A new rebound tonometer for home monitoring of intraocular pressure

Evaluation of a new transpalpebral tonometer for self-measuring intraocular pressure

PURPOSE

We developed a novel transpalpebral self-tonometer called the TapEye tonometer (TET) based on palpation of the upper eyelid. Our goal was to evaluate a method for improving the accuracy of measuring intraocular pressure (IOP) through the eyelid.

METHODS

Participants underwent standardized training by technicians and were required to be able to use the TET for study inclusion. Subsequently, a noncontact tonometer and Goldmann applanation tonometer (GAT) were used. All participants were instructed to measure their IOPs using the three tonometers at baseline (visit 1) and at 1 month (visit 2). At visit 2, the corrected IOP value measured by the TET (c-TET) was calculated using the difference between the TET and GAT measurements obtained at visit 1.

RESULTS

No significant correlations were found between the TET and GAT measurements at any visit, but the correlation between the c-TET and GAT measurements at visit 2 was significant. The mean difference between the c-TET and GAT measurements was 0.4 ± 3.7 mmHg in the right eye and 0.5 ± 3.4 mmHg in the left eye.

CONCLUSIONS

After correcting the IOP based on the difference between the TET and GAT measurements at the initial visit, the corrected IOP value of the TET was correlated with that of the GAT at the second visit. The TET has the potential to address an unmet need by providing a tool for minimally invasive IOP measurements.

TRIAL REGISTRATION

Clinical trial registration number: jRCTs032220268.

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.

The Utility of iCare HOME Tonometry for Detection of Therapy-Related Intraocular Pressure Changes in Glaucoma and Ocular Hypertension

PURPOSE

To assess whether iCare HOME rebound tonometry can detect therapy-related changes during self-monitoring of intraocular pressure (IOP).

DESIGN

Prospective clinical trial.

PARTICIPANTS

A total of 43 eyes (n = 27 subjects) with open-angle glaucoma or ocular hypertension were enrolled during standard-of-care clinic visits. Participants were grouped into control eyes managed on stable therapy (n = 18 eyes) or therapy change eyes undergoing selective laser trabeculoplasty (SLT, n = 8 eyes), initiating topical therapy (n = 8 eyes), or adding a second medication to existing monotherapy (n = 9 eyes).

METHODS

Subjects recorded IOP 4 times daily for 1 week using iCare HOME tonometry. Upon tonometer return, subjects underwent SLT or new medication start; an additional week of iCare HOME measurements was collected after 4 to 6 weeks. Control subjects recorded an additional week of measurements after 6 weeks. Measurements were grouped into 4 time periods (5-10 am, 10 am to 3 pm, 3-8 pm, 8 pm to 1 am). Goldmann applanation tonometry (GAT) was performed at each study visit for comparison.

MAIN OUTCOME MEASURES

Detection of therapy response defined as an IOP reduction of ≥20%.

RESULTS

For eyes that demonstrated a therapy response by GAT (n = 11), iCare HOME detected a therapy response in 90.9% of eyes in ≥1 time period and 45.5% of eyes in all 4 time periods. In eyes without a GAT-measured therapy response (n = 14), iCare HOME detected a response for 71.4% (n = 10) of eyes in ≥1 time period and for 7.1% of eyes (n = 1) at all 4 time periods. In treatment eyes, intraday and interday average minimum and maximum IOP, as well as interday IOP range, were significantly reduced after therapy without a significant change in intraday IOP range. Control group eyes did not demonstrate a significant change in average IOP minimum, maximum, or range between study weeks.

CONCLUSIONS

Home tonometry with iCare HOME reliably detects therapy-related IOP changes in patients with glaucoma and ocular hypertension. Treatment responses correlated well with in-office GAT and may detect treatment responses missed by GAT. Intraocular pressure measurements via home tonometry provide additional clinical information regarding intraday and interday IOP fluctuation beyond standard of care in office GAT measurements. The iCare HOME is a valuable tool to monitor therapeutic efficacy in patients with 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.

Home monitoring for glaucoma

Glaucoma services are overwhelmed and struggling to accommodate current demand. Reducing the need for hospital based services would improve our ability to see those most at risk of vision loss, which could both reduce demand and improve patient outcomes. Digital technologies that provide opportunities for home monitoring of glaucoma progression have potential to contribute to solve these challenges and, potentially, improve glaucoma care. This article will review the literatures of well-established technologies that support home monitoring for glaucoma, specifically home tonometry (with rebound tonometry) and perimetry with Moorfields Motion Displacement Test and Melbourne Rapid Field.

Analysis of reproducibility, evaluation, and preference of the new iC100 rebound tonometer versus iCare PRO and Perkins portable applanation tonometry

Objectives:

To analyze the reproducibility of the new iC100 rebound tonometer, to compare its results with the applanation tonometry and iCare PRO and to evaluate the preference between them.

Materials and methods:

For the study of reproducibility, 15 eyes of 15 healthy Caucasian subjects were included. Three measurements were taken each day in three separate sessions. For the comparative study, 150 eyes of 150 Caucasian subjects were included (75 normal subjects and 75 patients with glaucoma). Three consecutive measurements were collected with each tonometer, randomizing the order of use. The discomfort caused by each tonometer was evaluated using the visual analogue scale.

Results:

No statistically significant differences were detected between sessions. In the comparison between tonometers, the measurements with iC100 were statistically lower than those of Perkins (−1.35 ± 0.417, p = 0.004) and that iCare PRO (−1.41 ± 0.417, p = 0.002). The difference between PRO and Perkins was not statistically significant ( p = 0.990). The mean time of measurement (in seconds) with iC100 was significantly lower than with Perkins (6.74 ± 1.46 vs 15.53 ± 2.01, p < 0.001) and that PRO (6.74 ± 1.46 vs 11.53 ± 1.85, p < 0.001). Visual analogue scale score with iC100 was lower than Perkins (1.33 ± 0.99 vs 1.73 ± 1.10, p < 0.05). In total, 61.7% preferred iC100 against Perkins.

Conclusion:

The reproducibility of this instrument has been proven good. iC100 underestimates intraocular pressure compared to applanation tonometry at normal values and tends to overestimate it in high intraocular pressure values. Most of the subjects preferred iC100 tonometer.

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.

[Application of rebound self-tonometry for measurements in a supine position]

BACKGROUND

Diurnal or nocturnal fluctuations of intraocular pressure (IOP), which are especially common in glaucoma patients, often require hospitalization of the patient in order to be detected. This is often inconvenient for the patient. Therefore, this study evaluated the usefulness of a rebound tonometer (RT) designed for IOP self-tonometry (RT-Home) in an outpatient department, especially in the supine position and out of office hours.

METHODS

Over a period of 6 months unselected open-angle glaucoma patients were equipped with a RT-home device for one night each. At the beginning IOP values measured by medical personnel (RT-Home(o)) were compared with IOP measured by the patient (RT-Home(p)), as well as measured by applanation tonometry according to Goldmann (GAT). Patients also completed a questionnaire regarding subjective comfort during use of the RT-Home.

RESULTS

The RT-Home(o) showed a bias of -1.1 mm Hg (-7.9 to 5.7 mm Hg) compared to GAT and RT-Home(p) showed a bias of -1.6 mm Hg (-8.9 to 5.9 mm Hg) compared to GAT. The measurement differences between GAT and RT-Home(o) as well as RT-Home(p) showed a stong correlation with the IOP and the central corneal thickness (IOP: r = 0.481, P > 0.0001, RT-Home(o) vs. GAT; corneal thickness: r = 0.612, P < 0.0001, RT-Home(o) vs. GAT). The RT-Home(p) in a supine position showed significantly elevated IOP levels than during the day (P < 0.0001). The RT-Home showed no qualitative differences between measurements in supine and sitting positions.

DISCUSSION

The RT-Home is effective and precise for use in an outpatient department to gain a general overview over patients' IOP out of office hours and also in the supine position. In the long term it seems possible that RT-Home can avoid hospitalization for diurnal and nocturnal IOP evaluation especially of young, mobile patients; however, interpretation of the data always requires professional knowledge.

Self-measurement with Icare HOME tonometer, patients' feasibility and acceptability

PURPOSE

To evaluate and compare the accuracy of self-measurement of intraocular pressure using Icare Home rebound tonometer with Goldmann applanation tonometer and assess acceptability of self-tonometry in patients with glaucoma and ocular hypertension.

METHODS

In the study, 117 subjects were trained to use Icare Home for self-measurement. Icare Home tonometer readings were compared with Goldmann applanation tonometer, including one eye per patient. Agreement between the two methods of measurement was evaluated by Bland and Altmann analysis. Questionnaire was used to evaluate patients' perception of self-tonometry.

RESULTS

One hundred and three out of 117 patients (88%) were able to measure their own intraocular pressure and 96 (82%) fulfilled the requirements for certification. The mean (SD) difference Goldmann applanation tonometer minus Icare Home was 1.2 (2.4) mmHg (95% limits of agreement, -3.4 to 5.9 mmHg). The magnitude of bias between the two methods depended on central corneal thickness, with greater bias at central corneal thickness <500 µm. In 65 out of 96 subjects (67.7%), Icare Home results were within 2 mmHg of the Goldmann applanation tonometer. Seventy-three out of 93 (78.5%) felt that self-tonometry was easy to use and 75 patients (80.6%) responded that they would use the device at home.

CONCLUSION

Icare Home tonometry tends to slightly underestimate intraocular pressure compared to Goldmann applanation tonometer. Most patients were able to perform self-tonometry and found it acceptable for home use. Measurements using rebound self-tonometry could improve the quality of intraocular pressure data and optimize treatment regimen.

Diurnal Intraocular Pressure Fluctuations with Self-tonometry in Glaucoma Patients and Suspects: A Clinical Trial

SIGNIFICANCE

This article shows that self-tonometry can provide robust measures of diurnal intraocular pressure (IOP) and also detect changes to IOP in response to treatment within a short period of monitoring. These advances in IOP monitoring may contribute to improved management of glaucoma patients and suspects.

PURPOSE

The aim of this study was to prospectively investigate the utility of rebound self-tonometry performed over several weeks for detecting diurnal IOP fluctuations in glaucoma patients and suspects and also initial response to topical treatment in glaucoma patients.

METHODS

Forty patients were recruited following glaucoma-specific examination. Subsequent to successful training with the iCare HOME tonometer, patients were instructed to measure IOP, in a sitting position, four times a day over 4 to 6 weeks. Date, time, laterality, and IOP downloaded from the tonometer and clinical examination data, including applanation IOP and corneal thickness, were analyzed. A user satisfaction survey was also administered at study completion. t Test and analysis of variance were used to compare groups and IOP across days. Pearson correlation was used to compare measurements to Goldmann applanation tonometry and IOP measurements from the first day/s to the overall mean IOP.

RESULTS

Twenty-seven patients (18 suspects and 9 glaucoma patients) completed data collection. Patients self-measured IOP on 118 (±29) occasions for 40 (±7.4) days. Two dominant patterns of fluctuation were revealed: peak IOP upon awakening (n = 11) and at midday (n = 13). Diurnal IOP measured in the first 7 days showed strong correlation to diurnal IOP across the entire study period (r = 0.82, P < .0001). Within 24 hours of treatment commencement (latanoprost 0.005% ophthalmic solution), IOP reduced from 23.9 (±5.2) to 16.1 (±2.6) mmHg. Overall, patients rated the instrument as easy to use, although difficulties with correct alignment were expressed.

CONCLUSIONS

Rebound self-tonometry demonstrated utility for measuring diurnal IOP fluctuations in most patients, hence enhancing management of patient with or at risk of developing glaucoma.

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.

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.

Comparison of intraocular pressure measurements with different contact tonometers in young healthy persons

AIM

To analyze the correlation of Goldmann applanation tonometer (GAT), I-Care tonometer and Tono-Pen tonometer results in young healthy persons, and to investigate the influence of central corneal thickness (CCT) on intraocular pressure (IOP) measurements recorded with these tonometers.

METHODS

We conducted a pilot clinical study in 78 eyes of 78 subjects aged 22-28 years old (44 women and 34 men; mean age 23.8±1.19y). IOP was measured using GAT, I-Care and Tono-Pen tonometers, followed by measurements of CCT. Statistical analysis was performed using SPSS 20.0.

RESULTS

The mean IOPs and standard deviation (±SD) for GAT, I-Care and Tono-Pen were 15.62±2.281 mm Hg, 16.29±2.726 mm Hg and 16.32±2.393 mm Hg, respectively. The mean CCT was 555.15±29.648 µm. Clear positive correlations between GAT and I-Care, GAT and Tono-Pen, and I-Care and Tono-Pen tonometers were found (r=0.867, P<0.001; r=0.861, P<0.001; r=0.915, P<0.001, respectively). In comparison between devices, Bland-Altman analysis showed a significant mean difference (MD) in the measurements by GAT and I-Care of -0.679 mm Hg and by GAT and Tono-Pen of -0.705 mm Hg ( P<0.001), but there was no significant difference between I-Care and Tono-Pen ( P>0.05). Both non-gold standard tonometers were affected by CCT; that is, both I-Care and Tono-Pen tonometer values were significantly higher with higher CCT means (>555 µm; MD=-1.282, P<0.001; MD=-0.949, P<0.001, respectively) compared with GAT.

CONCLUSION

Both I-Care and Tono-Pen tonometers overestimated IOP compared with the GAT values. Either the I-Care or Tono-Pen tonometer could be used instead of GAT because there was no significant difference between their results. Higher CCT values (>555 µm) were associated with overestimated IOP values.

Intradevice and Interdevice Agreement Between a Rebound Tonometer, Icare PRO, and the Tonopen XL and Kowa Hand-held Applanation Tonometer When Used in the Sitting and Supine Position

PURPOSE

The aim of the study was to investigate the agreement between a new portable tonometer, Icare PRO, and the Tonopen XL and Kowa hand-held applanation tonometers (HAT).

METHODS

The right eyes of 127 healthy subjects were enrolled. Intraocular pressure (IOP) was measured in both sitting and supine positions using the Icare PRO, Tonopen XL, and Kowa HAT tonometers. The repeatability of the IOP measurements was evaluated by calculating intraclass correlation coefficients. Between-method agreements of tonometer measurements were evaluated using Bland-Altman analysis.

RESULTS

Intradevice agreement: The intraclass correlation coefficients (sitting, supine) of Icare PRO, Tonopen XL, and Kowa HAT were (0.863, 0.656), (0.845, 0.819), and (0.957, 0.956), respectively.Interdevice agreement: The Bland-Altman analysis revealed that, in the sitting position, the mean differences between Icare PRO and Tonopen XL, and between Icare PRO and Kowa HAT were -0.43 and 0.43 mm Hg, respectively (95% limits of agreement: -6.24 to 5.34 mm Hg, -4.04 to 4.90 mm Hg). In the supine position, the corresponding mean differences were -0.88 and 0.14 mm Hg (95% limits of agreement: -5.66 to 3.91 mm Hg, -4.06 to 4.33 mm Hg). IOP differences between Icare PRO and the other tonometers were unaffected by central corneal thickness.

CONCLUSIONS

The repeatability of Icare PRO was slightly lower in the supine position than in the sitting position. Although Icare PRO underestimated IOP values in eyes with higher IOP when compared with Tonopen XL and Kowa HAT in both positions, we observed good interdevice agreement between Icare PRO and both Tonopen XL and Kowa HAT.

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.

Noninvasive intraocular pressure monitoring: current insights

Glaucoma is the second leading cause of blindness worldwide and intraocular pressure (IOP) is currently its only modifiable risk factor. Peak IOP has for a long time been considered as a major contributor to glaucoma progression, but its effects may depend not only on its magnitude, but also on its time course. The IOP is nowadays considered to be a dynamic parameter with a circadian rhythm and spontaneous changes. The current practice of punctual measuring the IOP during office hours is therefore a suboptimal approach, which does not take into account the natural fluctuation of IOP. Because of its static nature a single IOP measurement in sitting position fails to document the true range of an individual's IOP, peak IOP, or variation throughout the day. Phasing means monitoring a patient's IOP during the daytime or over a 24-hour period. This can provide additional information in the management of glaucoma patients. This review focuses on the current insight of non-invasive IOP monitoring as a method of obtaining more complete IOP profiles. Invasive techniques using an implantable sensor are beyond the scope of this review.

[Rebound tonometry after vitreoretinal surgery]

PURPOSE

The aim of this study was to analyze the practicability and comparability of the Icare rebound tonometer (RT) versus the Schiötz indentation tonometer (SIT) and the Goldmann applanation tonometer (GAT) for measuring intraocular pressure (IOP) in patients after pars plana vitrectomy (PPV).

METHODS

A total of 100 eyes from 100 patients who underwent vitreoretinal surgery in the Department of Ophthalmology, University of Cologne were included in this prospective analysis. The IOP was measured using RT preoperatively, on the day of surgery and 2 days after surgery, using SIT on the day of surgery and GAT preoperatively and 2 days after surgery. For the evaluation eyes were divided into subgroups with respect to the endotamponade selected and the IOP level.

RESULTS

The mean preoperative IOP for all enrolled eyes was 15.4 ± 8.0 mmHg for RT and 16.1 ± 7.9 mmHg for GAT. Bland-Altman analysis revealed a bias between RT and GAT of - 0.6 mmHg. Bland-Altman analysis for the postoperative course of all eyes revealed a bias of 3.0 mmHg between RT and SIT on the day of surgery and no bias between RT and GAT in the further postoperative follow-up.

CONCLUSION

Rebound tonometry seems to provide precise IOP values after vitreoretinal surgery. Divergence from SIT values on the day of surgery is presumably due to a general tendency of SIT to underestimate IOP values. Therefore, RT can be used in the clinical routine after vitreoretinal surgery as an alternative to GAT.

Clinicians' perspectives on the use of drug-eluting contact lenses for the treatment of glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. The perspective of clinicians who treat the disease is important and may ultimately dictate the adoption of new treatment modalities, such as drug-eluting contact lenses. Recent advances have enabled contact lenses to serve as a sustained-release drug-delivery platform capable of treating glaucoma. This review covers the medical treatment of glaucoma, suboptimal adherence rates to treatment, and factors that may influence the clinical applicability of drug-eluting contact lenses. Ophthalmologists who treat glaucoma were surveyed to determine their perspective on treatment adherence, bandage contact lens use and the use of a drug-eluting contact lens to treat glaucoma. Given the challenge of treating glaucoma and the clinical need for improved drug delivery, drug-eluting contact lenses appear to be a promising treatment option.

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.

[Evaluation of the self-tonometer Icare ONE in comparison to Goldmann applanation tonometry]

OBJECTIVE

The aim of this clinical study was to demonstrate the practicability of self-measured intraocular pressure and to evaluate the reliability by comparing the data with those obtained by Goldmann applanation tonometry (GAT).

METHODS

A total of 40 patients aged between 44 and 82 years with glaucoma were introduced to the handling of the tonometer. The self-measurements were done for 1-3 days following the medical measurement by GAT. The data were saved as "correct" or in the case of wrong handling as "false". The impressions of the patients were obtained by a questionnaire.

RESULTS

A total number of 191 single measurements were registered by the Icare ONE and of these there were 97 (50.8%) signed "false". Of the patients 45% reached a maximum difference of ±5 mmHg between GAT and self-measurement in every single measurement. In the subgroup of under 60-year-old patients 70% reached this result. There were no indications of a systematic error. Of the probands 60% considered the handling of the Icare ONE as difficult. Nevertheless, 80% could imagine using the self-tonometer at home.

CONCLUSIONS

The differences between the self-measurements and the GAT were highly fluctuating in some cases. In the group of patients younger than 60 years the agreement was better, so problems with the handling of the Icare ONE may be an important factor. However, the acceptance in the patients tested was high and continuous pressure measurements at home could be reasonable. Advancements in the handling and reliability are needed to improve clinical application of the measured values.

Icare ONE rebound versus Goldmann applanation tonometry in children with known or suspected glaucoma

PURPOSE

To compare Icare ONE tonometry by clinic examiner and parent/guardian to Goldmann applanation in children with known/suspected glaucoma; to evaluate the trend in intraocular pressure (IOP) with 4 repeated measurements using Icare ONE; and to evaluate the feasibility of instructing parents on the use of the Icare ONE device in the clinic setting.

DESIGN

Nonrandomized, prospective clinical study.

METHODS

Patients with known or suspected glaucoma were recruited from the Duke pediatric glaucoma clinic. Parent(s) of all subjects gave informed consent (and children gave assent) for participation in this research study. IOP was measured using Icare ONE by clinic examiner and parent/guardian, then using Goldmann applanation (masked physician). Each parent/guardian completed an ease-of-use survey.

RESULTS

Sixty eyes (60 children) were included. Absolute value of mean IOP difference (ICare ONE clinic examiner vs Goldmann applanation) was 3.3 ± 4.0 mm Hg (P = .001). Icare ONE IOP by clinic examiner was within 3 mm Hg of Goldmann applanation in 68% (n = 41 eyes). In eyes with >3 mm Hg difference, Icare ONE was higher than Goldmann applanation in 84%. IOP demonstrated a statistically significant downward trend with repeated sequential measurements with Icare ONE (P = .0053, r(2) = 0.9894). All parents accomplished Icare ONE tonometry on at least 1 eye; 98% reported it was "easy to learn to use."

CONCLUSION

Icare ONE tonometry appears accurate and well-tolerated compared to Goldmann applanation, and holds promise for clinic and home tonometry in children. IOP trends downward with successive measurements using Icare ONE, demonstrating a possible effect from presumed patient relaxation.