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

Figures & data

Table 1 Demographics of the subjects included in the study

Number of subjects	32
Number by race (%)
Caucasian	19 (59%)
African	5 (16%)
Asian	7 (22%)
Hispanic	1 (3%)
Mean/median age (years)	31.2/32
Age range (years)	19–54
Sex ratio (male:female)	15:17
Mean/median refraction	−1.52/−2.00 diopter

Table 2 Descriptive statistics for the central corneal thickness, as measured by the four different modalities

	US pachymetry	SL-OCT	Specular microscopy	Orbscan*
Mean CCT (μm)	548.16	546.36	557.61	551.03
Standard deviation (SD)	48.68	44.17	49.92	48.96
P-value (paired)	–	0.88	0.45	0.81
Mean (SD) CCT difference** (μm)	–	1.24 (±4.51)	8.69 (±1.24)	2.87 (±0.28)
Minimum	471.00	469.00	453.00	460.00
Maximum	656.00	631.00	686.00	672.00
Median	543.00	546.5	550.00	549.5

Notes:

* With acoustic correction factor of 0.92.

** Mean CCT difference as compared to US pachymetry.

Abbreviations: US pachymetry, ultrasound pachymetry; SL-OCT, slit-lamp optical coherence tomography; CCT, central corneal thickness.

Figure 1 Bland–Altman plot with 95% limits of agreement (LOA) illustrates the difference in central corneal thickness measurements (y-axis) between values obtained by ultrasound pachymetry vs values obtained by slit-lamp optical coherence tomography (SL-OCT) against the average CCT measurements of the two methods (x-axis).

Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness; vs, versus.

Figure 2 Bland–Altman plot with 95% limits of agreement (LOA) illustrates the difference in central corneal thickness measurements (y-axis) between values obtained by specular microscopy vs values obtained by ultrasound pachymetry against the average CCT measurements of the two methods (x-axis).

Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness; vs, versus.

Figure 3 Bland–Altman plot with 95% limits of agreement (LOA) illustrates the difference in central corneal thickness measurements (y-axis) between values obtained by ultrasound pachymetry vs values obtained by Orbscan against the average CCT measurements of the two methods (x-axis).

Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness; vs, versus; SL-OCT, slit-lamp optical coherence tomography.

Figure 4 Scatter plot display of ultrasound pachymetry with SL-OCT measurement of CCT (r²=0.982).

Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness; SL-OCT, slit-lamp optical coherence tomography.

Figure 5 Scatter plot display of ultrasound pachymetry with specular microscopy measurement of CCT (r²=0.98).

Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness.

Figure 6 Scatter plot display of ultrasound pachymetry with Orbscan measurement of CCT (r²=0.96).

Abbreviations: US pachymetry, ultrasound pachymetry; CCT, central corneal thickness.