Randomized, masked, in vitro comparison of three commercially available tear film osmometers

Figures & data

Figure 1 Device A osmometer readings vs ideal dilution osmolarity.

Note: Wescor 5520 Vapro Pressure Osmometer: device A.

Figure 2 Device B osmometer readings vs ideal dilution osmolarity.

Note: TearLab Osmolarity System: device B.

Figure 3 Device C osmometer readings vs ideal dilution osmolarity.

Note: i-Med Pharma i-Pen: device C.

Figure 4 Device B and device C osmometers vs device A measured osmolarity.

Note: Wescor 5520 Vapro Pressure Osmometer: device A; TearLab Osmolarity System: device B; and i-Med Pharma i-Pen: device C.

Table 1 Combined osmolarity data on contrived tear solutions for device A, device B, and device C osmometers

Level	Device A	Device B	Device C
Measured osmolarity mean (mOsm/L)
1 (297)	305.6	300.6	336.4
2 (342)	352.2	341.4	342.0
3 (383)	389.8	376.8	345.7
Standard deviation (mOsm/L)
1	4.0	3.7	21.5
2	5.5	7.9	20.7
3	4.0	5.1	22.0
Coefficient of variation (%)
1	1.3	1.2	6.4
2	1.6	2.3	6.1
3	1.0	1.4	6.4

Note: Wescor 5520 Vapro Pressure Osmometer: device A; TearLab Osmolarity System: device B; and i-Med Pharma i-Pen: device C.

Figure 5 Bland–Altman plot for device B.

Note: TearLab Osmolarity System: device B.

Figure 6 Bland–Altman plot for device C.

Note: i-Med Pharma i-Pen: device C.

Figure 7 Distribution of deviation from ideal osmolarity values.

Note: TearLab Osmolarity System: device B; and i-Med Pharma i-Pen: device C.