Comparative Evaluation of Rebound and Perkins Tonometers in Pediatric Glaucoma With Varied Corneal Characteristics

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.

Agreement of iCare IC200 tonometry with Perkins applanation tonometry in healthy children

PURPOSE

To assess interdevice agreement between the iCare IC200 rebound tonometer and Perkins applanation tonometry (gold standard) in a healthy pediatric population.

METHODS

A total of 42 eyes of 42 healthy children were assessed using both tonometers. Data was collected on subject's age, sex, best-corrected visual acuity, and central corneal thickness (CCT). Intraclass correlation coefficient (ICC) and Bland-Altman analyses were used to determine agreement between IC200 and Perkins applanation tonometers. Linear regression analyzed the effects of intraocular pressure (IOP) on device difference.

RESULTS

The mean age and standard deviation of healthy pediatric subjects was 10.0 ± 3.3 years. The mean difference between IC200 and Perkins tonometers (IC200-Perkins) was 0.72 mm Hg, with a mean of 17.1 ± 3.0 mm Hg and 16.4 ± 2.5 mm Hg, respectively. The absolute agreement, or ICC, between tonometers was 0.63 (95% CI, 0.56-0.70). Bland-Altman analysis showed 95% limits of agreement ranging from -5.2 to +6.6 mm Hg. CCT was not correlated with IOP for either the IC200 (P = 0.35) or the Perkins tonometer (P = 0.052).

CONCLUSIONS

Compared to applanation tonometry, IC200 overestimated IOP in healthy children, with a greater frequency of readings > +2 mm Hg than < -2 mm Hg compared to Perkins. There was moderate agreement between tonometers. CCT was not found to influence IOP measurement for either tonometer.

Rebound tonometry by iCare 200 (IC200): comparison with Tono-Pen in the operating room and Goldmann applanation in the clinic

BACKGROUND

Tonometry guides decision making in children with known or suspected glaucoma. The iCare IC200 is a recently FDA-approved rebound tonometer that can measure intraocular pressure (IOP) in both supine and upright patients. The purpose of this study was to evaluate this new tonometer against more commonly used standard instruments: Tono-Pen in the operating room (OR arm) and Goldmann applanation in the clinic (clinic arm).

METHODS

The OR arm included sequential children undergoing general anesthesia. The clinic arm included cooperative children seen in clinic. IOP was measured twice (right eye then left eye, repeat) with IC200 and either Tono-Pen (OR arm) or Goldmann (clinic arm).

RESULTS

A total of 99 children were included: 75 for the OR arm and 24 for the clinic arm. There was a strong correlation between the IOP measured by IC200 and each device (R² = 0.81 for Tono-Pen; R² = 0.78 for Goldmann). In the OR arm, the overall mean IOP difference (ΔIOP [Tono-Pen - IC200]) was -1.6 mm Hg. For eyes with corneal edema (n = 12), ΔIOP ranged from -8 to 15 mm Hg. At IOP >20 mm Hg, mean ΔIOP was -3.7 mm Hg. In the clinic arm, the mean ΔIOP (ΔIOP [Goldmann - IC200]) was -1.2 mm Hg.

CONCLUSIONS

In eyes of children under general anesthesia with IOP <20 mm Hg without corneal edema, IC200 and Tono-Pen correlated well. In cooperative clinic patients, Goldmann and IC200 correlated well over the range of IOP studied.