The Clinical Interpretation of Changes in Intraocular Pressure Measurements Using Goldmann Applanation Tonometry: A Review

The relationship between intraocular pressure and glaucoma: An evolving concept

Intraocular pressure (IOP) is the most important modifiable risk factor for glaucoma and fluctuates considerably within patients over short and long time periods. Our field's understanding of IOP has evolved considerably in recent years, driven by tonometric technologies with increasing accuracy, reproducibility, and temporal resolution that have refined our knowledge regarding the relationship between IOP and glaucoma risk and pathogenesis. The goal of this article is to review the published literature pertinent to the following points: 1) the factors that determine IOP in physiologic and pathologic states; 2) technologies for measuring IOP; 3) scientific and clinical rationale for measuring diverse IOP metrics in patients with glaucoma; 4) the impact and shortcomings of current standard-of-care IOP monitoring approaches; 5) recommendations for approaches to IOP monitoring that could improve patient outcomes; and 6) research questions that must be answered to improve our understanding of how IOP contributes to disease progression. Retrospective and prospective data, including that from landmark clinical trials, document greater IOP fluctuations in glaucomatous than healthy eyes, tendencies for maximal daily IOP to occur outside of office hours, and, in addition to mean and maximal IOP, an association between IOP fluctuation and glaucoma progression that is independent of mean in-office IOP. Ambulatory IOP monitoring, measuring IOP outside of office hours and at different times of day and night, provides clinicians with discrete data that could improve patient outcomes. Eye care clinicians treating glaucoma based on isolated in-office IOP measurements may make treatment decisions without fully capturing the entire IOP profile of an individual. Data linking home blood pressure monitors and home glucose sensors to dramatically improved outcomes for patients with systemic hypertension and diabetes and will be reviewed as they pertain to the question of whether ambulatory tonometry is positioned to do the same for glaucoma management. Prospective randomized controlled studies are warranted to determine whether remote tonometry-based glaucoma management might reduce vision loss and improve patient outcomes.

Evaluation of agreement of IOP measurements by Tono-Vera tonometer to Goldmann applanation tonometry

Purpose

To evaluate the accuracy of the new Tono-Vera rebound tonometer (Reichert Inc, Buffalo, NY) compared to Goldmann Applanation Tonometry.

Methods

This prospective, observational, cross-sectional study was designed in accordance with ANSI Z80.10-2014 and ISO 8612-2009 guidelines for tonometer comparison. Intraocular Pressure (IOP) was measured by Goldmann Applanation and Tono-Vera on 160 eyes of 160 subjects. Corneal Astigmatism and Central Corneal Thickness were also measured. A single investigator (CN) conducted all measurements. The average of two measurements from each tonometer was used in the analysis. Bland-Altman plots, total least squares regression analysis, and simple linear regression were used to evaluate agreement between the tonometers.

Results

Average IOP values from Goldmann Applanation and Tono-Vera were not significantly different (19.17 and 19.03 respectively, p=0.40, paired t-test). The total least squares regression analysis indicated strong agreement between the two tonometers (slope +0.97, offset +0.49 mmHg, standard deviation 2.11 mmHg). There were 2 IOP measurement pairs that exceeded the ± 5 mmHg limits of agreement required in ANSI Z80.10-2014 and ISO 8612-2009, which is within the range of acceptability specified in the standards.

Conclusion

We evaluated IOP measurements by Tono-Vera Rebound Tonometer vs Goldmann Applanation Tonometry for eyes with a wide range of IOP values and found no statistically significant differences in the results. Tono-Vera meets the requirements of ANSI Z80.10-2014 and ISO 8612-2009, demonstrating accuracy comparable to Goldmann tonometry.

Exploring the Spectrum of VEGF Inhibitors' Toxicities from Systemic to Intra-Vitreal Usage in Medical Practice

The use of Vascular Endothelial Growth Factor inhibitors (VEGFi) has become prevalent in the field of medicine, given the high incidence of various pathological conditions necessitating VEGF inhibition within the general population. These conditions encompass a range of advanced neoplasms, such as colorectal cancer, non-small cell lung cancer, renal cancer, ovarian cancer, and others, along with ocular diseases. The utilization of VEGFi is not without potential risks and adverse effects, requiring healthcare providers to be well-prepared for identification and management. VEGFi can be broadly categorized into two groups: antibodies or chimeric proteins that specifically target VEGF (bevacizumab, ramucirumab, aflibercept, ranibizumab, and brolucizumab) and non-selective and selective small molecules (sunitinib, sorafenib, cabozantinib, lenvatinib, regorafenib, etc.) designed to impede intracellular signaling of the VEGF receptor (RTKi, receptor tyrosine kinase inhibitors). The presentation and mechanisms of adverse effects resulting from VEGFi depend primarily on this distinction and the route of drug administration (systemic or intra-vitreal). This review provides a thorough examination of the causes, recognition, management, and preventive strategies for VEGFi toxicities with the goal of offering support to oncologists in both clinical practice and the design of clinical trials.

EYEMATE-SC Trial: Twelve-Month Safety, Performance, and Accuracy of a Suprachoroidal Sensor for Telemetric Measurement of Intraocular Pressure

PURPOSE

Measuring and controlling intraocular pressure (IOP) provide the foundation for glaucoma treatment. Self-tonometry has been proposed as an alternative to measure IOP throughout the entire day better. The novel EYEMATE-SC sensor (Implandata) is implanted in the suprachoroidal space to enable contactless continual IOP monitoring. The aim of the present study was to investigate the 1-year safety, performance, and accuracy of the EYEMATE-SC in patients with primary open-angle glaucoma undergoing simultaneous nonpenetrating glaucoma surgery (NPGS).

DESIGN

Prospective, multicenter, open-label, single-arm, interventional clinical trial.

PARTICIPANTS

Twenty-four eyes of 24 patients with primary open-angle glaucoma who were due to undergo NPGS (canaloplasty or deep sclerectomy).

METHODS

An EYEMATE-SC sensor was implanted during NPGS. Goldmann applanation tonometry (GAT) measurements were compared with the sensors' IOP measurements at all postoperative visits through 12 months.

MAIN OUTCOME MEASURES

Device position and adverse events.

RESULTS

Fifteen eyes underwent canaloplasty, and 9 underwent deep sclerectomy. Successful implantation of the sensor was achieved in all eyes with no reported intraoperative difficulties. Through the 12-month follow-up, no device migration, dislocation, or serious device-related complications were recorded. A total of 536 EYEMATE-SC measurements were pairwise included in the IOP agreement analysis. The overall mean difference between GAT and EYEMATE-SC measurements was 0.8 mmHg (95% confidence interval [CI] of the limits of agreement [LoA], -5.1 to 6.7 mmHg). The agreement gradually improved, and from 3 months after surgery until the end of the follow-up, the mean difference was -0.2 mmHg (95% CI of LoA, -4.6 to 4.2 mmHg) over a total of 264 EYEMATE-SC measurements, and 100% of measurements were within ±5 mmHg of GAT.

CONCLUSIONS

The EYEMATE-SC sensor was safe and well tolerated through 12 months. Moreover, it allowed accurate, continuous IOP monitoring.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

How should we measure intraocular pressure in the era of coronavirus disease 2019? Balancing infectious risk, cleaning requirements, and accuracy

PURPOSE OF REVIEW

Accurate and precise measurement of intraocular pressure (IOP) is a vitally important component of the ophthalmic examination. There are multiple methods of tonometry, each of which has considerations in light of the ongoing severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic. This review discusses these considerations and compares various tonometer methods with the gold standard of Goldmann applanation tonometry (GAT).

RECENT FINDINGS

The SARS-CoV-2 virus may spread via droplets, microaerosols, or direct contact in the ophthalmology clinic. Tonometry poses a high risk of contamination. The accuracy and reliability of various methods of tonometry with single-use disposable equipment has been compared with Goldmann applanation tonometry.

SUMMARY

Goldmann applanation tonometry with disposable applanation tips, Tono-pen, and iCare employ single use tips to decrease the risk of cross-contamination of infectious agents. Review of the literature demonstrates good correlation between these devices and GAT, although the published level of agreement between devices varies.

Modification of Corneal Biomechanics and Intraocular Pressure Following Non-Penetrating Deep Sclerectomy

Changes in the cornea can influence outcomes in patients with primary open-angle glaucoma (POAG). We aimed to evaluate the relevance of changes in corneal biomechanics and intraocular pressure (IOP) in patients undergoing non-penetrating deep sclerectomy (NPDS) with the Esnoper V2000 implant^® (AJL Ophthalmic S.A., Gasteiz, Spain). We included 42 eyes of 42 patients with POAG scheduled for NPDS with the Esnoper V2000 implant. Biomechanical properties were measured by Ocular Response Analyzer^® G3 (ORA; Reichert Inc., Depew, NY, USA). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal compensated IOP (IOPcc), and Goldmann-correlated IOP (IOPg) were measured the day before surgery and on day 1, 7, and 30 and 2 and 3 months after surgery. CH initially increased, fell below the presurgical value at 30 days after the surgery, and increased again at 2 and 3 months. CRF, IOPcc, and IOPg decreased on the first day after surgery, then followed a trend of increasing but stayed below pre-surgery levels. All values reached statistical significance. While observed changes in corneal biomechanics after NPDS and Esnoper V2000 implant were significant, more studies are needed if we are to understand their influence on corneal biomechanics and their clinical relevance in POAG.

Repeatability, reproducibility, and agreement of three tonometers for measuring intraocular pressure in rabbits

The aim of this study was to evaluate repeatability, reproducibility, and agreement of three commonly used tonometers in animal research (TonoLab, TonoVet, and TonoPEN AVIA) in a cohort of 24 rabbits. Additionally, the impact of sedation on IOP was investigated in 21 New Zealand White rabbits with the TonoVet tonometer. Repeatability was determined using the coefficient of variation (CoV) for two observers. For the TonoLab (6.55%) and TonoVet (6.38%) the CoV was lower than for the TonoPEN AVIA (10.88%). The reproducibility was highest for the TonoVet (0.2 ± 3.3 mmHg), followed by the TonoLab (0 ± 12.89 mmHg) and lowest for the TonoPEN AVIA (− 1.48 ± 10.3 mmHg). The TonoLab and TonoVet showed the highest agreement (r = 0.85, R² = 0.73). After sedation, a significant IOP reduction (often > 25%) was observed. Our results show that among the three tonometers tested, the TonoVet tonometer is best for use in rabbits while the TonoLab should be avoided. The impact of sedation on IOP was substantial and should be taken into account during experimentation.

Influence of mental stress on intraocular pressure and visual field testing: is there a white coat syndrome in glaucoma?

PURPOSE

To investigate the effects of mental stress stimulus on intraocular pressure (IOP) measurement and visual field (VF) testing.

METHODS

Patients with open angle glaucoma underwent a baseline IOP measurement and VF testing. Afterwards, they completed a computerized mental stress test (Stroop test) which is a known standardized method to induce mental stress. After test completion, patients underwent a second IOP measurement and VF testing.

RESULTS

Seventy-two eyes of 36 patients were enrolled. Mean age was 67.0 ± 9.5 years (range 47-84 years). The mean baseline IOP was 15.0 mmHg, and after the Stroop mental stress test, IOP increased to 16.0 mm Hg (P < 0.001). There was a trend towards significant mean deviation decreased from -6.9 dB to -8.0 dB (P = 0.054, t-test) following the stress test. This difference became significant using the Wilcoxon nonparametric test (P = 0.008). Correlation was found between glaucoma severity and change in IOP (P = 0.02) and PSD (P < 0.01).

CONCLUSIONS

We found a small but statistically significant increase in IOP and a trend towards deterioration of visual field mean deviation, following a short mental stress test. Patients with more severe glaucoma showed more pronounced changes. Our results suggest that mental stress could affect IOP measurement in the clinic.

Diurnal variation of corneal elasticity in healthy young human using air-puff optical coherence elastography

Due to the disruption of intraocular pressure (IOP) and central corneal thickness (CCT), diurnal variation in normal young human corneal elasticity is not clear. Using the custom-built air-puff optical coherence elastography, one eye of 21 normal subjects is enrolled randomly to measure the central corneal elasticity, IOP, and CCT in different time points within a day. Based on the multi-level model, the corneal elastic modulus is found to have a linear positive relation with IOP (P < .01) but not CCT (P = .175) and time point (P = .174-.686). A new indicator, corneal elasticity change rate, is proposed to present the magnitude of corneal elasticity change caused by 1 mmHg IOP, which can correct the interference effect of IOP. The results show that the corneal elasticity in the normal young human does not have the characteristics of diurnal variation under IOP control. Furthermore, IOP plays an important role in the corneal elasticity, and corneal elasticity change rate can increase the comparability of results between individuals.

Continuous 24-hour measurement of intraocular pressure in millimeters of mercury (mmHg) using a novel contact lens sensor: Comparison with pneumatonometry

PURPOSE

To address the unmet need of continuous IOP monitoring, a Pressure-Measuring Contact Lens (PMCL) was developed to measure IOP in millimeters of mercury (mmHg) continuously over 24 hours. The present study assessed the reliability of the novel PMCL.

METHODS

In this prospective open-label clinical study, healthy and open-angle glaucoma (OAG) subjects were fitted with the PMCL, and pneumatonometry was performed on study eyes (in absence of the PMCL) and on fellow eyes before, during, and after provocative tests. The primary outcome measures were (1) mean IOP difference between same-eye measurements, and (2) percentage of timepoints at which IOP measured by the PMCL was within 5 mmHg of that measured by pneumatonometry in the fellow eye.

RESULTS

Eight subjects were analysed (4 healthy, 4 OAG). The average difference in successive IOP measurements made by pneumatonometry and with the PMCL was 2.0±4.3mmHg at placement-time, and 6.5±15.2mmHg at removal time. During water drinking test, a significant increase in IOP was detected both by PMCL in the study eye (2.4±2.5mmHg, p = 0.03) and by pneumatonometry in the fellow eye (1.9±1.9mmHg, p = 0.02). Over the 24-hour recording, 88.0% of IOP variations measured by the PMCL were within 5mmHg of that measured with the pneumatonometer in the fellow eye. A transient corneal erosion of severe intensity was observed following removal of the PMCL on one single eye, and may have affected measurement accuracy in that eye.

CONCLUSIONS

This study is a proof-of-concept for this novel PMCL, and its results are encouraging, with a fair accuracy in IOP values measurement and good sensitivity to subtle IOP variations.

Relationship Between Contact Lens Sensor Output Parameters and Visual Field Progression in Open-angle Glaucoma: Assessment of a Practical Tool to Guide Clinical Risk-assessment

PURPOSE

In recent years, new technologies have emerged to better analyze and interpret intraocular pressure (IOP) fluctuations. Among them is the progression report (PR), an algorithm based on continuous contact lens sensor (CLS) readings to estimate the likelihood of fast visual field (VF) glaucomatous progression. The objective of this study is to validate the PR.

METHODS

In this retrospective study, 30 open-angle glaucoma patients were enrolled. Twenty-four hours IOP-related variations were recorded using a CLS. Recordings were used to generate PR. The likelihood of fast VF progression (<-1 dB/y mean deviation) was estimated by 2 masked assessors based on clinical parameters. At least 3 VF were performed over the 2 years following the initial assessment, to determine actual progression.

RESULTS

Mean age was 65.9±10.45 years, with a mean baseline mean deviation of -5.4±5.1. After a mean follow-up of 29.5±12.9 months, 26.7% of eyes were assessed as fast progressors (-2.9±1.9 dBs/y). The average risk-score attributed by the PR was 42% [41% (slow) vs. 44% (fast); P=0.035]. Correlations between the 2 assessors were good (r=0.59), and identical to that between PR and the averaged assessors' gradings. Correlations between mean deviation progression rates and PR, Assessor 1 and Assessor 2's gradings were, r=0.57, 0.31, and 0.43, respectively.

CONCLUSIONS

PR provided comparable predictions of the risk of fast VF progression as did physician estimates based on all available clinical data. With their relationship to the eye's biomechanical properties and the ocular tissues' response to pressure variations, CLS recordings may offer new information that complements conventional examinations.

Evaluating Goldmann Applanation Tonometry Intraocular Pressure Measurement Agreement Between Ophthalmic Technicians and Physicians

PURPOSE

To examine IOP measurement disagreement between technicians and physicians and the impact of an educational intervention on the short and long-term disagreement in IOP measurement using Goldmann applanation tonometry.

DESIGN

Prospective study designed to enhance measurement reliability.

SETTING

A glaucoma clinic at a university hospital. StudyPopulation: 6 technicians and 2 physicians.

INTERVENTION

An educational intervention was implemented for the technicians to improve IOP measurement agreement with physicians. MainOutcomeMeasures: Frequency of IOP measurement disagreement between physicians and technicians, defined as a difference in IOP of >2 or >3 mm Hg and assessed at baseline and immediately and 6 months postintervention.

RESULTS

IOP was evaluated for a total of 529 eyes (physician measured mean IOP = 16.4 mm Hg [SD = 5.9]), 30 per technician-physician pair for each data collection period: baseline, immediately postintervention and 6 months postintervention. At baseline, physicians disagreed 17% and 7% of the time when measuring IOP using >2 and >3 mm Hg to define disagreement, respectively, whereas the average disagreement between technicians and physicians was 25% and 13%. Disagreement was greater at IOPs greater than 20 mm Hg. No significant changes were noted in the frequency of disagreement between technicians and physicians immediately or 6 months postintervention.

CONCLUSIONS

Two physicians measuring the same patient in the same room disagreed by >2 mm Hg in 17% of patients' eyes, and this amount of disagreement was even higher when comparing physicians to certified technicians. An educational intervention did not improve agreement in IOP measurements between technicians and physicians. This highlights an important limitation of Goldmann tonometry.

Minimally Invasive Surgery, Implantable Sensors, and Personalized Therapies

Glaucoma management has changed dramatically over the last decades, through clinical advances and technological revolutions. This review discusses the latest innovations and challenges faced in the field around three major axes: minimally-invasive glaucoma surgery (MIGS), implantable sensors and injectable therapeutics. Indeed, the vast number of recently developed MIGS techniques has not only provided clinicians with a wide range of therapeutic options, but they have also enabled them to adjust their therapies more finely which may have contributed a more patient-centric decision-making process. Yet, despite considerable advances in the field, the wide heterogeneity in clinical trial designs blurs the surgical outcomes, specificities and indications. Thus, more high-quality data are required to make the choice of a specific MIGS procedure more than an educated guess. Beyond the scope of MIGS, the potential of IOP telemetry for self-assessment of IOP-control through implantable sensors is developing into a real option for clinicians and an empowering opportunity for patients. Indeed, providing patients with direct feedback enables them to take control and have a clearer representation of their care, in turn leading to a better control of the disease. However, there are potential issues with self-monitoring of IOP, such as increased anxiety levels induced by measured IOP fluctuations and peaks, leading to patients self-treating during IOP spikes and additional office visits. Furthermore, the advent of implantable therapeutics may soon provide yet another step towards personalized glaucoma treatment, by offering not only an efficient alternative to current treatments, but also a therapeutic option that may better adapt to patients' lifestyle. After several decades of relative stagnation through the last century, glaucoma has now entered what many view as a golden age for the specialty. Like every revolution, this one brings its fair share of uncertainty, clinical questioning and uneasy periods of adaptation to ever-changing expectations. Yet, while it is impossible to guess what the landscape of glaucoma surgery will be like in ten or fifteen years, data suggest a bright outlook both for patients and clinicians.

Using Deep Learning to Automate Goldmann Applanation Tonometry Readings

PURPOSE

To develop an objective and automated method for measuring intraocular pressure using deep learning and fixed-force Goldmann applanation tonometry (GAT) techniques.

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Patients from an academic glaucoma practice.

METHODS

Intraocular pressure was estimated by analyzing videos recorded using a standard slit-lamp microscope and fixed-force GAT. Video frames were labeled to identify the outline of the reference tonometer and the applanation mires. A deep learning model was trained to localize and segment the tonometer and mires. Intraocular pressure values were calculated from the deep learning-predicted tonometer and mire diameters using the Imbert-Fick formula. A separate test set was collected prospectively in which standard and automated GAT measurements were collected in random order by 2 independent masked observers to assess the deep learning model as well as interobserver variability.

MAIN OUTCOME MEASURES

Intraocular pressure measurements between standard and automated methods were compared.

RESULTS

Two hundred sixty-three eyes of 135 patients were included in the training and validation videos. For the test set, 50 eyes from 25 participants were included. Each eye was measured by 2 observers, resulting in 100 videos. Within the test set, the mean difference between automated and standard GAT results was -0.9 mmHg (95% limits of agreement [LoA], -5.4 to 3.6 mmHg). Mean difference between the 2 observers using standard GAT was 0.09 mmHg (LoA,-3.8 to 4.0 mmHg). Mean difference between the 2 observers using automated GAT videos was -0.3 mmHg (LoA, -4.1 to 3.5 mmHg). The coefficients of repeatability for automated and standard GAT were 3.8 and 3.9 mmHg, respectively. The bias for even-numbered measurements was reduced when using automated GAT.

CONCLUSIONS

Preliminary measurements using deep learning to automate GAT demonstrate results comparable with those of standard GAT. Automated GAT has the potential to improve on our current GAT measurement standards significantly by reducing bias and improving repeatability. In addition, ocular pulse amplitudes could be observed using this technique.

Determining Significant Elevation of Intraocular Pressure Using Self-tonometry

SIGNIFICANCE

Icare HOME rebound tonometry is increasingly adopted into clinical practice for IOP phasing of glaucoma patients and suspects. Because of measurement differences with applanation tonometry and diurnal fluctuations, interpretation of the IOP measured with Icare HOME phasing can be challenging.

PURPOSE

The purpose of this study was to use a large patient cohort to develop a practical, analytical tool for interpreting Icare HOME measurements with respect to applanation pressure.

METHODS

IOP measurements using the Icare HOME and an applanation tonometer were taken prospectively in 498 consecutive patients. Bland-Altman, frequency distribution, and linear regression analysis were applied to determine measurement differences. A novel criterion, Threshold Icare HOME IOP, was developed to assist identification of elevation above target applanation pressure, considering the expected diurnal variation and measurement variability.

RESULTS

Icare HOME tended to underestimate applanation tonometry (mean bias, -1.7 mmHg; 95% limits of agreement, -7.0 to +3.6). Overall, differences were within ±3 mmHg in 71.5% and ±5 mmHg in 92% of patients. Based on the novel criterion developed, Icare HOME measurements that exceed target applanation pressure by 6 mmHg or greater are generally outside the 95% limit of expected observations.

CONCLUSIONS

The Threshold Icare HOME IOP is a novel and practical criterion that can assist clinicians in their interpretation of Icare HOME phasing measurements with respect to target applanation pressures. Elevation above the expected thresholds may prompt closer monitoring or even modifications to glaucoma management.