Central corneal thickness and anterior chamber depth measurement by Sirius^® Scheimpflug tomography and ultrasound

Figures & data

Figure 1 Image of anterior segment obtained with the Sirius^® Scheimpflug device.

Abbreviations: ACD, anterior chamber depth; CCT, central corneal thickness.

Figure 2 Bland-Altman analysis of CCT values measured by ultrasound and Sirius^®. Abbreviation: CCT, central corneal thickness.

Figure 3 Bland-Altman analysis of ACD values measured with ultrasound biometry and Sirius^® device.

Abbreviation: ACD, anterior chamber depth.

Table 1 Average values and standard deviation for central corneal thickness and anterior chamber depth measurements obtained with the ultrasound devices and Sirius^® for three runs of measurements

n = 50	Central corneal thickness		Anterior chamber depth
Measure	Sirius (mean ± SD) (μm)	SP100 (mean ± SD) (μm)	Sirius (mean ± SD) (mm)	US800 (mean ± SD) (mm)
1	546.5 ± 39.43	540.6 ± 34.46	2.95 ± 0.33	3.37 ± 0.30
2	545.4 ± 38.46	541.4 ± 36.07	2.97 ± 0.31	3.37 ± 0.32
3	545.5 ± 38.63	542.0 ± 35.01	2.96 ± 0.30	3.34 ± 0.30
P	0.987*	0.980*	0.852**	0.964*

Notes:P, statistical significance for differences among the three test runs as obtained using

* analysis of variance test;

** Kruskal-Wallis test.

Abbreviation: SD, standard deviation.

Table 2 Average values, standard deviation, and range for central corneal thickness and anterior chamber depth measurements obtained with ultrasound and the Sirius^®

	n = 50	Mean	SD	Maximum	Minimum
Central corneal thickness (μm)	SP100	541.3	35.04	596.7	459.3
	Sirius	546.0	38.53	614.0	456.7
Anterior chamber depth (mm)	US800	3.36	0.29	4.16	2.89
	Sirius	2.96	0.30	3.59	2.26

Abbreviation: SD, standard deviation.

Figure 4 Bland-Altman analysis of ACD values measured with ultrasound biometry and Sirius^® device by adding the value of CCT to the Sirius ACD value.

Abbreviations: ACD, anterior chamber depth; CCT, central corneal thickness.

Figure 5 Bland-Altman analysis of ACD values measured with ultrasound biometry subtracting the value of CCT from the ultrasound biometric measure and Sirius^® device.

Abbreviations: ACD, anterior chamber depth; CCT, central corneal thickness.

Table 3 Mean difference, standard deviation, level of statistical significance, and limits of agreement between each set of measurement techniques to be compared at the 95% confidence interval

	Mean	SD	P	Limits of agreement
				Mean difference −1.96*SD	Mean difference +1.96*SD
CCT (μm)
Sirius versus SP100	4.68	10.47	0.003	−15.84	25.20
ACD (mm)
Sirius versus US800	−0.40	0.16	<0.001	−0.72	−0.07
Sirius + CCT* versus US800	0.15	0.16	<0.001	−0.16	0.45
Sirius versus US800 – CCT**	0.15	0.16	<0.001	−0.16	0.45

Notes:

* Sirius + CCT represents the sum of ACD and CCT obtained with Sirius;

** US800 – CCT represents the value of ACD obtained with US800 ultrasound biometry minus the CCT obtained with ultrasound pachymetry.

Abbreviations: ACD, anterior chamber depth; CCT, central corneal thickness; SD, standard deviation.