Comparability analysis of the HNT-1P Huvitz non contact tonometer for the measurement of intraocular pressure.

PURPOSE: To evaluate the diagnostic validity of the HNT-1P non-contact tonometer (Huvitz) as a tool for accurately measuring intraocular pressure (IOP) in patients with healthy eyes, compared to the Goldmann applanation tonometer (GAT), which is the Gold Standard method for measurement of IOP. METHODS: Observational, descriptive, transversal study using 148 eyes of 74 healthy patients without a diagnosis of glaucoma or other ophthalmological diseases. Three measurements of IOP were taken in each eye, using three tonometers: HNT-1P, ICR100, and GAT. The median IOP (quartiles) and mean IOP (SD) its statistical significance were calculated, and comparisons were made between the mean and median IOP values found in three groups: GAT-HNT, GAT-ICR, and HNT-ICR. The difference in mean and median IOP was analyzed in each of the three study groups, and its statistical significance and concordance correlation coefficient (CCC) were calculated. RESULTS: The median IOP with HNT-1P was statistically significantly lower than the median IOP with GAT, (1.1 mmHg, p < 0.001). The median IOP with HNT-1P was also lower than the median IOP with ICR100. As an additional result, the median IOP with GAT was lower than the median IOP with ICR. The CCC was moderate for HNT-ICR (0.72) and low for GAT-HNT and GAT-ICR (0.43 and 0.38, respectively). CONCLUSIONS: HNT-1P (Huvitz) provides statistically significantly lower IOP values than those obtained with GAT. HNT-1P could be used for screening of ocular hypertension in postoperative patients. The IOP measurement obtained with HNT-1P should be confirmed with GAT. HNT-1P yields lower IOP values than those obtained with ICR.

Agreement of intraocular pressure measurement with Corvis ST, non-contact tonometer, and Goldmann applanation tonometer in children with ocular hypertension and related factors.

AIM: To access the agreement of intraocular pressure (IOP) values obtained from biomechanically corrected tonometer [Corvis ST (CST)], non-contact tonometer (NCT), and Goldmann applanation tonometer (GAT) in children with NCT measured-IOP (NCT-IOP) values of 22 mm Hg or more, and related factors. METHODS: A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST, NCT, and GAT. Based on GAT measured IOP (GAT-IOP), ocular hypertension (OHT) group (≥22 mm Hg, 24 eyes) and the non-OHT group (<22 mm Hg, 27 eyes) were defined. We compared the agreement of the three measurements, i.e., CST measured IOP (CST-IOP), GAT-IOP, and NCT-IOP, and further analyzed the correlation between the differences in tonometry readings, central corneal thickness (CCT), axial length (AL), optic disc rim volume, and age. RESULTS: Compared with the OHT group, thicker CCT, larger rim volume, and higher differences between NCT-IOP and GAT-IOP, were found in the non-OHT group. The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups. The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg (95% limit of agreement ranged from 0.1 to 2.41 mm Hg, OHT group) and 1.20 mm Hg (95% limit of agreement ranged from -0.5 to 3.00 mm Hg, non-OHT group), and the mean differences in NCT and GAT were 3.90 mm Hg (95% limit of agreement ranged from -0.19 to 9.70 mm Hg, OHT group) and 6.00 mm Hg (95% limit of agreement ranged from 1.50 to 10.50 mm Hg, non-OHT group). The differences between CST-IOP and GAT-IOP were not related to CCT, age, and AL in both groups; while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group (r=0.93, P<0.001) and to CCT and AL in the non-OHT group (r=0.66, P<0.001, r=-0.81, P<0.001). CONCLUSION: The accuracy of NCT in the diagnosis of pediatric OHT is low. The agreement of CST-IOP and GAT-IOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP. Therefore, CST can be used as a good alternative for IOP measurement in children. The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.

Assessment of intraocular pressure measurement between Goldman applanation tonometer, rebound tonometer, non-contact tonometer, and its correlation with central corneal thickness.

Purpose: To compare readings of intraocular pressure (IOP) taken with the Goldmann applanation tonometer (GAT), the non-contact tonometer (NCT), and the rebound tonometer (RBT), and to compare their correlation with central corneal thickness (CCT). Methods: This was a prospective, cross-sectional, observational study to which patients above 18 years of age were enrolled. A total of 400 eyes of 200 non-glaucomatous patients underwent IOP recordings using the GAT, NCT, and RBT, and CCT was also noted. Informed consent of the patients was taken. The IOP readings taken via the three methods were compared and correlated with CCT. Paired t test was used to compare the two devices. Simple and multivariate linear regression analyses were used to study the relationship between factors. A P value less than 0.05 was considered significant. Correlation was determined using the Pearson correlation coefficient, and a Bland-Altman graph was plotted. Results: Mean IOP measured by the NCT was 15.65 ± 2.80 mmHg, by the RBT was 14.23 ± 3.05 mmHg, and by the GAT was 14.69 ± 2.97 mmHg. The mean CCT was 510.61 ± 33.83 microns. The difference between mean IOP recorded by the NCT and that by the RBT was 1.41 ± 2.39 mmHg, between the NCT and GAT was 0.95 ± 2.03 mmHg, and between the GAT and RBT was 0.45 ± 2.22 mmHg. The difference between the IOP values was statistically significant (P < 0.005). All tonometers showed a statistically significant correlation with CCT, but it was observed that the NCT had a stronger correlation (0.4037). Conclusion: The IOP readings taken by all the three methods were comparable; however, RBT values were closer to GAT values. CCT did influence the IOP values, and this should be kept in mind while evaluating.

Comparison of Icare HOME and non-contact tonometer in intraocular pressure measurement in the early stage after ICL V4c implantation.

PURPOSE: To investigate the characteristics of intraocular pressure (IOP) measurements using the Icare HOME rebound tonometer (RBT) and non-contact tonometer (NCT) during the early stage after implantable collamer lens (ICL) V4c implantation, and to assess the agreement between the two methods. METHODS: This prospective case series study included 104 eyes of 53 patients (mean age 28.77 ± 5.34 years), who underwent ICL V4c implantation. IOP was measured preoperatively, and at 0.5, 1, 2, 4, and 24 h postoperatively by Icare HOME and NCT, respectively. RESULTS: All surgeries were uneventful. IOP measurements by Icare and NCT preoperatively were 14.03 ± 2.90 mmHg and 14.09 ± 2.87 mmHg, respectively.The corresponding values were 12.56 ± 8.09 mmHg and 14.12 ± 6.52 mmHg (P > 0.05) at postoperative 0.5 h, 19.21 ± 8.74 mmHg and 19.60 ± 7.66 mmHg at postoperative 1 h (P > 0.05), 21.21 ± 8.10 mmHg and 20.31 ± 6.93 mmHg at postoperative 2 h (P > 0.05), 16.11 ± 5.89 mmHg and 17.04 ± 4.84 mmHg at postoperative 4 h (P > 0.05), and 14.04 ± 3.88 mmHg and 14.78 ± 2.80 mmHg at postoperative 24 h, respectively (P > 0.05). There was good agreement based on intraclass correlation coefficients (ICCs) between NCT and Icare HOME (all ICCs > 0.6 at different time points [range, 0.6986-0.956]). The Bland-Altman plot showed a mean percentage of over 95.81% of the points falling within the limits of agreement. There was a significant difference in the low IOP measurements (<10 mmHg) between Icare HOME and NCT (7.28 ± 2.55 vs. 10.65 ± 2.48, P < 0.001). CONCLUSION: Icare HOME can be used for IOP measurement after ICL V4c implantation and demonstrated good agreement with NCT, except in cases with low intraocular pressure (<10 mmHg).

Assessment of temporal and spatial distribution patterns of aerosol produced by air-puff non-contact tonometer.

PURPOSE: To assess the distribution pattern of aerosol in the aspect of time and direction during the intraocular pressure (IOP) measurement by air-puff non-contact tonometer (NCT) and further offer references for protection from coronavirus disease-19 (COVID-19) in the routine ophthalmic examination. METHOD: A single-center observational study was conducted in the ophthalmology clinics of Peking University Third Hospital. Two air quality detectors were equipped to assess the generated particulate matter (PM) concentration simultaneously within 30 s after IOP measurement in the outpatient hall. Detector A was fixed next to the NCT as a reference, while Detector B was fixed 1 meter away. The participants were divided into two groups depending on the position of Detector B. The generation of aerosol was compared within different groups and time intervals. RESULTS: 144 participants were enrolled in the final analysis. At a 1 m distance from the NCT, the PM2.5 concentration significantly increased at the 30 s (Z = 2.898, Bonferroni-corrected P = 0.038) while the PM10 concentration increased immediately after the IOP measurement (Z = 2.967, Bonferroni-corrected P = 0.030). The PM2.5 and PM10 concentrations at 1 m were significantly higher immediately (Z = -2.183, P = 0.029; Z = -2.502, P = 0.012) and 30 s (Z = -2.021, P = 0.043; Z = -2.071, P = 0.038) after the IOP measurements when the Detector B was vertical to the air jet on the lateral side. CONCLUSIONS: NCT may produce aerosol after the IOP measurement by air-puff. The generated PM2.5 had a prolonged existence compared with PM10 at a 1 m distance. The lateral side of the air-puff direction may be of higher exposure risk to aerosol.

A new method for the in vivo identification of degenerated material property ranges of the human eye: feasibility analysis based on synthetic data.

This paper proposes a new method for in vivo and almost real-time identification of biomechanical properties of the human cornea based on non-contact tonometer data. Further goal is to demonstrate the method's functionality based on synthetic data serving as reference. For this purpose, a finite element model of the human eye is constructed to synthetically generate full-field displacements from different data sets with keratoconus-like degradations. Then, a new approach based on the equilibrium gap method combined with a mechanical morphing approach is proposed and used to identify the material parameters from virtual test data sets. In a further step, random absolute noise is added to the virtual test data to investigate the sensitivity of the new approach to noise. As a result, the proposed method shows a relevant accuracy in identifying material parameters based on full-field displacements. At the same time, the method turns out to work almost in real time (order of a few minutes on a regular workstation) and is thus much faster than inverse problems solved by typical forward approaches. On the other hand, the method shows a noticeable sensitivity to rather small noise amplitudes rendering the method not accurate enough for the precise identification of individual parameter values. However, analysis show that the accuracy is sufficient for the identification of property ranges which might be related to diseased tissues. Thereby, the proposed approach turns out promising with view to diagnostic purposes.

Different Effects of Aging on Intraocular Pressures Measured by Three Different Tonometers.

This study aimed to compare intraocular pressures (IOP) using different tonometers, Goldmann applanation (IOPGAT), non-contact (IOPNCT), and rebound (IOPRBT), and to assess the effects of aging and central corneal thickness (CCT) on the measurements. The IOPGAT, IOPNCT, IOPRBT, mean patient age (65.1 ± 16.2 years), and CCT (521.7 ± 39.2 µm) were collected retrospectively from 1054 eyes. The differences among IOPs were compared by the paired t-test. Possible correlations between devices, age, and CCT were assessed by linear regression analyses. The effects of age and CCT on the IOP reading were assessed by mixed-effects regression models. The IOPGAT values were 2.4 and 1.4 mmHg higher than IOPNCT and IOPRBT, respectively; the IOPNCT was 1.0 mmHg lower than IOPRBT (p < 0.0001 for all comparisons). The IOPs measured by each tonometer were highly correlated with each other (r = 0.81-0.90, t = 45.2-65.5). The linear regression analyses showed that age was negatively correlated with IOPNCT (r = -0.12, t = -4.0) and IOPRBT (r = -0.14, t = -4.5) but not IOPGAT (r = 0.00, t = -0.2); the CCT was positively correlated with IOPGAT (r = 0.13, t = 4.3), IOPNCT (r = 0.29, t = 9.8), and IOPRBT (r = 0.22, t = 7.2). The mixed-effect regression models showed significant negative correlations between age and IOPNCT (t = -2.6) and IOPRBT (t = -3.4), no correlation between age and IOPGAT (t = 0.2), and a significant positive correlation between CCT and the tonometers (t = 3.4-7.3). No differences between IOPGAT and IOPRBT were seen at the age of 38.8 years. CCT affects IOPs from all tonometers; age affects IOPNCT and IOPRBT in different degrees. IOPRBT tended to be higher than IOPGAT in young subjects, but this stabilized in middle age and became higher in older subjects.

Ocular biometric parameters are associated with non-contact tonometry measured intraocular pressure in non-pathologic myopic patients.

PURPOSES: This research aimed to investigate effects and risk factors on non-contact tonometer (NCT) readings in healthy myopic subjects by employing cross-sectional study design. METHODS: Totally, sixty otherwise healthy myopic volunteers (mean 28.4 years old) with 90% female were recruited in ophthalmic clinic. The routine ophthalmic tests, refractive evaluation, examination central corneal thickness (CCT), depth of anterior chamber, axial length, corneal curvature, white-to-white and NCT were assessed at baseline. The linear-mixed model was utilized to evaluate correlation between the readings and ocular biometric parameters. RESULTS: For population in this study, mean spherical equivalents were - 4.85 ± 1.79 diopters in right eyes and - 4.63 ± 1.95 diopters in left eyes. Meanwhile, 28.3% of the eyes had a refractive error exceeding - 6.0 diopters. The mean NCT reading was 15.02 ± 3.02 mmHg in left eyes and 15.33 ± 2.96 mmHg in right eyes. Among the factors analyzed, CCT was the most significant parameter associated with NCT readings. After adjusting for the other factors, per one standard deviation increase of central corneal thickness (36.11 µm) was associated a 1.14 (95% confidence interval 0.53-1.77) mmHg elevated NCT reading. The average central corneal curvature, age and spherical equivalence were also significantly and independently associated with NCT readings. CONCLUSIONS: Central corneal thickness, age, corneal curvature and degree of myopia were independently associated with NCT measured intraocular pressure. Central corneal thickness is one of the most influential factors.

The Association of Central Corneal Thickness and Intraocular Pressure Measures by Non-Contact Tonometry and Goldmann Applanation Tonometry among Glaucoma Patients.

BACKGROUND: The aim of this study was to determine whether Central Corneal Thickness (CCT) is associated with intraocular pressure measurement (IOP) with a Non-contact tonometer and the Goldmann applanation tonometer in glaucoma patients. MATERIALS AND METHODS: The study involved two hundred and thirty-two eyes of clinically diagnosed glaucoma patients receiving care at a referral facility. IOP measurements were obtained using both the Non-Contact Tonometer (NCT) and Goldmann Applanation Tonometer (GAT). The association between age, ethnicity, and CCT, as well as CCT on the measures of NCT and GAT, were analyzed. RESULTS: There were 64(55.2%) males and 52 (44.8%) females and their ages ranged from 18 to 85 years (mean age = 47.72; SD ± 15.75 years). There was a weak positive correlation between the CCT and NCT findings in the right eye (r = 0.19, n = 116, p < 0.05) and in the left eye (r = 0.25, n = 116, p < 0.05). However, there was no correlation between CCT and GAT measurements. Age had a significant correlation with CCT while gender and ethnicity had no significant correlation. CONCLUSION: The study found a significant association between CCT and NCT. However, there was no significant association between CCT and GAT. CCT had an association with age but independent of gender and ethnicity since there was no significant relationship between these variables.

Comparability of three intraocular pressure measurement: iCare pro rebound, non-contact and Goldmann applanation tonometry in different IOP group.

BACKGROUND: Measurement of intraocular pressure (IOP) is essential for glaucoma patients. Many factors such as central corneal thickness (CCT) can affect the accuracy of IOP measurement. The purpose of this study was to evaluate the agreement of IOP measured by non-contact tonometer (NCT), iCare pro rebound tonometer (iCare), and Goldmann applanation tonometer (GAT) in different IOP group. METHODS: This was a Hospital-based cross-sectional study. Two hundred subjects were enrolled in this study. All subjects underwent IOP measurement using an NCT-iCare-GAT sequence. Bland-Altman, Pearson correlation and intraclass correlation analysis were performed using SPSS 17.0 software. The influence of CCT on each IOP measurement methods was evaluated by linear regression analysis. RESULTS: The mean difference (Δ) of NCT-GAT did not differ from (Δ) iCare-GAT in IOP < 10 and 10-21 mmHg group. However, (Δ) NCT-GAT was significantly higher than (Δ) iCare-GAT in IOP 22-30 and > 30 mmHg group (P < 0.05). Bland-Altman analysis showed significant agreement between the three devices (P < 0.01). IOP measurements of the three methods were significantly correlated with CCT (P < 0.01). CONCLUSIONS: ICare pro shows a higher agreement with GAT over a wide range of IOP compared with NCT. The consistency between the three tonometers was similar in a low and normal IOP range. However, NCT shows a greater overestimate of IOP in moderate and higher IOP group. The variability of IOP measurement affected by CCT is NCT > iCare pro > GAT.

Accuracy of intraocular pressure measurements between non-contact tonometer and ICare rebound tonometer / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To analyze the accuracy of non-contact tonometer(NCT)and ICare rebound tonometer(RBT)in measuring intraocular pressure in glaucoma patients. <p>METHODS:A retrospective proportional control study. Totally 113 patients(185 eyes)with glaucoma were studied. Intraocular pressure was measured by RBT, NCT and Goldmann Applanation tonometer(GAT)at 9:00 and 16:00 and recorded as two sets of data, respectively. Their accuracy is evaluated by the rank sum test, and the international standard 8621 guide, Bland-Altman consistency analysis analyzed the consistency of the two groups of measurements, and the data were divided into two groups: abnormal intraocular pressure group(<10mmHg or >21mmHg)and normal intraocular pressure group(10-21mmHg). The consistency was analyzed between different groups. The spearman correlation analysis is adopted to analyze the correlation between ophthalmotonometers.<p>RESULTS: There were differences among the GAT, NCT and RBT measurements(<i>P</i><0.01). There was a strong correlation between the intraocular pressure measured value obtained by GAT and measured values obtained by RBT and NCT(<i>rs</i>=0.71, 0.77, <i>P</i><0.001). The measured values of NCT and GAT are close to each other without statistically significant differences(<i>P</i>=0.92). Compared with GAT, RBT has a higher intraocular pressure measured value, and there are significant differences(<i>P</i><0.05). However, compared with GAT, both NCT and RBT have a wide range of limits of agreement, and they are(-6.2-6.0mmHg)and(-5.2-7.6mmHg)respectively. In normal intraocular pressure groups, the ranges of limits of agreement are(-5.9-5.9mmHg)and(-4.3-7.5mmHg)respectively. In abnormal intraocular pressure groups, the ranges of limits of agreement are(-7.3-6.4mmHg)and(-7.5-5.6mmHg)respectively. The evaluation carried out in accordance with ISO 8612 guides indicates that the abnormal values more than the 95% of consistency restriction of NCT and RBT in the three groups are(3.9%, 11.3%, 12.2%)and(26.3%, 11.3%, 12.2%)respectively.<p>CONCLUSION: Both NCT and RBT cannot simply replace the GAT to measure the intraocular pressure of glaucoma patients. In glaucoma patients, with the deviation of the measured value from the normal intraocular pressure range, the measurement error of NCT and RBT also increase.

Agreement among Goldmann applanation tonometer, iCare, and Icare PRO rebound tonometers; non-contact tonometer; and Tonopen XL in healthy elderly subjects.

PURPOSE: To evaluate the inter-device agreement among the Goldmann applanation tonometer (GAT), iCare and Icare PRO rebound tonometers, non-contact tonometer (NCT), and Tonopen XL tonometer. METHODS: Sixty healthy elderly subjects were enrolled. The intraocular pressure (IOP) in each subject's right eye was measured thrice using each of the five tonometers. Intra-device agreement was evaluated by calculating intraclass correlation coefficients (ICCs). Inter-device agreement was evaluated by ICC and Bland-Altman analyses. RESULTS: ICCs for intra-device agreement for each tonometer were >0.8. IOP as measured by iCare (mean ± SD, 11.6 ± 2.5 mmHg) was significantly lower (p < 0.05) than that measured by GAT (14.0 ± 2.8 mmHg), NCT (13.6 ± 2.5 mmHg), Tonopen XL (13.7 ± 4.1 mmHg), and Icare PRO (12.6 ± 2.2 mmHg; Bonferroni test). There was no significant difference in mean IOP among GAT, NCT, and Tonopen XL. Regarding inter-device agreement, ICC was lower between Tonopen XL and other tonometers (all ICCs < 0.4). However, ICCs of GAT, iCare, Icare PRO, and NCT showed good agreement (0.576-0.700). The Bland-Altman analysis revealed that the width of the 95% limits of agreement was larger between the Tonopen XL and the other tonometers ranged from 14.94 to 16.47 mmHg. Among the other tonometers, however, the widths of 95% limits of agreement ranged from 7.91 to 9.24 mmHg. CONCLUSION: There was good inter-device agreement among GAT, rebound tonometers, and NCT. Tonopen XL shows the worst agreement with the other tonometers; therefore, we should pay attention to its' respective IOP. CLINICAL TRIAL REGISTRATION: Japan Clinical Trials Register; number: UMIN000011544.

Rebound Tonometers versus Other Tonometers: Agreement among Readings and the Effects of Axial Length, Ocular Pulse Amplitude, and Central Corneal Thickness on Readings

OBJECTIVE: The aim of this study was to use intraocular pressure (IOP) measurements obtained via rebound tonometry (RBT, the I-care instrument), Goldmann applanation tonometry (GAT), non-contact tonometry (NCT), dynamic contour tonometry (DCT, PASCAL), and the TonoPen to investigate the consistency of readings among methods and the influence of ocular pulse amplitude (OPA), axial length (AL), and central corneal thickness (CCT) on RBT data. METHODS: We prospectively studied 123 eyes. IOP was measured via RBT, GAT, NCT, DCT, and the TonoPen. In addition, OPA was measured via DCT, AL, and CCT. Correlations among measurements using the various methods were evaluated, as were the effects of OPA, AL, and CCT on RBT data. RESULTS: RBT data were significantly correlated with data obtained via GAT, NCT, DCT, and the TonoPen; the highest correlation was with GAT. OPA was significantly correlated with IOP measured via GAT but not with IOP measured via RBT. Both AL and CCT were significantly correlated with IOP data obtained via RBT and GAT. CONCLUSION: Significant correlations were evident among IOP measurements obtained via RBT and other tonometry methods. However, the influence of AL and CCT on IOP measurements obtained via RBT requires careful consideration and interpretation. Although the IOP values obtained by GAT were correlated with OPA values obtained by DCT, this was not true of IOP data obtained by RBT. This might be associated with characteristic of RBT which has the relatively short corneal contact time.

Comparison of intraocular pressure as measured by three different non-contact tonometers and goldmann applanation tonometer for non-glaucomatous subjects.

BACKGROUND: To compare the measurement of intraocular pressure (IOP) among the three different non-contact tonometers (NCT) and the Goldmann applanation tonometer (GAT) for non-glaucomatous subjects. METHODS: In 52 eyes of 52 non-glaucomatous subjects, IOP was measured sequentially with the Canon TX-20P, the Nidek NT-530P, the Topcon CT-1P, and the GAT at the same time. We evaluated the IOP-measurement agreement among the tonometers as well as the factors affecting the measurements. RESULTS: A significant positive correlation was shown between the IOP values obtained with GAT and each NCT. The Canon TX-20P showed statistically the most significant agreement with the GAT (ICC 0.906, 95% CI 0.837-0.946). In an analysis of the Bland-Altman plots, the Canon TX-20P also showed the largest mean bias (1.38 mmHg) but the narrowest limits of agreement (LoA) (95% LoA; ± 3.43 mmHg). The Topcon CT-1P showed the smallest mean bias (0.48 mmHg) but the widest LoA (95% LoA; ± 4.16 mmHg). The Topcon CT-1P and Nidek NT-530P both showed a significantly positive correlation between increasing central corneal thickness (CCT) and increasing IOP. CONCLUSION: There was a statistically significant correlation between each of the three different NCT and the GAT measurements. IOP measured with the Canon TX-20P and Topcon CT-1P tended to be higher, and with the Nidek NT-530P lower, than with the GAT. Practitioners need to know the properties of their own NCTs and their respective measurement tendencies.

Comparison of current tonometry techniques in measurement of intraocular pressure.

PURPOSE: To compare four tonometry techniques: Goldmann applanation tonometer (GAT), Dynamic contour tonometer (DCT), Non-contact tonometer (NCT), and Ocular Response Analyzer (ORA) in the measurement of intraocular pressure (IOP) and the impact of some corneal biomechanical factors on their performance. METHODS: In this cross-sectional study, volunteers with normal ophthalmic examination and no history of eye surgery (except for uncomplicated cataract surgery) or trauma were selected. Twenty-five subjects were male, and 21 were female. The mean age was 48 ± 19.2 years. Anterior segment parameters were measured with Scheimpflug imaging. IOP was measured with GAT, DCT, NCT, and ORA in random order. A 95% limit of agreement of IOPs was analyzed. The impact of different parameters on the measured IOP with each device was evaluated by regression analysis. RESULTS: The average IOP measured with GAT, DCT, NCT, and ORA was 16.4 ± 3.5, 18.1 ± 3.4, 16.2 ± 3.9, and 17.3 ± 3.4 mmHg, respectively. The difference of IOP measured with NCT and GAT was not significant (P = 0.382). Intraocular pressure was significantly different between GAT with DCT and IOPCC (P < 0.001 and P = 0.022, respectively). The 95% limit of agreement of DCT, NCT, and IOPCC with GAT was -5.7 to 2.5, -4.1 to 4.7, and -5.3-3.7 mmHg, respectively. Simple regression model corneal resistance factor (CRF) and central corneal thickness (CCT) and multivariate model CRF had a significant relationship with IOP measured with the four devices. CONCLUSION: Although the mean difference of measured IOP by NCT, DCT, and ORA with GAT was less than 2 mmHg, the limit of agreement was relatively large. CCT and CRF were important influencing factors in the four types of tonometers.

Agreement of intraocular pressure measured by noncontact tonometer and Goldmann applanation tonometer : a Meta-analysis / 中华实验眼科杂志

Background Noncontact tonometer (NCT) is a common application in clinical ophthalmology,while its measured value is influenced by corneal parameter.In recent years,there existed some clinical trials discussing the agreement between NCT and gold standard Goldmann applanation tonometer (GAT),but there was still lack of evidence.Objective This study was to evaluate the agreement between NCT and GAT by applying evidence based medicine (EBM) method.Metbods A systematic literature retrieval was conducted from the MEDLINE,EMbase,CBM disc and CNKI database with the limitation of publishing time until June 2016.The literatures were screened according to the inclusion and exclusion criteria.The sample size,average age,sample characteristics and follow-up time were extracted.The value of intraocular pressure measured by NCT and GAT were analyzed.The overall effect size was analyzed using Review Manager 5.3 (from The Cochrane Collaboration) as weighted mean difference (WMD).There existed heterology in this study.Radom effect mode was used to evaluate and compare the difference between NCT and GAT value.Results Twenty four articles were retrieved.Six comparison studies incorporated with 478 eyes were included for Meta analysis.After random effects model was performed for correction.Intraocular pressure measured by NCT was 0.02 mmHg larger than that by GAT (1 mmHg =0.133 kPa).There was no significant difference in the measurement value of IOP between the two instruments (WMD =0.02,95％ CI:-0.59 to 0.63,P =0.95).Funnel chart method showed that literature publication bias existed in this study.Conclusions Normal persons' IOP obtained from NCT and GAT showed a good reproducibility.More comparison studies are needed to support this result.

Intraocular pressure readings obtained through soft contact lenses using four types of tonometer.

PURPOSE: To compare the reliability and accuracy of intraocular pressure (IOP) measured while wearing soft contact lenses (SCLs) using a non-contact tonometer (NCT), Goldmann applanation tonometer (GAT), iCare rebound tonometer (RBT) and the Tono-Pen XL. METHODS: Twenty-six healthy subjects were examined. The IOP was measured using NCT, GAT, RBT, and the Tono-Pen XL, while the subjects wore SCLs -5.00 D, -0.50 D and +5.00 D. Bland-Altman plots and a regression analysis were used to compare the IOPs obtained with those instruments and the IOPs of the naked eyes measured using GAT (the standard IOPs in this study). RESULTS: The IOPs obtained by the Tono-Pen XL while the subjects were wearing -5.00 D, -0.50 D, and +5.00 D SCLs were significantly higher than those of the naked eyes obtained using GAT. RBT showed that the IOPs were similar to the GAT standard IOPs under all conditions. The IOPs measured with NCT and GAT while the subjects were wearing -5.00 D and -0.50 D SCLs were similar to the GAT standard IOPs. The IOPs obtained with RBT and NCT while the subjects were wearing -5.00 D and -0.50 D SCLs exhibited a good correlation with the standard IOPs. CONCLUSION: The NCT and RBT are best when measuring IOP through hydrogel SCLs.

Clinical comparison of Pulsair non-contact tonometer and Goldmann applanation tonometer in Indian population.

INTRODUCTION: Goldmann applanation tonometer (GAT) is the gold standard for Intraocular Pressure (IOP) measurement but has disadvantage of being contact device and problems with portability. The aim of the study was to compare the Keeler's Pulsair noncontact tonometer (NCT) with GAT in Indian Population. MATERIALS AND METHODS: Eighty-one subjects were screened from a Glaucoma clinic of a tertiary care centre in North India. The IOP was measured by Pulsair NCT and GAT after explaining the procedure. Central corneal thickness (CCT) was measured to avoid its bias on IOP readings. The data were analyzed using SPSS software. RESULTS: The mean age of subjects was 49.9±8.8 (mean±SD) years. The mean IOP as taken by Pulsair NCT was 15.79±4.07mmHg and that for GAT was 17.02±4.23mmHg (p=0.062). The mean CCT was 0.536±0.019mm. A positive Pearson's correlation coefficient of 0.909 (p=0.0001) was found between the two instruments. Bland and Altmann analysis showed a fair agreement between the two tonometers at lower IOP range. CONCLUSION: Pulsair NCT can be used as a screening tool for community practices but is not reliable in the subjects with higher IOP range.

Analysis of Postoperative Intraocular Pressure Underestimation Measured with Non Contact Tonometry after Corneal Refractive Surgery

PURPOSE: To analyze the postoperative intraocular pressure (IOP) underestimation measured with non-contact tonometry after corneal refractive surgery. METHODS: The postoperative IOP decrease measured with non-contact tonometry (NCT), regarded as IOP underestimation, was calculated in 253 LASIK patients and 281 LASEK patients. Multiple regression analysis was performed to determine the preoperative factors which affect postoperative IOP underestimation. The right eye results were reported in this paper. RESULTS: The postoperative IOP decrease was affected by age (r = -0.0420, p = 0.03), corneal ablation depth (r = 0.0466, p < 0.01), and operation method (LASIK or LASEK) (r = 0.6006, p < 0.01). For every 100 microm decrease of corneal thickness by LASIK, the IOP decreased 6.29 +/- 2.40 mm Hg in patients under 26 years of age and 6.12 +/- 2.53 mm Hg in patients above 26 years of age (p = 0.05). For every 100 microm decrease of corneal thickness by LASEK, the IOP decreased 5.77 +/- 2.37 mm Hg in patients under 26 years of age and 5.44 +/- 2.62 mm Hg in patients above 26 years of age (p = 0.05). CONCLUSIONS: The postoperative IOP underestimation measured with NCT was more prominent in younger-aged patients after LASIK than LASEK with deeper ablation depth.

Comparison of Rebound Tonometer, Non-Contact Tonometer, Goldmann Applanation Tonometer and the Relationship to Central Corneal Thickness

PURPOSE: To compare the level of accuracy of intraocular pressure (IOP) measurements of a rebound tonometer (RT) Icare(R), and non-contact tonometer (NCT), using Goldmann Applanation tonometer (GAT) as a reference to evaluate the influence of central corneal thickness (CCT) on IOP readings in the Korean population. METHODS: In a prospective study of 273 eyes, IOP was measured with RT, GAT, and NCT and compared to CCT measurements. Patients were assigned to one of 3 groups based on IOP measurements of GAT and 1 of 2 groups based on CCT. The comparison of the IOP values of RT, GAT, and NCT was performed between the IOP and CCT groups, and the differences among tonometers were evaluated. RESULTS: The RT showed statistically significant correlation with the GAT compared to the NCT. The CCT was related to RT measurements. The RT values compared to the GAT was underestimated in thin corneas and overestimated in thick corneas. CONCLUSIONS: There was a significant correlation between the RT and the GAT measurements compared with the NCT. However, RT is influenced by CCT and correlates less with GAT in low IOP ranges, suggesting that corneal thickness should be taken into consideration during such measurements.