Accuracy Analysis Of Non-contact Tonometer And Rebound Tonometer In Glaucoma Patients

Objective: Glaucoma is the world’s number one irreversible blinding eye disease.At present,the most effective and definite treatment method is to control the increasing pathological intraocular pressure.Therefore,accurate intraocular pressure measurement results are very important in clinical diagnosis and treatment.This study compares the consistency and accuracy of two tonometers(NCT and RBT)with the gold standard method(GAT)in glaucoma patients.Meanwhile discussed the advantages and disadvantages of the three tonometers,and analyze their clinical applicability,to guide the rational application of the clinical tonometer.Methods: This study was a retrospective study.A total of 185 eyes of 113 glaucoma patients were included.During the two periods of 9:00-9:30 and 16:00-16:30,the intraocular pressure was measured in the sitting position for two times respectively,and a total of 370 sets of intraocular pressure measurement data were collected,with the order of RBT,NCT and GAT.Wilcoxon paired rank sum test,Spearman rank correlation,and ISO 8612-2009 were used to evaluate the accuracy of NCT’s and RBT’s measurements.Bland-Altman consistency analysis charts were used to analyze the consistency between NCT,RBT and GAT in the normal IOP group(10~21mmHg),the abnormal IOP group(> 21 mmHg or < 10mmHg)and the whole IOP group,respectively.Result: A total of 185 eyes of 113 patients with glaucoma were included in this study.A total of 370 groups of IOP measurement data were obtained.The GAT measurement range is 7 to 42 mmHg,?x ± s is 17.36 ± 5.41 mmHg,and the median is 17 mmHg.The NCT measurement range is 6.8 to 49.8 mmHg,?x ± s is 17.26 ± 5.91 mmHg,and the median is 16.20 mmHg.The RBT measurements range is 8.4 to 39 mmHg,?x ± s is 18.51 ± 4.74 mmHg,and the median is 18.20 mmHg.The IOP reading by NCT was lower than GTA,but there was no significant difference(P = 0.92);The IOP reading by RBT was higher than GTA,and there was a significant statistical difference(P <0.05).Spearman rank correlation analysis showed that in glaucoma patients,NCT and RBT measurements showed significant positive correlation with GAT measurements,with correlation coefficients r=0.77 and r=0.71 respectively.The regression equations of intraocular pressure in the two groups were: GAT=1.06+0.93×NCT,GAT=6.34+0.70×RBT.The regression equations in both groups were statistically significant(P < 0.05).Bland-Altman consistency analysis shows that the average deviation between GAT and NCT measurement results is only-0.1mmHg,and the 95% LoA is-6.2 ~ 6.0 mmHg,3.24% of the measured values were outside the bounds,and the absolute value of the maximum difference between the two was 6mmHg.The average deviation between GAT and RBT measurement results is 1.2 mmHg,and the 95% LoA is-5.2 to 7.6 mmHg,3.24% of the measurements were outside the bounds,and the absolute value of the maximum difference between the two was 7.4 mmHg.In the normal intraocular pressure group,the measurement result deviation between GAT and NCT is 0,and the 95% LoA is-5.9 ~ 5.9mmHg,2.4% of the measured values were outside the bounds,and the absolute value of the maximum difference between the two was 5.8 mmHg.The average deviation between GAT and RBT measurement results is 1.6 mmHg,and 95% LoA is-4.3 to 7.5 mmHg,3.78% of the measured values are outside the limit range,and the absolute value of the maximum difference between the two is 7.4 mmHg In the abnormal IOP group,the average deviation between GAT and NCT was-0.5 mmHg,and the 95% LoA was-7.3 to 6.4 mmHg,2.53% of the measured values exceeded the limit range,and the absolute value of the maximum difference between the two was 7.2 mmHg.The average deviation between GAT and RBT measurement results is-1.0 mmHg,and the 95% LoA is-7.5 ~ 5.6mmHg,3.8% of the measured values are outside the limit,and the absolute value of the maximum difference between the two is 7 mmHg.The measurement quality of NCT and RBT was evaluated according to ISO 8612-2009,and the results showed that the percentage of data with the measured value of NCT and RBT exceeding the measured value of GAT ± 5mmHg was(3.9%,11.3%,12.2%)and(26.3%,11.3%,12.2%),respectively,which exceeded the error within 5% allowed by international standards.Conclusion:1.There is a good correlation and consistency between the measurement results of NCT,RBT and GAT in glaucoma patients,but the measurement error is too large to be accepted by the clinic,so NCT and RBT cannot simply replace GAT.2.In glaucoma patients,even the intraocular pressure within the normal range,there still a significant error between the measurement results of NCT and RBT and GAT.3.Among the three tonometers,RBT has the highest success rate.The objectivity of NCT measurement was the strongest,but the requirements for ocular surface condition were the highest.The clinician should use the tonometer reasonably as needed.