IOP agreement between I-Care TA01 rebound tonometer and the Goldmann applanation tonometer in eyes with and without glaucoma

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 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.

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

PRECIS

Icare tonometer overestimated intraocular pressure (IOP) as compared with Perkins and this variation was higher in IOP>19 mm Hg and corneal opacity in patients with pediatric glaucoma.

PURPOSE

To compare the IOP measured by Icare ic200 with Perkins tonometer in pediatric glaucoma with different corneal characteristics.

METHODS

Patients of pediatric glaucoma posted for routine examination under anesthesia, age below 12 years were enrolled. All patients underwent IOP measurement with Perkins and Icare ic200 tonometer by the same observer. Basic demographic data and other relevant clinical data were recorded. Central corneal thickness (CCT), horizontal corneal diameter, and corneal characteristics such as cornea clarity was recorded.

RESULTS

A total of 194 eyes of 105 patients were analyzed. The difference between Perkins and Icare IOP was -0.816 mm Hg with the Bland-Altman plot 95% limits of agreement (LoA) from -11.194 to 9.562 mm Hg and 5.1% (10) values lying outside LoA. At IOP <19 mm Hg, the difference was -0.65 mm Hg and IOP ≥19 mm Hg, the difference was higher, -1.12 mm Hg. In the clear cornea group (123 eyes), the difference in IOP by 2 tonometers was -0.776 mm Hg with the Bland-Altman plot 95% LoA between -10.679 and 9.128 mm Hg. In hazy corneas (36 eyes), the difference in IOP was 0.531 mm Hg. The Bland-Altman plot showed 95% LoA between -6.242 and 7.303 mm Hg. In the scarred cornea group (35 eyes), the difference in IOP between the 2 was -2.343 mm Hg and the Bland-Altman plot showed wide 95% LoA from -16.302 to 11.616 mm Hg.

CONCLUSION

Icare tonometer overestimated IOP as compared with Perkins and this variation was higher in eyes with IOP≥19 mm Hg, CCT >615 μm, and scarred corneas. A moderate correlation between IOP and CCT for both tonometers was noted.

Tonometers-which one should I use?

Although several factors are known to play a role in the development and progression of glaucoma, intraocular pressure (IOP) remains the only modifiable risk factor. Medical and surgical treatments for glaucoma both aim to reduce IOP to minimize disease progression. Tonometry is therefore an essential element of the ophthalmological exam. There are several types of tonometers available currently. These range from well-established instruments that have been in clinical use for decades to new devices, which are the result of recent technological advances. The various instruments have advantages and disadvantages that affect their suitability for a given setting, purpose, and patient population. In this review, we aim to describe the most commonly available tonometers today along with their advantages, disadvantages, and applicability.

Comparison of the iCare rebound tonometer and the Goldmann applanation tonometer

Tonometry is a fundamental procedure in routine ophthalmologic examination. Although regarded as the reference standard, the Goldmann applanation tonometer (GAT) has its limitations. A new portable alternative to the GAT is the iCare rebound tonometer (RT). The aim of the present study was to compare the intraocular pressure (IOP) results obtained using the RT and GAT and then correlate the results with the central corneal thickness (CCT). Moreover, the tolerability and safety of the RT were evaluated. The IOP of 336 patients (672 eyes) was determined by the RT and GAT. The patients were divided into three groups (group A, 7-15 mmHg, n=74; group B, 16-22 mmHg, n=218; and group C, 23-50 mmHg, n=44), based on the GAT IOP readings. Pachymetry and slit lamp inspection were also performed. To establish an agreement between the devices, a Bland-Altman analysis and paired t-test were performed. The correlation between CCT and IOP readings obtained by the two devices were assessed using linear regression correlation analysis. The mean IOP values of the RT and the GAT were 18.30±5.10 and 18.52±4.46 mmHg, respectively. There were no significant differences between them (t=-1.31, P=0.19). The 95% confidence interval of the differences between the two devices was -5.80-6.24 mmHg. The RT readings are correlated well with those of GAT (r=0.806, P=0.001). However, the RT measurements were significantly (t=-2.84, P=0.007) lower (-1.66±3.87 mmHg) than those obtained with GAT when GAT ≥23 mmHg. Both the RT (r=0.390, P=0.001) and the GAT (r=0.191, P=0.001) showed positive correlations with CCT. The IOP measurement with RT was well tolerated. None of the corneal epithelial defects was detected and all subjects denied discomfort. The RT is well tolerated and safe, and can be considered a reliable alternative to GAT for patients in a low to moderate IOP range. However, in patients with high IOP values, the measurements obtained with RT did not correlate well with those obtained by GAT. The RT readings are influenced more by CCT compared to GAT.