Evaluation of the Icare-ONE rebound tonometer as a self-measuring intraocular pressure device in normal subjects

Relationship between Intraocular Pressure Fluctuation and Visual Field Progression Rates in the United Kingdom Glaucoma Treatment Study

PURPOSE

To investigate whether intraocular pressure (IOP) fluctuation is associated independently with the rate of visual field (VF) progression in the United Kingdom Glaucoma Treatment Study.

DESIGN

Randomized, double-masked, placebo-controlled multicenter trial.

PARTICIPANTS

Participants with ≥5 VFs (213 placebo, 217 treatment).

METHODS

Associations between IOP metrics and VF progression rates (mean deviation [MD] and five fastest locations) were assessed with linear mixed models. Fluctuation variables were mean Pascal ocular pulse amplitude (OPA), standard deviation (SD) of diurnal Goldmann IOP (diurnal fluctuation), and SD of Goldmann IOP at all visits (long-term fluctuation). Fluctuation values were normalized for mean IOP to make them independent from the mean IOP. Correlated nonfluctuation IOP metrics (baseline, peak, mean, supine, and peak phasing IOP) were combined with principal component analysis, and principal component 1 (PC1) was included as a covariate. Interactions between covariates and time from baseline modeled the effect of the variables on VF rates. Analyses were conducted separately in the two treatment arms.

MAIN OUTCOME MEASURES

Associations between IOP fluctuation metrics and rates of MD and the five fastest test locations.

RESULTS

In the placebo arm, only PC1 was associated significantly with the MD rate (estimate, -0.19 dB/year [standard error (SE), 0.04 dB/year]; P < 0.001), whereas normalized IOP fluctuation metrics were not. No variable was associated significantly with MD rates in the treatment arm. For the fastest five locations in the placebo group, PC1 (estimate, -0.58 dB/year [SE, 0.16 dB/year]; P < 0.001), central corneal thickness (estimate, 0.26 dB/year [SE, 0.10 dB/year] for 10 μm thicker; P = 0.01) and normalized OPA (estimate, -3.50 dB/year [SE, 1.04 dB/year]; P = 0.001) were associated with rates of progression; normalized diurnal and long-term IOP fluctuations were not. In the treatment group, only PC1 (estimate, -0.27 dB/year [SE, 0.12 dB/year]; P = 0.028) was associated with the rates of progression.

CONCLUSIONS

No evidence supports that either diurnal or long-term IOP fluctuation, as measured in clinical practice, are independent factors for glaucoma progression; other aspects of IOP, including mean IOP and peak IOP, may be more informative. Ocular pulse amplitude may be an independent factor for faster glaucoma progression.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Performance of home-based self-tonometry (iCare HOME (TA022)) for measuring intraocular pressure among healthy and glaucoma patients

Introduction: The purpose of this study was to compare iCare HOME (TA022) with Goldmann applanation tonometer and to evaluate the self-tonometry measurements among the Indian population. Methods: Eligible patients underwent iCare HOME training through guided demonstration (verbal, pictorial, video) and practised self-tonometry measures using iCare HOME. Certification for independent iCare HOME measure was provided if first iCare HOME intraocular pressure (IOP) measurement fell within ± 5 mmHg of Goldmann applanation tonometer (GAT) measurement which was measured by the trained clinician (principal investigator). Certified participants underwent simulated home self-tonometry measurements using iCare HOME, and agreement with GAT IOP measurements was assessed. Results: Seven of 83 participants (8.43%) failed to complete the study due to difficulty in performing the task, leading to non-certification. Patients who could use the iCare HOME had a mean age of 53 ± 15.55years (53% males; 46% females). Only one in 12 subjects did not qualify to use iCare HOME. The overall mean difference between iCare HOME and GAT was 0.83 mmHg (95%, 3.92 and -2.25). At various pressure ranges, 7-16 mmHg, 17-23 mmHg and >23 mmHg, the mean difference between iCare HOME and GAT was 1.22 mmHg (95%, 4.32 and -1.86), 0.77 mmHg (95%,3.69 and -2.19), -0.11 mmHg (95%, 2.52 and -2.74) respectively. The intra-class correlation coefficient of the iCare HOME device was 0.997(95% CI,0.995-0.998). Conclusions: Patients were able to perform self- tonometry using iCare HOME with good reliability and safety. iCare HOME can be used to address the issue of difficulty in acquiring frequent and diurnal IOP measurements by patients doing self-tonometry from home.

How to Measure Intraocular Pressure: An Updated Review of Various Tonometers

Intraocular pressure (IOP) is an important measurement that needs to be taken during ophthalmic examinations, especially in ocular hypertension subjects, glaucoma patients and in patients with risk factors for developing glaucoma. The gold standard technique in measuring IOP is still Goldmann applanation tonometry (GAT); however, this procedure requires local anesthetics, can be difficult in patients with scarce compliance, surgical patients and children, and is influenced by several corneal parameters. Numerous tonometers have been proposed in the past to address the problems related to GAT. The authors review the various devices currently in use for the measurement of intraocular pressure (IOP), highlighting the main advantages and limits of the various tools. The continuous monitoring of IOP, which is still under evaluation, will be an important step for a more complete and reliable management of patients affected by glaucoma.

Initial experience in self-monitoring of intraocular pressure

Background/aims

Diurnal variation in intraocular pressure (IOP) is a routine assessment in glaucoma management. Providing patients the opportunity to perform self-tonometry might empower them and free hospital resource. We previously demonstrated that 74% of patients can use the Icare® HOME tonometer. This study further explores Icare® HOME patient self-monitoring.

Methods

Patients were trained by standard protocol to use the Icare® HOME rebound tonometer. Patient self-tonometry was compared to Goldmann applanation tonometry (GAT) over one clinical day. Following this, each patient was instructed to undertake further data collection that evening and over the subsequent two days.

Results

Eighteen patients (35 eyes) participated. Good agreement was demonstrated between GAT and Icare® HOME for IOPs up to 15 mm Hg. Above this IOP the Icare® tended to over-read, largely explained by 2 patients with corneal thickness >600 um. The mean peak IOP during ‘clinic hours’ phasing was 16.7 mm Hg and 18.5 mm Hg (p = 0.24) over three days. An average range of 5.0, 7.0 and 9.8 mm Hg was shown during single day clinic, single day home and three day home phasing respectively (p =<0.001). The range of IOP was lower in eyes with prior trabeculectomy (6.1 mm Hg vs 12.2 mm Hg). All patients undertook one reading in the early morning at home with an average of 4.8 readings during, and 3.1 readings after office hours.

Conclusions

This small study shows that self-tonometry is feasible. The findings from home phasing demonstrated higher peak and trough IOPs, providing additional clinical information. Home phasing is a viable alternative. The cost-effectiveness of this approach has yet to be addressed.

Comparison between provocative test-based and long-term intraocular pressure parameters in patients with stable open-angle glaucoma

PURPOSE

To compare provocative test-based and long-term intraocular pressure variation parameters in patients with stable open-angle glaucoma.

METHODS

A prospective observational study was carried out in which stable open-angle glaucoma patients (⩾3 years of follow-up without any changes on current medical regimen) were consecutively enrolled. All patients were submitted to a water-drinking test. Long-term intraocular pressure parameters were obtained from isolated intraocular pressure measurements from each visit (⩾5 visits). We investigated the correlation and agreement between the following water-drinking test and long-term intraocular pressure parameters: mean, peak, and fluctuation. In addition, the percentage of eyes with significant intraocular pressure peaks during the water-drinking test (defined as a difference ⩾25% between water-drinking test intraocular pressure peak and mean long-term intraocular pressure) was assessed.

RESULTS

Sixty-three eyes from 63 open-angle glaucoma patients (mean age, 60.7 ± 11.8 years) were included. Mean and water-drinking test intraocular pressure peak correlated significantly with mean (r = 0.67) and maximum long-term intraocular pressure (r = 0.52), respectively (p < 0.01). The correlation between water-drinking test intraocular pressure fluctuation and long-term intraocular pressure fluctuation was not significant (p = 0.45). Limits of agreement from Bland-Altman plots exceeded the maximum allowed difference between methods (3 mm Hg) for all the intraocular pressure parameters analyzed, suggesting poor agreement between water-drinking test-derived and long-term intraocular pressure values. Overall, significant water-drinking test intraocular pressure peaks were observed in 39.7% of these eyes with stable open-angle glaucoma.

CONCLUSION

Although some water-drinking test-based and long-term intraocular pressure parameters correlate significantly, water-drinking test results may not reflect the long-term intraocular pressure profile of stable open-angle glaucoma patients, as their agreement is poor. Many of these patients may experience significant water-drinking test intraocular pressure peaks, despite long-standing stable disease and unchanged medical regimen.

Comparison of Icare Pro Tonometry and Icare One Tonometry Measurements in Healthy Eyes

Objectives

To compare intraocular pressure (IOP) measurements obtained with the Icare Pro tonometer used in clinical practice and the Icare One self-tonometer.

Materials and Methods

Fifty-two eyes of 52 healthy, right-handed individuals with no prior intraocular surgery or ocular trauma, structural ocular pathology, or systemic disease were evaluated. IOP was first measured using the Icare Pro tonometer. The participants were then told how to use the Icare One tonometer and asked to measure their own IOP. The results were analyzed statistically using SPSS v.24.

Results

Of the 52 healthy participants, 16 (30.7%) were male and 36 (69.3%) were female. Their mean age was 31.6±6.3 (23-47) years. Mean IOP measured with the Icare Pro was 17.10±6.2 (11.5-25.2) mmHg, and the mean self-measured IOP with Icare One was 14.01±3.4 (7-24) mmHg. When the two methods were compared using Levene’s t-test, there was a significant mean difference of -3.08±0.6 (95% confidence interval: -4.39 -1.78; p<0.001).

Conclusion

In this study, there was a significant difference between the IOP measurements we made using the Icare Pro and the participants’ self-measured IOP using the Icare One, with the latter being relatively lower. This may be related to the fact that the participants were unfamiliar with using the Icare One. Although the Icare One is a promising tool for glaucoma patients to self-monitor their IOP, further studies are needed.

Icare® rebound tonometers: review of their characteristics and ease of use

The rebound tonometer has a unique mechanism for measuring intraocular pressure (IOP) and has become popular worldwide due to its ease of use. The most notable advantages are the lack of an air-puff and need for topical anesthesia, ease of operation and transport, and the ability to use it with children. Four rebound tonometers (Icare® TA01i, Icare PRO, Icare HOME, and Icare ic100) are currently available for clinical examination. It is important to understand the characteristics of each tonometer and select the most appropriate one because the IOP values and the purpose of measurement are different. In this review, with the goal of improving the understanding of a range of tonometers, the issues with each device are discussed.

Measurement of Intraocular Pressure by Patients With Glaucoma

Importance

The ability of patients to measure their own intraocular pressure (IOP) would allow more frequent measurements and better appreciation of peak IOP and IOP fluctuation.

Objective

To examine whether patients with glaucoma can perform self-tonometry using a rebound tonometer and examine patient acceptability.

Design, Setting, and Participants

An observational study in which IOP was assessed using Goldmann applanation tonometry and a rebound tonometer. Consecutive patients were provided with a patient information sheet and those consenting to take part in the study received standardized self-tonometry training and were then instructed to measure their own IOP under observation. This study was conducted at a glaucoma clinic at a university hospital from March 1, 2016, to December 30, 2016, and included both eyes of 100 patients with glaucoma or ocular hypertension.

Main Outcomes and Measures

The percentage of patients who could successfully perform self-tonometry. Complete success was defined by a good technique and an IOP reading within 5 mm Hg of that obtained by a clinician using the same device. A 3-item questionnaire was used to examine perceptions of self-tonometry among patients.

Results

Among the 100 patients, the mean (SD) age was 67.5 (10.9) years (53% female). A total 73 of 100 patients (73%) met the complete success criteria. An additional 6 patients could use the device but had IOP readings greater than 5 mm Hg different from those obtained by the clinician. On average, IOP by the rebound tonometer was 2.66 mm Hg lower than Goldmann applanation tonometry (95% limits of agreement, -3.48 to 8.80 mm Hg). The IOPs with the rebound tonometer were similar whether obtained by self-tonometry or investigator, with excellent reproducibility with an intraclass correlation coefficient of 0.903 (95% CI, 0.867-0.928). A total of 56 of 79 successful or partially successful patients (71%) felt self-tonometry was easy, with 73 of 79 (92%) reporting self-tonometry to be comfortable, and a similar number happy to perform self-tonometry in the future.

Conclusions and Relevance

Most patients could perform self-tonometry and the method was acceptable to patients. Self-tonometry has the potential to improve patient engagement, while also providing a more complete picture of IOP changes over time.

Monitoring daily intraocular pressure fluctuations with self-tonometry in healthy subjects

PURPOSE

To evaluate the accuracy of the intraocular pressure (IOP) measured by healthy subjects with icare^® Home and to observe the IOP fluctuation and pattern of IOP fluctuation in healthy subjects over three consecutive days.

METHODS

Sixty healthy subjects were recruited to the study. IOP was measured by the subjects themselves and by study staff using icare^® Home tonometers on visits 1 and 2, as well as by study staff using Goldmann applanation tonometry (GAT). Furthermore, the subjects measured their IOP at home for three consecutive days.

RESULTS

Twenty-three per cent of the study eyes were excluded in the statistical analysis due to dropout or non-compliance to the schedule. Approximately 70% of the icare^® Home measurements were within 3 mmHg of the GAT measurements. Ten to 16% of the study eyes had IOP peaks outside office hours. Sixty-three per cent of the study eyes had different IOP patterns on consecutive days.

CONCLUSION

Rebound self-tonometry appears to be accurate and could be used to monitor short- and long-term IOP variations. The difference between IOP patterns on consecutive days raises questions as to the certainty of a single IOP measurement as a measure of treatment effect.

Comparison of self-measured diurnal intraocular pressure profiles using rebound tonometry between primary angle closure glaucoma and primary open angle glaucoma patients

Purpose

To document the diurnal intraocular pressure (IOP) profile with rebound tonometry performed by primary glaucoma patients in non-clinic environment.

Patients and methods

Fifty-three medically-treated eyes of 31 primary angle closure glaucoma (PACG) and 22 primary open angle glaucoma (POAG) patients with no previous eye surgery were recruited. Diurnal IOP was measured 5 times per day at four-hourly intervals from 08:00 to 24:00 for 1 week in patients’ study eye using rebound tonometry in a non-clinic environment. The diurnal IOP profiles were compared between PACG and POAG eyes.

Results

For both PACG and POAG eyes, mean patient-measured IOP was highest in the morning, gradually decreased over the course of a day, and was lowest by midnight (p < 0.001). The diurnal IOP fluctuation ± 1 standard deviation (SD), as documented by SD in daily IOP values, was lower in PACG group (1.6 ± 1.1 mmHg) than in POAG group (2.0 ± 1.2 mmHg; p = 0.049). The mean trough IOP ± 1 SD was higher in PACG group (12.9 ± 2.8 mmHg), compared to POAG group (11.5 ± 3.8 mmHg; p = 0.041). The mean IOP level at midnight ± 1 SD in PACG group (14.0 ± 3.2 mmHg) was higher than that in POAG group (12.1 ± 3.7 mmHg; p = 0.013).

Conclusions

IOP in primary glaucoma patients was highest in the morning, and decreased over the course of a day in non-clinic environment. Treated diurnal IOP fluctuation seemed to be greater in POAG than PACG eyes.

Agreement of patient-measured intraocular pressure using rebound tonometry with Goldmann applanation tonometry (GAT) in glaucoma patients

This study aims to determine the agreement of patient-measured intraocular pressure (IOP) using rebound tonometry with ophthalmologist-measured IOP using Goldmann applanation tonometry (GAT). Fifty-three glaucoma patients used rebound tonometry (Icare ONE, Icare Finland Oy., Finland) to measure their own IOP in ambient environments for 1 week, 5 times per day. Clinic IOP measurements were performed by ophthalmologists using GAT and by patients using rebound tonometry on examination days 1, 4 and 7 of the same week. The agreement between the two tonometries was evaluated by modified Bland-Altman plots and intra-class correlation coefficient (ICC) was determined. Differences in ICCs of them among the three examination days were evaluated by bootstrap resampling analysis. Respective within-measurement ICC of GAT and rebound tonometry were 0.98 and 0.94 on Day 1, 0.98 and 0.93 on Day 4, and 0.96 and 0.92 on Day 7. In a modified Bland-Altman plot, the mean difference ±1 standard deviation (SD) between the two tonometries was 0.15 ± 0.65 mmHg (p = 0.682). Between-measurement ICC were 0.66, 0.76 and 0.73 on the 3 examination days. There was no significant difference among ICCs. In conclusion, patient-measured IOP using rebound tonometry and ophthalmologist-measured IOP using GAT demonstrate good agreement.

Systematic Review of Current Devices for 24-h Intraocular Pressure Monitoring

Glaucoma is a common optic neuropathy that can lead to irreversible vision loss, and intraocular pressure (IOP) is the only known modifiable risk factor. The primary method of treating glaucoma involves lowering IOP using medications, laser and/or invasive surgery. Currently, we rely on in-office measurements of IOP to assess diurnal variation and to define successful management of disease. These measurements only convey a fraction of a patient's circadian IOP pattern and may frequently miss peak IOP levels. There is an unmet need for a reliable and accurate device for 24-h IOP monitoring. The 24-h IOP monitoring devices that are currently available and in development fall into three main categories: self-monitoring, temporary continuous monitoring, and permanent continuous monitoring. This article is a systematic review of current and future technologies for measuring IOP over a 24-h period.

The Icare HOME (TA022) Study: Performance of an Intraocular Pressure Measuring Device for Self-Tonometry by Glaucoma Patients

PURPOSE

To evaluate the Icare HOME (TA022) device (Icare Oy, Vanda, Finland) for use by glaucoma patients for self-tonometry.

DESIGN

Prospective performance evaluation of a medical device.

PARTICIPANTS

One hundred eighty-nine participants with glaucoma or suspected glaucoma were recruited from the Wilmer Eye Institute, Baltimore, Maryland, between July 2014 and April 2015.

METHODS

Participants had standardized training and had to be able use the Icare HOME device independently. Subjects also had to be able to obtain the first intraocular pressure (IOP) measurement within 5 mmHg of Goldmann applanation tonometry (GAT). Those certified obtained 3 IOP measures using the HOME device, and these were compared with Icare TA01i and GAT IOP measurements.

MAIN OUTCOME MEASURES

The agreement between Icare HOME and reference tonometers was used to assess precision. The intraclass correlation coefficient was used to assess within-patient reliability for the HOME device.

RESULTS

Eighteen of 189 recruited patients were ineligible to take part in the study. Forty-four of 171 patients (25.7%) started but failed to complete the study: 7 stopped because of time concerns, 10 of 171 patients (6%) stopped because of difficulty using the device during certification, and 27 of 171 patients (16%) failed to be certified based on IOP. The HOME and GAT measurements agreed within 5 mmHg in 116 of 127 participants (91.3%); 2 participants (1.6%) had a difference of more than 7 mmHg. The mean difference between the Icare HOME and GAT measurements was -0.33 mmHg (standard deviation, 3.11 mmHg). The overall intraclass correlation coefficient for the HOME device was 0.92 (95% confidence interval, 0.89-0.95).

CONCLUSIONS

Not all participants could learn how to use the Icare HOME device, but for those who could, most were able to obtain measurements similar to those obtained by GAT. The Icare HOME device is safe and reliable for self-tonometry, but nearly 1 in 6 individuals may fail to certify in use of the device based on large differences in IOP when comparing GAT with the Icare HOME measurements. The device has the potential to address an unmet need by providing more frequent IOP measurements in a patient's day to day life.

Clinical Evaluation of the New Rebound Tonometers Icare PRO and Icare ONE Compared With the Goldmann Tonometer

PURPOSE

To compare the participant-obtained intraocular pressures (IOPs) using Icare ONE and the clinician-obtained values using Icare PRO, both rebound tonometers, with Goldmann tonometry (GAT) values and analyze the ease of use of Icare ONE.

METHODS

One hundred fifty participants were included (60 normal controls, 90 patients with glaucoma/ocular hypertension). The participants measured the IOP 3 times using Icare ONE; a clinician measured the IOP once using Icare PRO. The instruments were used randomly. Clinical data were evaluated to analyze the difficulty of the technique, the effect on the results, and the ease of use of Icare ONE.

RESULTS

The mean IOPs with GAT, Icare ONE, and Icare PRO were 16.6±4.43, 17.5±5.42, and 16.6±4.77 mm Hg, respectively. The participant-measured IOP values were within +3 mm Hg of the GAT values in 67.1% of eyes with Icare ONE and in 79.6% with Icare PRO. The limits of agreement were higher with Icare ONE compared with Icare PRO. IOP value errors were found with Icare ONE in eyes with low and high GAT-IOP. The areas under the curve to detect IOPs of 21 mm Hg or higher (GAT) exceeded 0.80 with both tonometers. Young participants reported better ease of use with Icare ONE. No other factors were related to the results.

CONCLUSIONS

Icare ONE may be useful for patients monitoring their IOP values; most individuals can use the device after a short training session. Icare PRO had better results compared with Icare ONE in all IOP ranges.

Comparison of Intraocular Pressure Measurements Obtained by Icare PRO Rebound Tonometer, Tomey FT-1000 Noncontact Tonometer, and Goldmann Applanation Tonometer in Healthy Subjects

PURPOSE

To compare intraocular pressure (IOP) measurements obtained by Icare PRO rebound tonometer (RT), Tomey FT-1000 noncontact tonometer (NCT), and Goldmann applanation tonometer (GAT) in healthy subjects, and to investigate the influence of central corneal thickness (CCT) on IOP measurements.

METHODS

A total of 132 eyes of 66 healthy subjects were included in the study. All IOP measurements were applied in a sitting position and always in the same order (RT, NCT, and GAT). CCT was measured by noncontact anterior segment optical coherence tomography.

RESULTS

The mean CCT was 523.5±31.2 μm. The mean IOPs with GAT, NCT, and RT measurements were 14.56±2.77, 13.42±2.99, 14.18±2.55 mm Hg, respectively. A significantly good agreement was found between RT and GAT measurements (P=0.515). The mean difference between RT and GAT measurements was -0.38 mm Hg. An underestimation was found in NCT measurements compared with GAT ones as defined from paired comparisons (P=0.003). The mean difference between NCT and GAT measurements was -1.14 mm Hg. There was no significant difference between NCT and RT readings (P=0.069). The mean difference between NCT and RT measurements was -0.76 mm Hg. There was a significant correlation between GAT-NCT (r=0.740, P<0.001), GAT-RT (r=0.743, P<0.001), NCT-RT (r=0.729, P<0.001) measurement methods. The increment in measured IOP for a 10 μm increase in CCT was 0.16, 0.33, and 0.18 mm Hg for the GAT, NCT, and RT, respectively.

CONCLUSIONS

The IOP readings with the new Icare PRO RT showed good correlation with those obtained by GAT. Tomey FT-1000 NCT underestimated the IOP compared with GAT.

Evaluation of a new rebound tonometer for self-measurement of intraocular pressure

BACKGROUND/AIMS

To compare the accuracy of self-obtained, partner-obtained and trainer-obtained measurements using the handheld Icare Home rebound tonometer with Goldmann applanation tonometry (GAT), and to evaluate the acceptability to subjects of Icare Home measurement.

METHODS

76 subjects were trained to use Icare Home for self-measurement using a standardised protocol. A prespecified checklist was used to assess the ability of a subject to perform self-tonometry. Accuracy of Icare Home self-measurement was compared with GAT using one eye per subject, randomly selected. Bland-Altman difference analysis was used to compare Icare Home and GAT intraocular pressure (IOP) estimates. Acceptability of self-tonometry was evaluated using a questionnaire.

RESULTS

56 subjects (74%, 95% CI 64 to 84) were able to correctly perform self-tonometry. Mean bias (95% limits of agreement) was 0.3 mm Hg (-4.6 to 5.2), 1.1 mm Hg (-3.2 to 5.3) and 1.2 mm Hg (-3.9 to 6.3) for self-assessment, partner-assessment and trainer-assessment, respectively, suggesting underestimation of IOP by Icare Home tonometry. Differences between GAT and Icare Home IOP were greater for central corneal thickness below 500 µm and above 600 µm than data points within this range. Acceptability questionnaire responses showed high agreement that the self-pressure device was easy to use (84%), the reading was quick to obtain (88%) and the measurement was comfortable (95%).

CONCLUSIONS

Icare Home tonometry can be used for self-measurement by a majority of trained subjects. IOP measurements obtained using Icare Home tonometry by self-assessment and third party-assessment showed slight underestimation compared with GAT.

[Ease of handling of first and second generation rebound tonometers]

PURPOSE

To evaluate the ease of handling of two rebound tonometers, which are designed for self-measurement of intraocular pressure (IOP) in a clinical setting by untrained patients.

METHODS

After self-measurement of the IOP with the rebound tonometers iCare ONE and iCare HOME, participants were asked to complete a questionnaire containing different subitems concerning ease of operation using a visual analog scale (1 = very good to 5 = very poor). Moreover, the feasibility and duration of measurement were tested.

RESULTS

A total of 147 subjects participated in this study. The mean score for general handling ability was 2.79 ± 1.01 for the iCare ONE and 1.85 ± 0.87 for the iCare HOME (p < 0.001). The evaluation of the subitems sense of safety (iCare ONE: 2.71 ± 1.03 and iCare HOME: 1.87 ± 0.81, p < 0.001) and comfort of measurement (iCare ONE: 2.07 ± 1.01 and iCare HOME: 1.66 ± 0.72, p < 0.001) also showed a significant discrepancy between the two tonometers. Participants needed significantly less time for a single valid measurement when using the iCare HOME tonometer (mean 66.14 ± 61.54 s) compared to the iCare ONE tonometer (mean 81.54 ± 69.51 s, p < 0.001).

CONCLUSIONS

A better handling of the iCare HOME rebound tonometer in comparison to the iCare ONE tonometer can be deduced on the basis of the subjective assessments of patients and the shorter duration of measurements. Moreover, the iCare HOME received a significantly better evaluation for all subitems. The accuracy of measurements using the iCare HOME still needs to be clarified.

Twenty-four-hour efficacy of preservative-free tafluprost for open-angle glaucoma patients, assessed by home intraocular pressure (Icare-ONE) and blood-pressure monitoring

PURPOSE

To evaluate the effect of preservative-free (PF) tafluprost on diurnal variation of intraocular pressure (IOP) and ocular perfusion pressure (OPP), measured by use of home IOP and blood-pressure (BP) monitoring devices, for primary open angle glaucoma (POAG) patients.

METHODS

Twenty-two eyes from 22 patients with POAG were studied. Initially, IOP was measured at the hospital by Goldmann applanation tonometry (GAT) and Icare-ONE rebound tonometry. Each patient was then instructed how to use the Icare-ONE and BP home monitoring devices. IOP and BP were measured at home by the patients, every 4 h, before and 2 weeks after once daily treatment with PF tafluprost (0.0015%) ophthalmic solution.

RESULTS

Intraclass correlations between different IOP measurements were greater than 0.8. PF tafluprost reduced mean diurnal IOP significantly for patients with POAG, from 15.7 ± 1.2 mmHg at baseline to 12.5 ± 0.6 mmHg 2 weeks after treatment (p < 0.001). It increased mean diurnal OPP from 48.5 ± 7.3 mmHg at baseline to 51.3 ± 7.0 mmHg post-treatment (p < 0.017).

CONCLUSIONS

Icare-ONE enables glaucoma patients to measure their own diurnal IOP fluctuations. Patient-measured Icare-ONE IOP readings showed that PF tafluprost effectively reduced diurnal IOP in eyes with POAG.

Intraocular pressure measurement over soft contact lens by rebound tonometer: a comparative study

AIM

To evaluate the intraocular pressure (IOP) measurements by Icare rebound tonometer over a contact lens in comparison with Goldmann applanation tonometry (GAT).

METHODS

Fifty patients using contact lens were included in this study. One of the eyes of the patients was selected randomly and their IOP were measured by rebound tonometer with and without contact lens (RTCL, RT respectively) and by GAT, as well as their central corneal thickness (CCT) by optical pachymeter. The results of both methods were compared by correlation analysis, general linear method repeated measure and Bland-Altman analysis.

RESULTS

Mean IOP values measured by RTCL, RT and GAT were 15.68±3.7, 14.50±3.4 and 14.16±2.8 (P<0.001), respectively. Mean IOP by RTCL was significantly higher than the measurements implemented by RT and GAT (P<0.001), while there was no difference between the measurements by GAT and RT (P=0.629). There was a good level of positive correlation between GAT and RTCL as well as RT (r=0.786 P<0.001, r=0.833 P<0.001, respectively). We have observed that CCT increase did not show any correlation with the differences of the measurements between RTCL and RT (P=0.329), RTCL and GAT (P=0.07) as well as RT and GAT (P=0.189) in linear regression model.

CONCLUSION

The average of the measurements over contact lens by rebound tonometer was found to be higher than what was measured by GAT. Although this difference is statistically significant, it may be clinically negligible in the normal population.

Teleglaucoma: ready to go?

Telemedicine technologies and services allow today's ophthalmic clinicians to remotely diagnose, manage and monitor several ophthalmic conditions from a distance. But is this the case for glaucomas? There has been a proliferation of telemedicine friendly devices in recent years that improves the capabilities of the clinician in managing glaucomas. The existing instruments still need to align themselves with accepted industry standards. There are successful programmes running in several areas of the world. The safety and efficacy of these programmes needs further exploration. The inability of a single device or test to diagnose glaucomas satisfactorily has also hampered progress in remotely diagnosing these conditions. There is, however, significant potential for telemedicine-friendly devices to remotely monitor the progress of glaucoma and, thereby, reduce some of the workload on an overstretched health service.

Assessment of IcareONE rebound tonometer for self-measuring intraocular pressure

PURPOSE

To evaluate the precision of the IcareONE rebound tonometer, which was developed for self-measuring intraocular pressure (IOP) and to compare IcareONE measurement with Goldmann applanation tonometry (GAT).

METHODS

Twenty-four healthy eyes and 81 glaucomatous eyes were enrolled. IOP measurements (three times per session) with IcareONE were made in a random order by an ophthalmologist (Icare(O)) and by the subject (Icare(S)). Intraclass correlation coefficients (CCs), kappa values and mean values of IOP were compared among the two types of Icare recordings and GAT. Bland-Altman analysis was used to assess agreement between methods. Multiple regression analysis was performed to identify the subject factors that influenced the discordant measurements between IcareONE and GAT.

RESULTS

The mean value of Icare(O) and Icare(S) measurements was 13.5±5.2 and 13.5±5.4 mmHg, respectively, neither of which was significantly different from GAT (13.8±4.4). The intrarater CC of Icare(O) and Icare(S) was 0.968 and 0.885, respectively. The intermethod CC and weighted kappa between Icare(O) and Icare(S) were 0.907 and 0.684, respectively. All pairwise correlations between the two types of IOP measurement showed coefficients of determination >0.8. Bland-Altman analysis did not show any proportional biases. Multiple regression analysis revealed that the differences between GAT and Icare(O) or Icare(S) were positively correlated with central corneal thickness (CCT) and negatively correlated with age.

CONCLUSIONS

Intraocular pressure measurements with IcareONE by a physician and by the subject showed excellent agreement with GAT measurements; IcareONE measurements between a physician and the subject had high intrarater reliability, and good agreement thicker CCT led IcareONE measurement to overestimate IOP, while higher age caused it to underestimate IOP compared with GAT.

Comparative measurement of intraocular pressure by Icare tonometry and Airpuff tonometry in healthy subjects and patients wearing therapeutic soft contact lenses

BACKGROUND

The aim of the present study was to compare the measurement of intraocular pressure (IOP) through a therapeutic soft contact lens with the "native" measurement. We additionally investigate whether a rebound tonometer (RT) or non-contact tonometer (NCT) is more suitable to measure IOP through a bandage contact lens.

METHODS

The IOP was determined using each of the two methods, three times successively with (lens measurement) and without (native measurement) a soft contact lens. The Icare tonometer (Icare® TA01i, Icare Finland Oy, 23 subjects) and the Airpuff tonometer (Nidek NT 53OP, Nidek CO., LTD, Hiroishi Gamagori, Aichi, Japan, 16 subjects) were used. We compared the mean values (validity parameter) and standard deviation (precision parameter) of the three individual measurements in each case using the paired t-test. In addition, we conducted a power analysis to estimate the maximum error in the measurement caused by the contact lens (power level set to 0.8).

RESULTS

With the Airpuff tonometer we detected no statistically significant between the lens and the native measurement (15.6 ± 2.6 vs. 15.3 ± 2.6 mmHg; p = 0.42). The power analysis revealed that the maximum error caused by the contact lens was 1.2 mmHg. The Icare tonometry, however, trended toward higher values in the contact lens measurements (17.5 ± 4.3 vs. 16.4 ± 3.5 mmHg in the native measurements; p = 0.05). Interestingly, this difference exhibited a statistically significant correlation with the corneal thickness (0.03 mmHg per μm corneal thickness; p = 0.04).

CONCLUSION

The use of NCT and RT for IOP measurement over a soft contact lens is feasible. The accuracy appears to be sufficient for the most common clinical applications.

[Comparison of the iCare tonometer with the Goldmann tonometer in Malawi]

BACKGROUND

The risk for glaucoma is 4-5 times higher in patients from sub-Saharan Africa. Thus, especially in developing countries an easy and effective method for assessing the intraocular pressure (IOP) is needed.

METHODOLOGY

In this hospital-based survey 150 eyes were divided into 3 groups concerning the IOP (group I < 16 mmHg, group II 16-23 mmHg and group III > 23 mmHg) and underwent examination with ultrasound pachymetry followed by iCare tonometry (ICT) and Goldmann applanation tonometry (GAT). Agreement of the measurements by two tonometers was assessed with the Bland-Altman method and the influence of the central corneal thickness (CCT) on the ICT measurements was determined.

RESULTS

The mean difference between the IOD measured with GAT and ICT was 0.84 ± 2.63 mmHg. The differences were similar in all three groups (0.77-0.97 mmHg), however, the standard deviation in group III (4.04 mmHg) was greater than in groups I (1.98 mmHg) and II (1.79 mmHg). The mean CCT was 513.51 ± 36.22 µm.

CONCLUSIONS

The agreement of measurements by GAT and ICT was good for lower IOP values but less accurate in patients with higher IOP values (group III). A dependency of the CCT on the ICT measurements was observed. In comparison to other countries the lowest CCTs were found in Malawian patients.