicine, Jacksonville, FL, USA.

ABSTRACT

Background: Central corneal thickness (CCT) can be measured by using contact and non-contact methods. Ultrasound pachymetry (US pachymetry) is a contact method for measuring CCT and is perhaps the most commonly used method. However, non-contact methods like scanning slit topography (Orbscan II), slit-lamp optical coherence tomography (SL-OCT), and specular microscopy are also used. Not many studies have correlated the measurement of CCT with all four modalities. The purpose of this study was to compare and correlate the CCT measurements obtained by US pachymetry with SL-OCT, specular microscopy, and Orbscan.

Method: This is a prospective, comparative study done in an institutional setting. Thirty-two eyes of 32 subjects with no known ocular disease and best-corrected visual acuity of 20/20 were enrolled. CCT measurements were obtained using SL-OCT, specular microscopy, scanning slit topography (Orbscan), and US pachymetry. Three measurements were made with each instrument by the same operator. Mean, standard deviation, and coefficient of variation were calculated for CCT measurements acquired by the four measurement devices. Bland-Altman plot was constructed to determine the agreements between the CCT measurements obtained by different equipment.

Results: The mean CCT was 548.16±48.68 μm by US pachymetry. In comparison, CCT averaged 546.36±44.17 μm by SL-OCT, 557.61±49.92 μm by specular microscopy, and 551.03±48.96 μm by Orbscan for all subjects. Measurements by the various modalities were strongly correlated. Correlations (r (2)) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r (2)=0.98, P<0.0001), specular microscopy (r (2)=0.98, P<0.0001), and Orbscan (r (2)=0.96, P<0.0001). All modalities had a linear correlation with US pachymetry measurements.

Conclusion: In subjects with healthy corneas, SL-OCT, specular microscopy, and Orbscan (with correction factor) can be used interchangeably with US pachymetry in certain clinical settings. The four modalities showed significant linear correlations with one another.

No MeSH data available.


Related in: MedlinePlus

Scatter plot display of ultrasound pachymetry with specular microscopy measurement of CCT (r2=0.98).Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness.
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f5-opth-9-1065: Scatter plot display of ultrasound pachymetry with specular microscopy measurement of CCT (r2=0.98).Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness.

Mentions: The Bland–Altman plot showed that the measurements acquired via US pachymetry were greater than those obtained by SL-OCT for mean CCT values from 475–550 μm (Figure 1). For CCT values beyond 550 μm SL-OCT measurements were higher than US pachymetry. The mean (± SD) CCT measurement difference between the two methods was 1.24 (±4.51) μm, and the 95% limits of agreement (LOA) were between −21.76 and 18.18 μm. US pachymetry measurements when compared to specular microscopy, showed an overall decrease in measurement values for CCT when values ranged from 500 to 650 μm (Figure 2). In this case mean (±SD) difference was 8.69 (±1.24) μm while the 95% LOA range was −8.82 to 27.4 μm (Figure 2). Bland–Altman plot comparison of CCT measurements obtained by US pachymetry vs Orbscan II (Figure 3) demonstrated that US pachymetry showed little relative difference in CCT measurements within the range of 500–650 μm as compared to Orbscan. Table 2 shows that the mean (±SD) difference between US pachymetry and Orbscan II was 2.8 (±0.28) μm with a 95% LOA range between −30.15 and 24.40 μm. Among the three methods for CCT measurement US pachymetry had the best agreement with the SL-OCT; the mean difference was the smallest (Table 2). Conversely, the comparison between US pachymetry and specular microscopy measurements had the least agreement; the mean difference was the largest (Table 2). Correlations (r2) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r2=0.98, P<0.0001) (Figure 4), specular microscopy (r2=0.98, P<0.0001) (Figure 5), and Orbscan (r2=0.96, P<0.0001) (Figure 6). Measurements by the various modalities were strongly correlated. Intra-class correlations of CCT, as measured by US pachymetry when compared with the other modalities, conveyed a strong and positive intra-class correlation coefficient (ICC =0.95).


Comparison of central corneal thickness: ultrasound pachymetry versus slit-lamp optical coherence tomography, specular microscopy, and Orbscan.

Khaja WA, Grover S, Kelmenson AT, Ferguson LR, Sambhav K, Chalam KV - Clin Ophthalmol (2015)

Scatter plot display of ultrasound pachymetry with specular microscopy measurement of CCT (r2=0.98).Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4472076&req=5

f5-opth-9-1065: Scatter plot display of ultrasound pachymetry with specular microscopy measurement of CCT (r2=0.98).Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness.
Mentions: The Bland–Altman plot showed that the measurements acquired via US pachymetry were greater than those obtained by SL-OCT for mean CCT values from 475–550 μm (Figure 1). For CCT values beyond 550 μm SL-OCT measurements were higher than US pachymetry. The mean (± SD) CCT measurement difference between the two methods was 1.24 (±4.51) μm, and the 95% limits of agreement (LOA) were between −21.76 and 18.18 μm. US pachymetry measurements when compared to specular microscopy, showed an overall decrease in measurement values for CCT when values ranged from 500 to 650 μm (Figure 2). In this case mean (±SD) difference was 8.69 (±1.24) μm while the 95% LOA range was −8.82 to 27.4 μm (Figure 2). Bland–Altman plot comparison of CCT measurements obtained by US pachymetry vs Orbscan II (Figure 3) demonstrated that US pachymetry showed little relative difference in CCT measurements within the range of 500–650 μm as compared to Orbscan. Table 2 shows that the mean (±SD) difference between US pachymetry and Orbscan II was 2.8 (±0.28) μm with a 95% LOA range between −30.15 and 24.40 μm. Among the three methods for CCT measurement US pachymetry had the best agreement with the SL-OCT; the mean difference was the smallest (Table 2). Conversely, the comparison between US pachymetry and specular microscopy measurements had the least agreement; the mean difference was the largest (Table 2). Correlations (r2) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r2=0.98, P<0.0001) (Figure 4), specular microscopy (r2=0.98, P<0.0001) (Figure 5), and Orbscan (r2=0.96, P<0.0001) (Figure 6). Measurements by the various modalities were strongly correlated. Intra-class correlations of CCT, as measured by US pachymetry when compared with the other modalities, conveyed a strong and positive intra-class correlation coefficient (ICC =0.95).

Bottom Line: Correlations (r (2)) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r (2)=0.98, P<0.0001), specular microscopy (r (2)=0.98, P<0.0001), and Orbscan (r (2)=0.96, P<0.0001).All modalities had a linear correlation with US pachymetry measurements.The four modalities showed significant linear correlations with one another.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, University of Florida, College of Medicine, Jacksonville, FL, USA.

ABSTRACT

Background: Central corneal thickness (CCT) can be measured by using contact and non-contact methods. Ultrasound pachymetry (US pachymetry) is a contact method for measuring CCT and is perhaps the most commonly used method. However, non-contact methods like scanning slit topography (Orbscan II), slit-lamp optical coherence tomography (SL-OCT), and specular microscopy are also used. Not many studies have correlated the measurement of CCT with all four modalities. The purpose of this study was to compare and correlate the CCT measurements obtained by US pachymetry with SL-OCT, specular microscopy, and Orbscan.

Method: This is a prospective, comparative study done in an institutional setting. Thirty-two eyes of 32 subjects with no known ocular disease and best-corrected visual acuity of 20/20 were enrolled. CCT measurements were obtained using SL-OCT, specular microscopy, scanning slit topography (Orbscan), and US pachymetry. Three measurements were made with each instrument by the same operator. Mean, standard deviation, and coefficient of variation were calculated for CCT measurements acquired by the four measurement devices. Bland-Altman plot was constructed to determine the agreements between the CCT measurements obtained by different equipment.

Results: The mean CCT was 548.16±48.68 μm by US pachymetry. In comparison, CCT averaged 546.36±44.17 μm by SL-OCT, 557.61±49.92 μm by specular microscopy, and 551.03±48.96 μm by Orbscan for all subjects. Measurements by the various modalities were strongly correlated. Correlations (r (2)) of CCT, as measured by US pachymetry compared with other modalities, were: SL-OCT (r (2)=0.98, P<0.0001), specular microscopy (r (2)=0.98, P<0.0001), and Orbscan (r (2)=0.96, P<0.0001). All modalities had a linear correlation with US pachymetry measurements.

Conclusion: In subjects with healthy corneas, SL-OCT, specular microscopy, and Orbscan (with correction factor) can be used interchangeably with US pachymetry in certain clinical settings. The four modalities showed significant linear correlations with one another.

No MeSH data available.


Related in: MedlinePlus