Agreement Repeatability

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Agreement Repeatability

As the stability of the tear film may be affected by fluorescein, the Dry Eye Workshop (DEWSII) recommended non-invasive measurement of tear breakage time (NIBUT). The objective of this study was to examine the consistency and repeatability of four different instruments when measuring the NIBUT. The comparison between TonoVet and Tono-Pen and the manometric method of IOP in rabbits was previously studied8,11,12,13,14,15,16. Lim et al. reported that Tono-Pen underestimates the IOP itself and that it has no error at high levels of IOP, but it has been found to be the most accurate tonometer among tono-pen, perkins and pneumatonometer11. Acosta et al. found that the tono-pen rabbit underestimated IOP in all printing areas from 5 to 50, and the low forecast was more remarkable at high pressure8. Zhang et al. reported that TonoVet tended to display IOP values consistently lower than those of gauges in all printing areas, whether they use a type of calibration “d” (dogs or cats) or “p” (other species). Consistent with previous studies, our results showed that TonoVet and Tono-Pen consistently underestimated the actual IOP up to 5 mmHg for the Tono pen and that underestimation increased with the increase in IOP. The increasing inaccuracy can be attributed to the measurement error, which is increased as the pressure increases for both devices.

Kalesnykas et al. reported that Tono-Pen overestimated the IOP at a reservoir pressure of no more than 10 mmHg, which is also underestimated by IOP12. The inconsistency can be explained by the fact that their data were based on a small sample size (n -2). If a method has poor repeatability, the agreement between the two methods will also be bad. If both methods have poor repeatability, the agreement will be even worse. If we compare the agreement with an old method with poor repeatability, even a perfect new method will not agree. Sample size was calculated for the study of the agreement using formula ≥ 21, where n, α and β are sample size, disordance rate and probability of tolerance (if α 0.15 and β 80%, n ≥ 10). The experiment was conducted under general anesthesia with ketamine (30 mg/kg) and xylazine (5 mg/kg) intramuscularly. Two 25-track needles were inserted into the front chamber of the right eye by a self-sealed limbal cut in position 3 and 9 hours. One was connected by polyethylene pipes to a bottle filled with a balanced saline solution under an open tap, while the other was connected to a vertical water column to measure the IOP. The height of the symmetrical saline solution bottle has been vertically modified to reach different PMIs ranging from 60 to 5 mmHg x 5 mmHg 5 mmHg decrements of 5 mmHg, based on the reading of the water column.

If the reading of the water column reached a stable value for more than 2 minutes, four sets of IOP measurements were taken blindly with tonovet, then with a tono pen at each bottle height. The IOP values of the two tonometers at each pressure level were compared to the IOP itself to determine accuracy. Pearson`s linear correlation and regression analyses were used to determine a most appropriate line to assess variation in measurement errors. Bland-Altman Bias Plots22.23 were drawn to assess the degree of correspondence between the IOP values measured by the two tonometers and the gauge. An attribute analysis was developed to simultaneously assess the effects of repeatability and reproducibility on accuracy. It allows the analyst to review the responses of several reviewers if they look at multiple scenarios multiple times. It establishes statistics that assess the ability of evaluators to agree with themselves (repeatability), with each other (reproducibility) and with a master or correct value (overall accuracy) known for each characteristic – over and over again. [7] The repeatability coefficient is 42.4 for the Wright measuring device and 55.2 for the Mini Wright measuring device.