Intraocular pressure measurements with the Proview self-tonometer in comparison of Goldmann applanation tonometry in healthy and glaucomatous eyes

BACKGROUND: The aim of this study was to compare the results of intraocular pressure (IOP) measurements obtained using the pressure phosphene tonometer Proview with those from Goldmann applanation tonometer (GAT) in normal and glaucomatous eyes. PATIENTS AND METHODS: The IOP in 150 eyes of 62 healthy volunteers and 88 patients with glaucoma or ocular hypertension was measured prospectively in a sitting position. After being trained to use the Proview device, Goldmann applanation tonometry was performed first. Then the patient took a reading with the Proview self-tonometer. RESULTS: For all investigated eyes the measurements with the Proview were on average 5.5 mmHg higher than those by GAT. Only 34 % of the readings from the two devices were within a difference range of +/- 3 mmHg. On comparing the group of glaucomatous patients with slight visual field defects with the group of healthy subjects and patients with ocular hypertension without visual field defects we determined almost the same mean difference between the Proview and GAT (mean difference in the group with visual field defects = 4.7 +/- 4.1 mmHg; without defects = 4.8 +/- 2.9 mmHg). CONCLUSIONS: The tonometer Proview did not show a close agreement to GAT. Therefore, the PPT does not offer an alternative method for measuring IOP. We do not recommend the Proview for self-tonometry at home or for clinical management of patients with glaucoma. Slight visual field defects seem to have no influence on intraocular pressure measurement with the self-tonometer.     

Reproducibility of self-measured intraocular pressure with the phosphene tonometer in patients with ocular hypertension and early to advanced glaucoma

PURPOSE: To evaluate the reproducibility of self-measured intraocular pressure with the Proview tonometer in ocular hypertensives and early to advanced glaucoma patients. PATIENTS AND METHODS: Thirty-three patients with glaucoma and three with ocular hypertension (72 eyes) were prospectively enrolled. History of cornea surgery was the only exclusion criterion. A trainer took a set of three readings first. Subsequently, the patient (after successful training) took one set of three readings and a physician took two sets of three Goldmann readings. One hour later this was repeated. RESULTS: 72% of patients could see the phosphene in both eyes, 8% could see it in one eye, and 19% could not see it in either eye. Patients who could not see the Phosphene had an average mean deviation of -10.9 compared with -3.4 for those who could see it (P = 0.01). Eyes that could not see the phosphene were excluded from further analysis. The average absolute difference between two Proview measurements one hour apart was 1.76 +/- 1.76 mm Hg (r = 0.71). The measurement error (difference between Goldmann and Proview readings) tended to remain constant between sets of measurements taken one hour apart (average error was 2.4 +/- 2.1 mm Hg, r = 0.85). No adverse event was recorded. CONCLUSIONS: Repeated self-tonometry measurements showed very good reproducibility. The systematic, reproducible error between Proview and Goldmann readings may be clinically acceptable and suggests that a baseline "calibration" should be obtained for each patient before the Proview values are used clinically. Self-administered tonometry can play a role in the clinical care of ocular hypertensive and glaucoma patients with the possible exception of very advanced cases.     

Is the tono-pen accurate for measuring intraocular pressure in young children with congenital glaucoma?

PURPOSE: We sought to compare intraocular pressure (IOP) measurements by Perkins tonometer and Tono-Pen in young children with primary congenital glaucoma (PCG). METHODS: This was a retrospective comparative case series. We reviewed the clinical records of all children with primary congenital glaucoma who underwent examinations under general anesthesia at Soroka University Medical Center between January 1999 and July 2002. Our main outcome measures were IOP with Perkins hand-held tonometer and Tono-Pen tonometer. RESULTS: A total of 28 eyes of 16 children were examined under general anesthesia. The mean IOP was 18 +/- 6 mm Hg with the Perkins tonometer and 22 +/- 8 mm Hg with the Tono-Pen. In 18 eyes, IOP was less than 21 mm Hg with the Perkins tonometer; these eyes had already undergone surgical procedures. The other 10 eyes with IOP greater than 21 mm Hg with the Perkins tonometer underwent surgery at the end of the examination under anesthesia. In eyes with IOP greater than 16 mm Hg (Group A, n = 18), a significant difference (P < 0.001) was found between the Perkins and Tono-Pen measurements, even although the values were strongly correlated (r = 0.60). In contrast, in eyes with IOP less than 16 mm Hg (Group B, n = 10) no statistically significant difference (P = 0.28) and good correlation (r = 0.78) were obtained. A difference of 5.8 +/- 3.8 mm Hg and 0.6 +/- 1.7 mm Hg between Perkins and Tono-Pen readings, respectively, was found in Groups A and B. CONCLUSIONS: Tono-Pen readings disagree with Perkins tonometer measurements for measuring IOP in children with PCG who present with IOP greater than 16 mm Hg and tends to overestimate IOP. A further study with a similar population is necessary to confirm these results.     

Pressure phosphene self-tonometry in a patient with Posner-Schlossman syndrome

Studies have shown that pressure phosphene tonometry (PPT) may be applied to glaucoma patients. It has the potential for patients to self-monitor the intraocular pressure (IOP) at home. We describe the successful use of this approach in a patient with Posner-Schlossman syndrome. In the first part of the study, we investigated whether our patient could use PPT accurately and reliably. In the second part of the study, our patient performed daily home self-tonometry, and was educated to seek ophthalmic assessment if his self-measured IOP was >or=21 mmHg. The outcome measurements included IOP and the number of unscheduled attendances for ophthalmic assessment. The use of PPT reduced his number of unscheduled hospital visits from 0.82 to 0.47 visits per month. PPT can be applied with accuracy, reliability and safety in patients with Posner-Schlossman syndrome, with potential benefits in reducing unnecessary ophthalmic attendances by nearly 50%.     

Comparison of ICare tonometer with Goldmann applanation tonometer in glaucoma patients

PURPOSE: To compare the intraocular pressure (IOP) readings taken with the new ICare tonometer and with the Goldmann applanation tonometer (GAT) and to evaluate the influence of central corneal thickness (CCT) on the IOP measurements. PATIENTS AND METHODS: One eye of 178 consecutive patients with primary open-angle glaucoma underwent ultrasonic CCT measurement, followed by IOP evaluation with the GAT and with the ICare tonometer. The deviation of ICare readings from GAT values, corrected according to the Doughty and Zaman formula, was calculated and correlated to CCT by a linear regression model. The agreement between the 2 devices was assessed by use of the Bland-Altman method. RESULTS: The average CCT was 552+/-39 mum. The mean IOP and the mean corrected IOP with GAT were 19.4+/-5.4 mm Hg, and 18.5+/-5.7 mm Hg, respectively. The mean ICare IOP reading was 18.4+/-5.2 mm Hg. The deviations of ICare readings from corrected GAT values were highly correlated with CCT values (r=0.63, P<0.01). Linear regression analysis showed that a CCT change of 10 mum resulted in an ICare reading deviation of 0.7 mm Hg. The Bland-Altman scatter-plot showed a reasonable agreement between the 2 tonometers. CONCLUSIONS: The ICare tonometer can be useful in a routine clinical setting. The IOP readings are quite in accordance with those obtained by GAT. The measurements seemed to be influenced by CCT variations, and thus pachymetry should always be taken into consideration.     

Level of disagreement between Proview phosphene tonometer and Goldmann applanation tonometer intraocular pressure readings

PURPOSE: To evaluate the agreement of intraocular pressure (IOP) readings obtained with the Proview phosphene tonometer and those obtained by Goldmann applanation tonometry as well as the effect of regular use of the Proview on patients' anxiety about their glaucoma. METHODS: One hundred thirty-five consecutive patients with glaucoma, 35 designated as controls, were enrolled in a 10-month randomized prospective clinical trial. The study patients but not the controls used the Proview outside the office. At office visits IOP was measured by an ophthalmologist with the Goldmann applanation tonometer (GAT) as well as by examiners and patients using the Proview. Patients in the treatment group (n = 100) were asked to measure and record their IOP at home as well. Using ANOVA, we examined the relationship between demographic variables and the level of agreement between the Proview readings and those measured by GAT at the final office visit. All participants also were asked to complete a questionnaire regarding their anxiety about their IOP at the baseline and final office visits. The primary outcome measure was the level of agreement of the Proview measurements with those obtained by GAT. Secondary outcome measures included patients' anxiety about their glaucoma. RESULTS: The absolute mean difference between GAT and Proview readings at the final visit was 3.5 +/- 2.9 mm Hg (median, 2.8 mm Hg). The treatment group reported significantly less anxiety about their glaucoma after 4 to 6 weeks of using the Proview (P = .024). CONCLUSIONS: There was considerable discrepancy between Proview and GAT readings. However, regular use of the Proview tonometer significantly reduced patients' anxiety about their glaucoma.     

Reproducibility and clinical evaluation of rebound tonometry

PURPOSE: To establish the reproducibility of a rebound tonometer in humans and the effect of corneal thickness on measurements, comparing it with Goldmann applanation tonometer. METHODS: In a first study designed to examine the reliability of the RBT, three experienced ophthalmologists undertook three consecutive intraocular pressure (IOP) measurements in 12 eyes of 12 normal subjects. A cross-sectional study was then performed to compare measurements obtained using the two tonometers in 147 eyes of 85 patients with ocular hypertension or glaucoma. RESULTS: Intraobserver coefficients of correlation obtained in the reproducibility study were 0.82, 0.73, and 0.87. Interobserver correlation was 0.82. There was a good correlation between IOP readings obtained by the RBT and the GAT (r = 0.865, P < 0.0001). RBT readings were consistently higher than GAT measurements (median difference, 1.8 +/- 2.8 mm Hg). A Bland-Altman plot indicated the 95% limits of agreement between the two methods were -3.7 to 7.3 mm Hg (slope = -0.022, P = 0.618). Using RBT, the point that best discriminated between patients with an IOP < or = 21 mm Hg and those with >21 mm Hg, as determined by the GAT was >23 mm Hg (sensitivity, 70.5%; specificity, 95.1%). In terms of pachymetry, the two tonometers behaved in a similar way, with correlation observed between IOP measurements and central corneal thickness. CONCLUSIONS: Rebound tonometry is a reproducible method of determining IOP in humans. In general, it tends to overestimate IOP compared with Goldmann applanation tonometry. The tonometers used in both methods are similarly affected by pachymetry.     

Ocular response analyzer versus Goldmann applanation tonometry for intraocular pressure measurements

PURPOSE: To establish correlations between intraocular pressure (IOP) measurements obtained with the ocular response analyzer (ORA) and the Goldmann applanation tonometer (GAT). The effects of central corneal thickness on the measures obtained were also examined. METHODS: This was a cross-sectional study. IOP was determined in 48 eyes of 48 patients with glaucoma In all patients, central corneal thickness (CCT) was measured by ultrasound pachymetry. RESULTS: ORA readings were consistently higher than GAT measurements (Goldmann-correlated IOP - IOP GAT mean difference, 7.2 +/- 3.5 mm Hg; corneal-compensated IOP - IOP GAT mean difference, 8.3 +/- 4.0 mm Hg) However, differences were not constant and increased with increasing IOP GAT readings, both with respect to Goldmann-correlated IOP (slope = 0.623, P < 0.0001) and corneal-compensated IOP (slope = 0.538, P < 0.0001). Both pressure measurements provided by the ORA showed significant correlation with CCT (CCT versus Goldmann-correlated IOP: r = 0.460, P = 0.001; CCT versus corneal-compensated IOP: r = 0.442, P = 0.001). No significant effects of corneal curvature or refraction on any of the pressures were observed. CONCLUSIONS: The ORA significantly overestimates IOP compared with the GAT. Differences between both sets of measures increase as the GAT-determined IOP increases. ORA readings seem to be affected by central corneal thickness.     

A comparison of four methods of tonometry: method agreement and interobserver variability

AIM: To compare the inter-method agreement in intraocular pressure (IOP) measurements made with four different tonometric methods. METHODS: IOP was measured with the Goldmann applanation tonometer (GAT), Tono-Pen XL, ocular blood flow tonograph (OBF), and Canon TX-10 non-contact tonometer (NCT) in a randomised order in one eye of each of 105 patients with ocular hypertension or glaucoma. Three measurements were made with each method, and by each of two independent GAT observers. GAT interobserver and tonometer inter-method agreement was assessed by the Bland-Altman method. The outcome measures were 95% limits of agreement for IOP measurements between GAT observers and between tonometric methods, and 95% confidence intervals for intra-session repeated measurements. RESULTS: The mean differences (bias) in IOP measurements were 0.4 mm Hg between GAT observers, and 0.6 mm Hg, 0.1 mm Hg, and 0.7 mm Hg between GAT and Tono-Pen, OBF, and NCT, respectively. The 95% limits of agreement were smallest (bias +/-2.6 mm Hg) between GAT observers, and larger for agreement between the GAT and the Tono-Pen, OBF, and NCT (bias +/-6.7, +/-5.5, and +/-4.8 mm Hg, respectively). The OBF and NCT significantly underestimated GAT measurements at lower IOP and overestimated these at higher IOP. The repeatability coefficients for intra-session repeated measurement for each method were +/-2.2 mm Hg and +/-2.5 mm Hg for the GAT, +/-4.3 mm Hg for the Tono-Pen, +/-3.7 mm Hg for the OBF, and +/-3.2 mm Hg for the NCT. CONCLUSIONS: There was good interobserver agreement with the GAT and moderate agreement between the NCT and GAT. The differences between the GAT and OBF and between the GAT and Tono-Pen probably preclude the OBF and Tono-Pen from routine clinical use as objective methods to measure IOP in normal adult eyes.     

Noninvasive measurement of rodent intraocular pressure with a rebound tonometer

PURPOSE: The present study evaluated the applicability of a rebound tonometer in measuring intraocular pressure (IOP) in rats and mice. METHODS: The accuracy of the TonoLab rebound tonometer was determined in cannulated mouse and rat eyes. IOP was manipulated by changing reservoir height, and tonometer pressure readings were recorded by an independent observer. IOP values were recorded in conscious Wistar rats and in four different strains of mice. The effects of anesthesia on IOP were evaluated in two different strains of mice. RESULTS: The IOP readings generated by the rebound tonometer correlated very well with the actual pressure in the eye. In rats, this linear correlation had a slope of 0.96 +/- 0.05 (mean +/- SEM, n = 4) and a Y-intercept of -2.1 +/- 1.2. In mice, the slope was 0.99 +/- 0.05 (n = 3), and the Y-intercept was 0.8 +/- 1.4. Using this method, the resting IOP of conscious male Wistar rats was observed to be 18.4 +/- 0.1 mm Hg (n = 132). In mice, strain differences in IOP were detected. Baseline IOP values in Balb/c, C57-BL/6, CBA, and 11- to 12-month-old DBA/2J mice were 10.6 +/- 0.6, 13.3 +/- 0.3, 16.4 +/- 0.3, and 19.3 +/- 0.4 mm Hg (n = 12), respectively. In separated studies, anesthesia lowered IOP from 14.3 +/- 0.9 to 9.2 +/- 0.5 mm Hg (n = 8) in C57-BL/6 mice, and from 16.6 +/- 0.4 to 9.4 +/- 0.6 mm Hg (n = 10) in CBA mice. CONCLUSIONS: The rebound tonometer was easy to use and accurately measured IOP in rats and mice. This technique, together with advances in genetic and other biological studies in rodents, will be valuable in the further understanding of the etiology and pathology of glaucoma.     

Clinical evaluation of the intraocular pressure in patients with glaucoma or ocular hypertension by a self-assessable tonometer.

PURPOSE: To investigate the clinical efficacy of a new patient-operated intraocular pressure tool, the Proview eye pressure monitor (PEPM; Bausch & Lomb, Inc., Rochester, NY), for monitoring intraocular pressure (IOP) in patients with glaucoma or ocular hypertension. PATIENTS AND METHODS: One hundred and forty eyes of 70 Taiwanese patients from the Tri-Service General Hospital (Taiwan, Republic of China) who had been diagnosed with ocular hypertension or glaucoma were studied. After being fully trained during an initial clinic visit, patients measured their own IOP with the PEPM at home. The IOPs were measured again using a Haag-StreitBern Goldmann tonometer (GT; Haag-Streit, K?niz, Switzerland) during subsequent outpatient visits. The training time, assessment of the patients' ease of PEPM use, and accuracy of measured PEPM IOPs in relation to GT IOPs were recorded and analyzed. RESULTS: Relative to GT readings, PEPM readings tended to be overestimated at lower pressure (<10 mmHg) and underestimated at higher pressure (>20 mmHg). Between 10 to 20 mmHg, PEPM measurements did not significantly differ from GT measurements. Up to 80% of the PEPM measurements fell within +/- 3 mmHg of the corresponding GT readings. When consideration was limited to GT readings of > or =21 mmHg, PEPM measured IOPs of > or =21 mmHg with a sensitivity of 80% and a specificity of 90%. The mean satisfaction rating of PEPM use was 88.3 +/- 2.0 (maximum, 100). The mean training time for appropriate use of PEPM was 17.9 +/- 4.0 minutes. The older the patients, the longer the training time that was required. CONCLUSION: Our data suggest that after appropriate training: (1) PEPM and GT measurements correspond well between 10 mmHg and 20 mmHg and (2) PEPM could offer patients with glaucoma or ocular hypertension an easy-to-use, substantially reliable means of selfmonitoring IOP.     

The effect of corneal edema on dynamic contour and goldmann tonometry

PURPOSE: To determine the effect of contact lens-induced corneal edema on measurements of intraocular pressure (IOP) using the Pascal dynamic contour tonometer (DCT), compared with the Goldmann tonometer. METHODS: Thirty young healthy subjects (23.0 +/- 3.0 years) were recruited from the student population at the University of New South Wales. Thick hydroxyethyl methacrylate contact lenses were worn monocularly for 2 hours under closed-eye conditions to induce corneal edema via hypoxia. IOP (Goldmann and Pascal DCT), ocular pulse amplitude (OPA), and central corneal thickness (CCT) were measured in both eyes before and after lens wear. Paired t-tests, Pearson correlation, and Bland-Altman plots were used to identify changes in, and relationships between, these parameters resulting from corneal edema. RESULTS: Lens wear resulted in statistically significant changes in CCT (+48.3 +/- 14.4 microm, p < 0.001), Goldmann IOP (+1.5 +/- 2.8 mm Hg, p = 0.007), and Pascal DCT IOP (-0.7 +/- 1.1 mm Hg, p = 0.001) but not OPA (0.0 +/- 0.3 mm Hg, p = 0.721, two-tailed paired t-test). The Pascal DCT provided IOP readings that were 1.3 +/- 2.0 mm Hg higher than the Goldmann IOP readings when hydration was normal, but the Goldmann tonometer provided readings that were 0.8 +/- 2.5 mm Hg higher than the Pascal DCT readings when the cornea was edematous. The variation between the two instruments was weakly correlated to the change in CCT (r = -0.261, p = 0.044). CONCLUSIONS: Contact lens-induced corneal edema caused a small underestimation error in IOP measurements by the Pascal DCT, and an overestimation error in Goldmann tonometry measurements. The OPA measurement provided by the Pascal DCT is insensitive to corneal edema-induced changes in corneal properties.     

Assessment of true intraocular pressure: the gap between theory and practical data

A precise assessment of the intraocular pressure (IOP) is crucial for diagnosis and decision making regarding treatment modalities in patients with glaucoma. Recent epidemiologic studies show that a difference of only 1 mm Hg in the mean IOP may be critical enough to determine the visual field prognosis in patients with glaucoma. However, the Goldmann applanation tonometer, which is current gold standard, is not precise enough to measure the true IOP within an error of 1 mm Hg. There are many clinically proposed correction algorithms to correctly measure IOP. However, corrections using only the central corneal thickness and curvature may not be sufficient in each individual case. In this article, previously reported theoretical equations about the effects of corneal topography, modulus of elasticity, and tear film on Goldmann applanation tonometric IOP readings were reviewed, and their discrepancies with clinical or experimental data were analyzed. Thereafter, new tonometers such as the dynamic contour tonometer, the rebound tonometer, and the ocular response analyzer were compared with the Goldmann applanation tonometer and other popular tonometers.     

Comparison of dynamic contour tonometry and noncontact tonometry in ocular hypertension and glaucoma

PURPOSE: To assess the agreement in the measurement of intraocular pressure obtained by dynamic contour tonometer (DCT) and noncontact tonometer (NCT) in patients with glaucoma and ocular hypertension, to investigate the effect of corneal thickness on pressure readings by both instruments, and to assess the reproducibility of dynamic contour tonometer. METHODS: NCT and DCT measurements were made on 104 eyes of 104 patients with primary open-angle glaucoma (n=75) or ocular hypertension (n=29), and agreement was assessed by means of Bland-Altman plots. The effect of corneal thickness on both tonometers was assessed by linear regression analysis. Interobserver and intraobserver variations for dynamic contour tonometer were assessed in 41 eyes of 41 patients. RESULTS: The mean difference+/-SD (95% limits of agreement) between NCT and DCT was -0.80+/-2.98 (-6.6 to 5.1) mm Hg (P=0.009) and no relation between NCT/DCT differences and average was found. The intraocular pressure readings obtained by noncontact tonometer depended on central corneal thickness (P<0.001, adjusted r(2)=0.301). However, dynamic contour tonometer readings showed no effect of corneal thickness (P=0.388, adjusted r(2)=-0.002). The coefficient of repeatability for DCT was 0.92 (95% CI 0.85-0.96, P=0.001). CONCLUSION: In subjects with primary open-angle glaucoma and ocular hypertension, NCT and DCT readings are not interchangeable. DCT measurements, unlike NCT measurements, did not depend on corneal thickness.     

Central corneal thickness in primary open angle glaucoma, pseudoexfoliative glaucoma, ocular hypertension, and normal population

PURPOSE: This study was designed to determine the relationship between central corneal thickness (CCT) and intraocular pressure (IOP) measured by applanation tonometer in glaucomatous, ocular hypertensive, and normal eyes. METHODS: A total of 125 subjects were included in the study. Twenty-six had primary open angle glaucoma (POAG), 25 had pseudoexfoliative glaucoma (PXG), 24 had ocular hypertension (OHT), and 50 of them were normal. IOP values were measured by Goldmann applanation tonometer whereas CCT values were measured by ultrasonic pachymeter. RESULTS: CCT values in the OHT group (595.75+/-22.52 microm) were greater than the CCT values of the POAG group (539.92+/-21.50 microm), the PXG group (526.28+/-31.73 microm), and the normal group (533.96+/-29.25 microm) (p<0.05). Eight patients who were diagnosed with OHT showed IOP values of 21 mm Hg or lower with corrected IOP values according to CCT. CONCLUSIONS: Increased CCT may lead to falsely high values of IOP measured with Goldmann applanation tonometer. In this study, when IOP values of the OHT group were redefined according to the formulae regarding the CCT, the authors noted that one third of them were normal. Determination of the CCT in OHT cases is crucial since it has great impact on IOP values, measured with applanation tonometer, which is the main parameter in the diagnosis and follow-up of glaucoma.     

Does corneal ocular "pseudo-hypertension" exist?]

BACKGROUND: The relation between Goldmann applanation tonometry and central corneal thickness (CCT) was evaluated in several studies during the last thirty years. Patients with ocular hypertension were found to have a significantly higher CCT compared with normals and glaucomas. PATIENTS: To report on two sisters with elevated CCT and ocular hypertension diagnosed by raised intraocular-pressure (IOP) readings on Goldmann applanation tonometry. RESULTS: In both patients, there were no signs for early functional or morphological glaucomatous changes. Maximum IOP was 30 mm Hg and 26 mm Hg. The corneal pachymetry revealed an increased CCT in both patients (700 and 680 microns, respectively), while corneal morphology was normal. CONCLUSIONS: Ocular hypertension can be misdiagnosed by too high applanation tonometer readings in patients with markedly elevated CCT. Before the onset of treatment thus, corneal pachymetry should be performed in patients with ocular hypertension to exclude ocular "pseudohypertension" and to avoid unneccessary treatment.     

Accuracy of the ICare rebound tonometer in glaucomatous eyes with topical ocular hypotensive medication.

BACKGROUND: The purpose of this study was to assess the accuracy of the ICare tonometer, using the Perkins applanation tonometer (AT) as the reference, in a sample population being treated with travaprost 0.004% for glaucoma. MATERIAL AND METHODS: Twenty-eight consecutive patients with open-angle glaucoma or ocular hypertension who had been receiving travaprost 0.004% to control elevated intraocular pressure (IOP) were included in the study. IOP was measured in the entire sample with ICare and Perkins AT. The difference between the methods was plotted against the mean to compare the tonometers. The hypothesis of zero bias was examined by a paired t-test. The 95% limits of agreement (LoA) were also calculated. RESULTS: As previously found in young healthy subjects, ICare showed a tendency to overestimate Perkins IOP measurements by a mean of 3.57 mmHg. The agreement between the two methods is shown by the 95% LoA which was from -9.37 to +2.23 mmHg: 53% of the IOP differences fell within +/-3 mmHg. Conclusions: The performance of the ICare tonometer in glaucomatous patients being treated with travaprost 0.004% to lower the IOP appears to be similar to that of young healthy patients. The tendency of ICare to overestimate the IOP readings should be considered when the instrument is used in the follow-up of glaucomatous patients.     

Intraocular pressure and ocular pulse amplitude using dynamic contour tonometry and contact lens tonometry

Background

The new Ocular Dynamic Contour Tonometer (DCT), investigational device supplied by SMT (Swiss Microtechnology AG, Switzerland) allows simultaneous recording of intraocular pressure (IOP) and ocular pulse amplitude (OPA). It was the aim of this study to compare the IOP results of this new device with Goldmann tonometry. Furthermore, IOP and OPA measured with the new slitlamp-mounted DCT were compared to the IOP and OPA measured with the hand-held SmartLens^®, a gonioscopic contact lens tonometer (ODC Ophthalmic Development Company AG, Switzerland).

Methods

Nineteen healthy subjects were included in this study. IOP was determined by three consecutive measurements with each of the DCT, SmartLens^®, and Goldmann tonometer. Furthermore, OPA was measured three times consecutively by DCT and SmartLens^®.

Results

No difference (P = 0.09) was found between the IOP values by means of DCT (mean: 16.6 mm Hg, median: 15.33 mm Hg, SD: +/- 4.04 mm Hg) and Goldmann tonometry (mean: 16.17 mm Hg, median: 15.33 mm Hg, SD: +/- 4.03 mm Hg). The IOP values of SmartLens^® (mean: 20.25 mm Hg, median: 19.00 mm Hg, SD: +/- 4.96 mm Hg) were significantly higher (P = 0.0008) both from Goldmann tonometry and DCT. The OPA values of the DCT (mean: 3.08 mm Hg, SD: +/- 0.92 mm Hg) were significantly lower (P = 0.0003) than those obtained by SmartLens^® (mean: 3.92 mm Hg, SD: +/- 0.83 mm Hg).

Conclusions

DCT was equivalent to Goldmann applanation tonometry in measurement of IOP in a small group of normal subjects. In contrast, SmartLens^® (contact lens tonometry) gave IOP readings that were significantly higher compared with Goldmann applanation tonometer readings. Both devices, DCT and SmartLens^® provide the measurement of OPA which could be helpful e.g. for the management of glaucoma.

     

Comparison of dynamic contour tonometry with goldmann applanation tonometry

PURPOSE: The dynamic contour tonometer (DCT; Pascal tonometer) is a novel tonometer designed to measure intraocular pressure (IOP) independent of corneal properties. The purpose of this study was a comparison of the DCT with the Goldmann applanation tonometer (GAT) with respect to mean of IOP readings, the influence of ocular structural factors on IOP readings, and both intra- and interobserver variability, in a large group of healthy subjects. METHODS: In a prospective study of 228 eyes, IOP measurements by GAT and DCT were compared, and the effects of central corneal thickness (CCT), corneal curvature, axial length, and anterior chamber depth were analyzed. To evaluate intra- and interobserver variability, IOP was measured in eight eyes by four observers. RESULTS: There was a high concordance between the IOP readings obtained by DCT and GAT. However, IOP readings were consistently higher with DCT than with GAT (median difference: +1.7 mm Hg, interquartile range [25th-75th percentile] = 0.8-2.7 mm Hg). In contrast to GAT, multivariable regression analysis showed no significant effect of corneal thickness, corneal curvature, astigmatism, anterior chamber depth, and axial length on DCT readings. For repeated measurements the intraobserver variability was 0.65 mm Hg for the DCT and 1.1 mm Hg for the GAT (P = 0.008). Interobserver variability was 0.44 mm Hg for the DCT and 1.28 mm Hg for the GAT (P = 0.017). CONCLUSIONS: IOP measurements by DCT are highly concordant with IOP readings obtained from GAT but do not vary in CCT and have a lower intra- and interobserver variability. DCT seems to be an appropriate method of tonometry for routine clinical use.     

Agreement of rebound tonometer in measuring intraocular pressure with three types of applanation tonometers

PURPOSE: To evaluate the agreement of iCare rebound tonometer in measuring intraocular pressure (IOP) with Goldmann applanation tonometer (GAT), Tonopen XL, and noncontact tonometer, and the influence of the central corneal thickness (CCT) on IOP measurements made with these four tonometers in 45 (12 control and 33 glaucomatous or ocular hypertensive) eyes. DESIGN: Clinically relevant experimental study. METHODS: Tonometer intermethod agreement was assessed by the Bland-Altman method. The relations of CCT with absolute IOP values and intertonometer differences were analyzed by linear regression. RESULTS: The mean differences (95% limits of agreement) in IOP readings between iCare and GAT, Tonopen XL, and noncontact tonometer were 1.40 +/- 4.29, 0.00 +/- 4.78, and 2.22 +/- 4.19 mm Hg, respectively. All tonometries had a marked association with CCT. As the CCT got thicker, iCare considerably overestimated GAT and Tonopen XL. CONCLUSIONS: Although influenced by CCT, iCare agrees well with applanation tonometers.