Clinical application of the Swiss Liquid Jet Aesthesiometer for corneal sensitivity measurement

Figures & data

Figure 1. Diagram of the Swiss Liquid Jet Corneal Sensitivity Aesthesiometer (SLACS).

Table 1. Descriptive data for overall corneal sensitivity threshold measurements with SLACS and CB: medians/interquartile ranges.

	SLACS		CB
	mbar	dB	µN	dB
overall	339/217–502	25.3/23.4–27.0	86/57–135	19.3/17.5–21.3
Group A	263/197–415	24.2/22.9–26.2	86/57–135	19.3/17.5–21.3
Group B	431/268–567	26.3/24.3–27.5	86/86–135	19.3/19.3–21.3

Table 2. Descriptive data for individual corneal sensitivity threshold measurements with SLACS and CB: medians/interquartile ranges.

	SLACS
	Measurement 1		Measurement 2		Measurement 3		Measurement 4
	mbar	dB	mbar	dB	mbar	dB	mbar	dB
Overall	358/224–516	25.5/23.5–27.1	321/217–462	25.1/23.4–26.6	337/223–464	25.3/23.5–26.7	339/208–522	25.3/23.2–27.2
Group A	262/190–402	24.2/22.8–26.0	265/207–406	24.2/23.2–26.1	260/187–413	24.1/22.7–26.2	267/199–451	24.3/23–26.5
Group B	452/293–584	26.5/24.7–27.7	405/238–607	26.1/23.8–27.8	386/298–521	25.9/24.7–27.2	460/223–562	26.6/23.5–27.5
	CB
	Measurement 1		Measurement 2		Measurement 3		Measurement 4
	mN	dB	mN	dB	mN	dB	mN	dB
Overall	86/66.5–135	19.3/18.2–21.3	86/57–135	19.3/17.5–21.3	86/67–156	19.3/18.2–21.9	86/81.7–168	19.3/19.1–22.2
Group A	86/57–106	19.3/17.5–20.3	86/57–134	19.3/17.5–21.3	86/57–152	19.3/17.5–21.8	86/57–152	19.3/17.5–21.8
Group B	86/86–135	19.3/19.3–21.3	86/63–135	19.3/18.0–21.3	86/86–159	19.3/19.3–22.0	106/86–168	20.3/19.3–22.2

Figure 2. Bland Altman with bootstrap limits of agreement plots showing within visit (to the left) and between visit repeatability (to the right) for SLACS: bold lines for means; thin lines for 95% confidence intervals of the means; dotted lines for the lower and upper limits of CoR with their 95% confidence intervals.

Figure 3. Bland Altman with bootstrap limits of agreement plots showing within visit (to the left) and between visit repeatability (to the right) for CB: bold lines for means; dotted lines for the lower and upper limits of CoR with their 95% confidence intervals.

Table 3. Bland Altman analysis for the differences in measurements [dB] within and between visits (type) for groups A and B, as well as for the overall group: mean [CI], CoR [CI], lower limit [CI] and upper limit [CI].

Method	Type	Age group	Mean [CI]	CoR [CI]	Lower limit [CI]	Upper limit [CI]
SLACS	within	both	−0.01 [−0.19, 0.22]	2.56 [2.25, 2.70]	−2.78 [−2.97, − 0.32]	2.32 [1.85, 2.57]
SLACS	between	both	−0.02 [−0.24, 0.20]	3.61 [3.07, 4.14]	−3.75 [−4.24, −2.78]	3.46 [2.81, 4.53]
SLACS	within	A	0.19 [−0.06, 0.48]	2.47 [1.90, 2,63]	−2.75 [−2.94, −1.89]	2.19 [1.60, 2.42]
SLACS	between	A	0.03 [−0.24, 0.37]	3.09 [2.16, 3.99]	−3.29 [−3.78, −2.07]	2.83 [1.55, 4.57]
SLACS	within	B	−0.22 [−0.62, 0.07]	2.56 [2.15, 3.29]	−2.75 [−3.32, −2.15]	2.37 [1.75, 3.68]
SLACS	between	B	−0.10 [−0.49, 0.24]	3.96 [3.05, 4.45]	−4.18 [−4.36, −2.64]	3.75 [2.74, 4.66]
CB	within	both	0.00 [0.00, 0.00]	2.27 [1.99, 3.09]	−2.03 [−2.19, −1.99]	2.47 [1.99, 4.12]
CB	between	both	0.00 [0.00, 0.00]	4.42 [3.65, 6.06]	−3.88 [−6.60, −2.21]	4.97 [4.72, 6.70]
CB	within	A	0.00 [0.00, 0.00]	2.01 [1.59, 2.30]	−1.99 [−2.54, −1.63]	2.03 [1.22, 2.35]
CB	between	A	0.00 [0.00, 0.00]	4.68 [3.42, 5.66]	−3.14 [−4.91, −1.95]	6.17 [4.50, 6.73]
CB	within	B	0.00 [0.00, 0.00]	2.37 [2.02, 3.77]	−2.05 [−2.25, −1.99]	2.68 [1.99, 5.48]
CB	between	B	0.08 [0.00, 0.91]	4.78 [3.35, 7.45]	−4.84 [−8.98, −1.99]	4.72 [3.79, 7.82]
CB	within	B	0.01 [0.00, 0.00]	3.09 [2.09, 3.80]	−2.06 [−2.27, −1.99]	4.12 [2.12, 5.55]
CB	between	B	0.07 [0.00, 0.92	4.03 [2.49, 6.04]	−3.20 [−4.97, −1.99]	4.86 [2.92, 8.23]

Figure 4. Estimated median values and Hodge Lehman 95% confidence intervals for corneal sensory thresholds for SLACS and CB for the overall group for all four measurements separately, obtained with a bootstrap method.

Figure 5. Correlation between SLACS and CB for sensory thresholds for the overall subject group.

Figure 6. Correlations between SLACS and CB for sensory thresholds for Group A and B separately.