Comparison of intraocular pressure measurements with the tono-pen, goldmann applanation tonometer, and noncontact tonometer in nonglaucomatous pseudophakic children.

BACKGROUND: To evaluate the agreement between the Goldman applanation tonometer (GAT), Tono-Pen, and noncontact tonometer (NCT) in the measurement of intraocular pressure (IOP) in pseudophakic children. METHODS: The medical records of nonglaucomatous pseudophakic children between 2009 and 2019 were retrospectively analyzed. A total of 46 eyes of 23 patients operated for bilateral pediatric cataract were included in the study. The patients' mean age was 13.4 ± 4.1 years. Central corneal thickness (CCT) and IOP values measured with the GAT, Tono-Pen, and NCT were recorded. Agreement between the tonometers was evaluated by intraclass correlation coefficients (ICC) and the Bland-Altman method. RESULTS: The mean IOP of the 46 eyes included in the study was measured as 13.7 ± 2.3 mm Hg with the GAT, 16.0 ± 2.3 mm Hg with NCT, and 16.5 ± 2.3 mm Hg with the Tono-Pen (p < 0.001). There is no statistical difference between NCT and Tono-Pen measurements, while GAT measurements were significantly lower than those of the NCT and Tono-pen. ICC values showed fair agreement between NCT and Tono-Pen (ICC = 0.720), whereas there was poor agreement between GAT and NCT (ICC = 0.501) and Tono-pen (ICC = 0.314). CONCLUSIONS: With all devices included in the study, thicker corneas were associated with higher IOP measurements. Although there was moderate agreement between the NCT and Tono-Pen, there was a statistically significant difference in the IOP values provided by the three devices. Our results suggest these devices should not be used interchangeably.

Predictive models for IOPs measured with NCT, GAT, and ORA among patients undergoing SMILE.

Purpose: To develop predictive models for the intraocular pressure (IOP) of patients undergoing small incision lenticule extraction (SMILE) procedures, measured with a noncontact tonometer (NCT), Goldmann applanation tonometry (GAT), and an ocular response analyzer (ORA). Methods: In this prospective study, a total of 104 eyes (-6.23 ± 2.06 diopters) of 52 patients (24.38 ± 4.76 years) undergoing SMILE procedures were included. The intraocular pressure was measured (IOPNCT with NCT, IOPGAT with GAT, and IOPcc and IOPg with ORA) before surgery and at postoperative 6 months. Information on age, preoperative and attempted spherical equivalent (SE), ablation depth, preoperative values and postoperative changes in central corneal thickness (CCT), K1, K2, Km, corneal hysteresis (CH) and corneal resistance factor (CRF) values was collected in order to predict IOPs. Results: All surgeries were uneventful. At postoperative 6 months, the efficacy and safety index were 1.04 ± 0.15 and 1.08 ± 0.18, respectively. Significant decreases were detected in postoperative IOPNCT, IOPGAT, IOPcc, and IOPg compared to preoperative values (all p < 0.001). No relationship was found between any IOP and ablation depth, attempted SE, and preoperative SE, as well as CCTdifference (all p > 0.05). Predictive models for IOPs were constructed to predict preoperative values, and R 2 values were 67.5% (IOPNCT), 64.5% (IOPGAT), 78.7% (IOPcc), and 82.0% (IOPg). The prediction band of IOPNCT and IOPGAT was 7.4-15.1 mmHg and 8-16 mmHg, respectively. Conclusion: Predictive models for IOP measurements after SMILE procedures can be helpful in clinical practice.

Intrasession and Intersession Variabilities of Intraocular Pressure Measured by Noncontact Tonometer in Normal Volunteers.

PURPOSE: Intraocular pressure (IOP) measured using a noncontact tonometer is evaluated by performing multiple measurements because IOP is affected by the ocular pulse. We investigated the relationship between value fluctuations in multiple measurements during noncontact tonometer measurements and cardiac rate. MATERIALS AND METHODS: Forty-two healthy subjects were included and IOP was measured using a noncontact tonometer. The measurement was performed three times each for the right eye and the left eye, for a total of six times. Blood pressure and cardiac rate were measured at the same time as the IOP measurement. Using repeated-measures analysis of variance, we examined whether the measured IOP and cardiac rate fluctuate throughout the day over the course of 4 days. RESULTS: There was a fluctuation in the IOP in a sequence only on day 1 of the four measurement days (P < 0.001). The IOP on day 1 tended to be high for the first and second measurements (P = 0.0111-0.0015). Systolic blood pressure and diastolic blood pressure did not fluctuate over the 4 days (P = 0.6247 and 0.7132), but cardiac rate was high only on day 1 (P = 0.0276). CONCLUSION: The IOP on day 1 tended to be high in the first and second measurements. The IOP measured on days 2-4 did not fluctuate during the sequence of measurements. The cardiac rate measured at the same time as the IOP was high only on the first day.

Evaluation of Changes in Intraocular Pressure with a Noncontact Tonometer in Healthy Volunteers.

PURPOSE: We investigated whether or not intrasession or intersession fluctuations in intraocular pressure occur in healthy people using a noncontact tonometer. MATERIALS AND METHODS: A noncontact tonometer was used to measure intraocular pressure in the bilateral eyes of healthy subjects for 5 consecutive days. Paired t-tests and one- and two-way repeated-measures analyses of variance were performed for the acquired data. A p-value <0.05 was considered to indicate statistical significance. RESULTS: Eighty eyes of 40 healthy subjects were enrolled in the study. On day 1, intraocular pressure was significantly higher in the right eye than in the left eye (P = 0.014). The one-way repeated-measures analysis of variance revealed that intraocular pressure in the left eye was significantly lower on day 1 than on days 2 to 5 (P = 0.000-0.018); however, there were no significant differences among intraocular pressures measured on days 1 to 5 in the right eye. The two-way repeated-measures analysis of variance revealed no significant difference in intraocular pressure between the right and left eyes (P = 0.913). CONCLUSION: Although measurements using the noncontact tonometer were relatively stable, intraocular pressure was high on day 1.

Comparative Assessment of The Goldmann Applanation and Noncontact Tonometers in Intraocular Pressure Measurements in a Sample of Glaucoma Patients in the Cape Coast Metropolis, Ghana.

OBJECTIVES: The objective of the study was to explore the usage of the Goldmann applanation tonometry and noncontact tonometry interchangeably in the measurement of intraocular pressure (IOP) in glaucoma patients. MATERIALS AND METHODS: The study involved 441 clinically diagnosed glaucoma patients receiving care at a referral facility. IOP measurements were obtained using both the Noncontact tonometer and Goldmann applanation tonometer The repeatability of the measures was analyzed by comparing the repeated measures of the devices using paired t-test and calculating the correlation coefficient. A Bland-Altman analysis was used to determine the limits of agreement between the two procedures. RESULTS: There were 271 (61.5%) males and 170 (38.5%) females and their age ranged from 18 to 73 years (mean age = 49.37; standard deviation ± 14.81 years). The findings of the study showed significantly lower readings (P < 0.001) of the GAT (right eye = 17.40 ± 7.48 mmHg; left eye = 16.80 ± 7.49 mmHg) compared to the NCT (right eye = 20.15 ± 8.30 mmHg; left eye = 19.74 ± 8.31 mmHg). There was a strong positive correlation between the GAT and NCT findings in the right eye (r = 0.871, n = 441, P < 0.001) and in the left eye (r = 0.887, n = 441, P < 0.001). There was a wide limit of agreement between NCT and GAT measurements. CONCLUSION: There was statistically significant higher measures obtained with NCT than the GAT but did not exceed the allowable inter-device difference. There was a strong positive correlation between GAT and NCT measurements. However, it is strongly recommended that these devices are not used interchangeably in the monitoring of IOP in glaucoma due to the wide range of limits of agreement.

Comparative evaluation of applanation and indentation tonometers in a community ophthalmology setting in Southern India.

PURPOSE: Measurement of intraocular pressure (IOP) is one of the basic investigations in a general ophthalmic workup. In this study, we attempt to determine the agreement in the measurement of IOP obtained by Perkin's applanation tonometer, noncontact tonometer and Schiotz indentation tonometer in patients attending general ophthalmology OPD in a tertiary care centre in South India and its use in a community ophthalmology setting. METHODS: A cross-sectional analytical study in which IOP was measured in patients using the three tonometers. Central corneal thickness (CCT) was measured using Ultrasonic pachymetry. Bland Altman analysis was done to evaluate the agreement between instruments. RESULTS: 800 eyes of 400 patients were included in the study. By Bland Altman method, Schiotz indentation tonometer was found to have better correlation to IOP obtained by Perkin's applanation tonometer. Schiotz indentation tonometer was found to be most accurate when CCT was in the range of 501-550 µm and noncontact tonometer was found to be least accurate when CCT was greater than 600 microns. On comparing correlation at different age groups, both the methods had better correlation at <40 years age group. CONCLUSION: Both the tonometers showed a significant correlation with the gold standard technique (Perkin's applanation tonometer) over a range of IOP and CCT with the Schiotz tonometer better than the NCT. This study proves that Schiotz tonometer can be recommended as a reliable screening tool in community outreach ophthalmology services. The twin advantages of portability and availability make the Schiotz tonometer a popular choice among ophthalmology trainees and optometrists in a developing country like India.

Intraocular pressure measurement by three different tonometers in primary congenital glaucoma.

PURPOSE: To determine the agreement between intraocular pressure (IOP) measurements using an automated non-contact tonometer (NCT), Goldmann applanation tonometer (GAT), and the ocular response analyzer (ORA) in subjects with primary congenital glaucoma (PCG). METHODS: Twenty-nine eyes of 17 PCG patients underwent IOP measurements using NCT, GAT and ORA. Variables obtained by the ORA were corneal-compensated IOP (IOPcc), Goldmann-correlated IOP (IOPg), corneal hysteresis (CH), and corneal resistance factor (CRF). A difference more than 1.5 mmHg for IOP was considered as clinically relevant. RESULTS: Mean age of the patients was 12 years. Mean IOP (±standard deviation, SD) was 15.3 ± 2.8 mmHg (GAT), 15.5 ± 6.0 (NCT), 19.2 ± 7.0 (IOPg), and 21.1 ± 7.9 (IOPcc); (P = 0.001). Except for NCT vs. GAT (P = 1.0), the average IOP difference between each pair of measurements was clinically relevant. The 95% limits of agreements were - 10.2 to 10.3 mmHg (NCT vs. GAT), -7.8 to 15.3 (IOPg vs. GAT), and - 8.1 to 19.0 (IOPcc vs. GAT). The differences in IOP measurements increased significantly with higher average IOP values (r = 0.715, P = 0.001, for NCT vs. GAT; r = 0.802, P < 0.001, for IOPg vs. GAT; and r = 0.806, P < 0.001, for IOPcc vs. GAT). CH showed a significant association with differences in IOP measurements only for IOPcc vs. GAT (r = 0.830, P < 0.001). CONCLUSION: Mean IOP obtained by NCT was not significantly different from that of GAT, but ORA measured IOPs were significantly higher than both other devices.

Corneal biomechanical properties: precision and influence on tonometry.

PURPOSE: To assess the precision and reproducibility of the corneal biomechanical parameters, and their relationships with the intraocular pressure (IOP) measured with the Goldmann tonometer and a noncontact tonometer. METHODS: Readings for biomechanical properties and for IOP measured with the Goldmann and noncontact tonometers, were taken on one randomly selected eye of 106 normal subjects, on each one of two measurement sessions. Measurements with the ocular response analyzer (ORA) and the noncontact tonometer were randomized, followed by the measurement of central corneal thickness and with the Goldmann tonometer. RESULTS: Repeatability coefficients for CCT, corneal hysteresis (CH) and corneal resistance factor (CRF) in Session 1 were ± 0.01 µm, ± 3.05 mmHg and ± 2.62 mmHg, respectively. The mean CCT, CH, CRF, Goldmann and noncontact tonometry did not vary significantly between sessions. Reproducibility coefficients for CCT, CH and CRF were ± 0.02 µm, ± 2.19 mmHg and ± 1.97 mmHg, respectively. Univariate regression analysis showed that CCT, CH and CRF significantly (P<0.0001) correlated with the IOP measured with the Goldmann and noncontact tonometers (and with the differences between tonometers) in Session 1. There were no significant correlations with the differences between tonometers in Session 2. Multivariate analysis revealed a minimal effect of CCT on Goldmann measurements but a significant effect on those of the noncontact tonometer. CONCLUSIONS: Measurement of the biomechanical properties of the cornea, using the ORA, are repeatable and reproducible, affect Goldmann tonometry less than noncontact tonometry, and have a minimal influence on the difference in measured intraocular pressure between tonometers.

Intraocular Pressure Measurement with the Noncontact Tonometer and Rebound Tonometer through Plano Soft Contact Lenses

PURPOSE: To investigate the accuracy of intraocular pressure (IOP) measurement through a plano soft contact lens (SCL) in situ by a noncontact tonometer (NCT) and a rebound tonometer (RBT). METHODS: The IOP of 66 eyes of 33 subjects with no ocular pathology was measured by NCT (tonometer CT-80, TOPCON, Japan) and RBT (iCare rebound tonometry(TM), Tiolat Oy, Finland). IOP measurement was repeated through plano SCL (ACUVUE OASYS(R), Johnson & Johnson Vision Care Inc., USA) in situ. Statistical analysis was performed using the paired t-test. RESULTS: Mean IOP measured by NCT was 13.10 +/- 2.52 mmHg without SCL and 12.95 +/- 2.56 mmHg with SCL. Mean IOP measured by RBT was 14.13 +/- 2.94 mmHg without SCL and 13.84 +/- 2.75 mmHg with SCL. No significant statistical differences were found between IOP measured with and without SCL (p=0.47, p=0.11 respectively). CONCLUSIONS: Reliable measurement of IOP by NCT and RBT can be achieved through plano SCL.

Two-position measurement of intraocular pressure by PT100 noncontact tonometry in comparison with Goldmann tonometry.

BACKGROUND: The purpose of this study was to evaluate the precision of intraocular pressure measurements obtained by PT100 noncontact tonometry in a handheld and slit lamp-mounted position in comparison with that of Goldmann applanation tonometry in healthy young adults. METHODS: Sixty eyes from 60 subjects (30 men and 30 women) aged 22 ± 1 (range 20-24) years participated in this study. Triplicate intraocular pressure measurement of a randomly selected eye was obtained by a noncontact tonometer in a handheld and slit lamp-mounted position in a randomized order, with the Goldmann applanation tonometer always performed last. A second measurement session was carried out after one week to assess repeatability. RESULTS: The mean ± standard deviation of intraocular pressure readings in the first and second session, respectively, with the three techniques were: handheld position, 14.52 ± 3.28 mmHg and 15.26 ± 2.11 mmHg; slit lamp-mounted position, 14.01 ± 2.80 mmHg and 15.16 ± 2.34 mmHg; and Goldmann applanation tonometer, 14.86 ± 3.26 mmHg and 15.16 ± 2.42 mmHg. There were no significant differences (P > 0.05) between the techniques in the intraocular pressure measurements returned (Goldmann applanation tonometer vs handheld and Goldmann applanation tonometer vs slit lamp-mounted). The Goldmann applanation tonometer measured intraocular pressure 0.34 mmHg higher than handheld and 0.85 mmHg higher than slit lamp-mounted in session 1, and in session 2 Goldmann applanation tonometer intraocular pressure measurement was the same as with the slit lamp-mounted method but lower than with the handheld method by 0.11 mmHg. In PT100 handheld vs slit lamp-mounted comparisons, there were no significant differences (P > 0.05) between intraocular pressure measurements returned by both techniques in sessions 1 and 2. Intrasession and intersession repeatability coefficients for Goldmann applanation tonometer intraocular pressure and slit lamp-mounted intraocular pressure were similar, and better in comparison with those for handheld intraocular pressure. CONCLUSION: The Goldmann applanation tonometer and PT100 noncontact tonometer in both positions studied here are reliable, consistent techniques for measurement of intraocular pressure, and can be used interchangeably for obtaining intraocular pressure values in young normal subjects. Repositioning of the PT100 tonometer from hand-held to slit lamp-mounted improved its precision and reduced variation with respect to the Goldmann applanation tonometer.

Performance of the PT100 noncontact tonometer in healthy eyes.

BACKGROUND: The purpose of this study was to assess the repeatability and reproducibility of the PT100 noncontact tonometer and to compare its consistency with the Goldmann applanation tonometer (GAT) in measuring intraocular pressure (IOP). METHODS: Triplicate IOP measurements were obtained on two separate occasions using the PT100 and GAT from randomly selected eyes in 66 healthy volunteers aged 22 ± 1 years. The repeatability and reproducibility of each techniques was assessed. Agreement between the techniques was statistically quantified using intrasession repeatability for each technique as the basis for comparison. RESULTS: Both techniques returned equal IOP values in the first measurement session (15 ± 3 mmHg). The second session showed a mean difference in average IOP (1 ± 0.71). The 95% limits of agreement between the techniques were -5.2 to 5.5 mmHg and -4.0 to 4.7 mmHg (sessions 1 and 2, respectively). These mean differences were not statistically significant (P > 0.05, paired t-test), with the PT100 underestimating IOP measurement by 1.00 mmHg. The mean intrasession IOP for GAT sessions 1 and 2 was 0 ± 0.90 mmHg and 0.04 ± 1.06 mmHg, respectively, and the corresponding mean IOP measurement difference for the PT100 was -0.06 ± 0.96 and -0.39 ± 0.94 mmHg (sessions 1 and 2, respectively; P > 0.05, paired t-test). Repeatability coefficients for the GAT IOP measurements were 1.8 mmHg and 2.1 mmHg for sessions 1 and 2, while the PT100 repeatability coefficient was 1.9 mmHg and 1.8 mmHg for sessions 1 and 2, respectively. The intrasession repeatability coefficient of both techniques for test-retest differences were within ±5 mmHg. CONCLUSION: The PT100 noncontact tonometer produced greater repeatability than the GAT in assessment of IOP, whereas GAT resulted in more reproducible results. Both techniques showed a close level of agreement on comparison, with the PT100 underestimating IOP measurement by 1.0 mmHg only, although this was not clinically or statistically significant. Of importance is that the IOP measurements using these techniques could be interchangeable in the IOP range studied here.

Difference between Goldmann Applanation and Topcon Noncontact Tonometer Measurements after Excimer Laser Photorefractive Keratectomy

The authors' clinical experience has suggested that the noncontact tonometer (NCT) has a tendency to record a lower intraocular pressure(IOP) than the Goldmann applanation tonometer(GAT) after excimer laser photo refractive keratectomy(PRK). This study was done to verify this tendency. We performed PRK on 177 eyes of 122 patients using a VISX 20/20 excimer laser, and topical fluorometholone was used after PRK. The eyes were divided into three groups according to their ablation depths, and the IOP was measured with the GAT and the Topcon NCT before surgery and 1, 3, 6, 9, and 12 months postoperatively. The mean postoperative IOP measured with the GAT or the NCT decreased as compared with the mean preoperative IOP(GAT: 1.67 ~ 2.90 mmHg, NCT:5.27 ~ 6.54 mmHg). The mean NCT reading was 1.12 mmHg higher than the mean GAT reading preoperatively, but was 2.48 ~ 2.88 mmHg lower than the mean GAT reading postoperatively. Difference between GAT and NCT measurements postoperatively was more prominent in the group of deeper ablation. These results suggest that we should be cautious of evaluating the IOP measured with the GAT or the NCT after PRK.