Reliability of the noncontact tonometer (Nidek NT-3000)

Abstract

Noncontact tonometer (NCT) is one of the commonly used methods for Intra ocular pressure (IOP) measurement. Its potential advantage is that it uses an air puff to indent the cornea, reducing the risk of cross infection, and does not require corneal anesthesia. Measurement errors of this instrument may be due to intraobserver and interobserver variability. There are few studies of the reliability of the NCT and none for the reliability of the Nidek NT-3000. In this study, we assessed the reliability of IOP measurements obtained with the Nidek NT-3000 noncontact tonometer (NCT). IOP was measured by Nidek NT-3000 in both eyes of 207 subjects. Two sets of IOPs were recorded from each subject with a ten minute interval between each set. The measurements of the right eye were performed by a single nurse for 2 sets. The measurements of the left eye were performed by 2 nurses for each set. The mean of three consecutive pulse recordings in each set was used for data analysis. The results of the study showed that the average age of the patients was 56.46 ± 14.18 years . The IOP range under study varied from 5.5-28.5 mmHg. The mean ± SD IOP measurements in the right eyes were 13.65 ± 3.13 and 13.54 ± 2.98 mmHg for the first and the second sets, respectively and in the left eyes were 13.25 ± 3.10 and 13.22 ± 3.09 mmHg for the first and the second sets, respectively. The mean difference ± SD (95% limit of agreement) between the two measurements in the right eye was 0.11 ± 1.10 mmHg and in the left eye was 0.04 ± 0.91 mmHg, In addition, there was no correlation between the differences of the values from the two sets or the average IOP of the two sets in both eyes. This study suggests that Nidek NT-3000 is a reliable instrument for IOP