A comparison of Icare PRO and Perkins tonometers in anesthetized children

Validation of intraocular pressure measurement using tonometer AVIA across different postures: A Bland Altman analysis

AIMS/OBJECTIVES

Tonometry is a fundamental procedure in the diagnosis and management of glaucoma. Different tonometers have been proposed but none are as accurate as the Goldman applanation tonometry (GAT). Nonetheless, due to the limitations of GAT, mobile tonometry methods became prevalent. This study aims to examine the reliability of the Tono-Pen AVIA® (TPA) in measuring intraocular pressure (IOP) across different postures.

METHODS

A total of 196 eyes were prospectively examined for IOP changes using GAT and TPA. IOP measurements were taken across different postures using the TPA. Reliability of measurements was compared using interclass correlation coefficients (ICC), while agreement was represented using Bland-Altman analysis. Pearson r coefficient was used to measure correlations.

RESULTS

When compared to GAT (14.5 ± 4.4 mmHg), IOP readings were significantly higher for TPA at both seated (16.5 ± 4.5 mmHg; p < 0.001) and supine (16.9 ± 5.7; p < 0.001) positions. The ICC values for GAT and TPA among seated and supine patients were 0.79 (0.54-0.90) and 0.76 (0.48-0.87) indicating good reliability between the readings. There were significantly positive correlations between GAT and TPA at both seated (r = 0.626, p < 0.001) and supine (r = 0.727, p < 0.001) positions. Per Bland-Altman analysis, limits of agreement were -8.57 to 4.37 for GAT and seated TPA and -10.34 and 5.34 for GAT and supine TPA.

CONCLUSION

Good reliability exists between IOP measurements using GAT and TPA. However, the devices are not interchangeable and therefore cannot be used reciprocally in the same patient.

Comparison of the iCare rebound tonometer and the Perkins applanation tonometer in children under general anesthesia

INTRODUCTION

The goal of the study was to compare Perkins applanation tonometry and iCare rebound tonometry, evaluating their correlation and agreement in a diverse pediatric population under general anaesthesia (GA).

MATERIALS AND METHODS

Children undergoing an eye examination under GA between November 2019 and March 2020 were included. Intraocular pressure (IOP) was measured successively using the Perkins applanation tonometer and the iCare IC200 rebound tonometer. Ultrasonic central pachymetry and axial length were measured.

RESULTS

One hundred and thirty-eight eyes of 72 children were included. The mean age was 2.87years. IOP measurements obtained with the two tonometers were statistically and significantly highly correlated (r=0.8, P<0.001), although the iCare overestimated IOP by an average of 3.37mmHg (SD±4.48). The agreement between the two methods was moderate; the 95% agreement limits ranged from -5.41 to +12.15mmHg (r=0.5, P<0.001). The IOP difference between the two tonometers was weakly but significantly correlated with mean IOP (r=0.52; P=0.006). No correlation was found with axial length and pachymetry.

CONCLUSION

In this study, the IOP values obtained using the Perkins applanation tonometer and the iCare IC200 rebound tonometer were well correlated. The iCare tended to overestimate the IOP, especially for high IOP values. However, no underestimation of IOP was found with this device, hence its potential for glaucoma screening in children.

Pediatric Glaucoma-From Screening, Early Detection to Management

Pediatric glaucoma (PG) covers a rare and heterogeneous group of diseases with variable causes and presentations. Delayed diagnosis of PG could lead to blindness, bringing emotional and psychological burdens to patients' caregivers. Recent genetic studies identified novel causative genes, which may provide new insight into the etiology of PG. More effective screening strategies could be beneficial for timely diagnosis and treatment. New findings on clinical characteristics and the latest examination instruments have provided additional evidence for diagnosing PG. In addition to IOP-lowering therapy, managing concomitant amblyopia and other associated ocular pathologies is essential to achieve a better visual outcome. Surgical treatment is usually required although medication is often used before surgery. These include angle surgeries, filtering surgeries, minimally invasive glaucoma surgeries, cyclophotocoagulation, and deep sclerectomy. Several advanced surgical therapies have been developed to increase success rates and decrease postoperative complications. Here, we review the classification and diagnosis, etiology, screening, clinical characteristics, examinations, and management of PG.

24-h intraocular pressure patterns measured by Icare PRO rebound in habitual position of open-angle glaucoma eyes

PURPOSE

To measure the 24-h intraocular pressure (IOP) by Icare PRO rebound in healthy and primary open-angle glaucoma (POAG) eyes and compare it with non-contact tonometry (NCT).

METHODS

Thirty POAG patients, who were under IOP-lowering treatment, and 30 healthy subjects were included. Participants were hospitalized overnight for the 24-h IOP measurement. IOPs were measured by Icare PRO and NCT according to a standard protocol every 2 h during 24 h. The 24-h IOP curve and IOP-related parameters were compared between Icare PRO and NCT groups in POAG and healthy eyes.

RESULTS

The IOPs measured by Icare PRO in habitual position increased notably at 22:00 in the normal group and at 20:00 in the POAG group, reached peak at 0:00, stayed high until 4:00, and then decreased in both groups (all p < 0.05). The POAG patients had higher mean 24-h IOP, peak IOP, IOP fluctuation, and greater IOP change from supine to sitting position in the nocturnal period than those in the normal subjects even after adjusting for eyes, age, gender, CCT, and axial length (all p < 0.05).

CONCLUSIONS

The Icare PRO provides a well-tolerated approach for 24-h IOP monitoring in habitual position. Twenty-four-hour IOP in habitual position is more sensitive for detecting high nocturnal IOP peaks and greater IOP fluctuation for POAG patients.

Effect of general inhalational anesthesia on intraocular pressure measurements in normal and glaucomatous children

PURPOSE

To investigate the agreement between the intraocular pressure (IOP) measurements in the awake condition and under different stages of general inhalational anesthesia using sevoflurane in both glaucomatous and normal children.

METHODS

A prospective study was performed on 43 glaucomatous children and 30 age-matched controls. Baseline IOP of one eye was measured immediately before general anesthesia using Perkins tonometer and then re-measured under light, intermediate, and deep anesthesia, and then after intubation. Depth of anesthesia was determined using bispectral index pediatric sensor. The agreement between the IOP measurements before and during different stages of anesthesia was analyzed using Bland-Altman plots. Systematic and proportionate deviations between the IOP measurements were analyzed.

RESULTS

The mean age was 58.6 ± 41.99 months. The mean IOP was significantly lower at all stages of anesthesia in both groups. The coefficient of variation was over 20% in all measurements under anesthesia. For all IOP measurements during anesthesia, the limits of agreement were > 7 mmHg difference in the control group and > 20 mmHg in the glaucomatous group. The best agreement was with the IOP measurement after intubation (mean limit of agreement of -1.4 mmHg, 1.96 s range, -8.8-6 mm Hg) in the control group and with the IOP measurement under intermediate anesthesia (mean limit of agreement of -4.2 mmHg, 1.96 s range, -15.1-6.8 mm Hg) in the glaucomatous group.

CONCLUSIONS

Inhalational anesthesia has variable effects on IOP measurement at all stages of anesthesia. Caution should be taken when extrapolating the true IOP from these measurements.