Assessment of intraocular pressure measurement between Goldman applanation tonometer, rebound tonometer, non-contact tonometer, and its correlation with central corneal thickness

Purpose: To compare readings of intraocular pressure (IOP) taken with the Goldmann applanation tonometer (GAT), the non?contact tonometer (NCT), and the rebound tonometer (RBT), and to compare their correlation with central corneal thickness (CCT). Methods: This was a prospective, cross?sectional, observational study to which patients above 18 years of age were enrolled. A total of 400 eyes of 200 non?glaucomatous patients underwent IOP recordings using the GAT, NCT, and RBT, and CCT was also noted. Informed consent of the patients was taken. The IOP readings taken via the three methods were compared and correlated with CCT. Paired t test was used to compare the two devices. Simple and multivariate linear regression analyses were used to study the relationship between factors. A P value less than 0.05 was considered significant. Correlation was determined using the Pearson correlation coefficient, and a Bland–Altman graph was plotted. Results: Mean IOP measured by the NCT was 15.65 ± 2.80 mmHg, by the RBT was 14.23 ± 3.05 mmHg, and by the GAT was 14.69 ± 2.97 mmHg. The mean CCT was 510.61 ± 33.83 microns. The difference between mean IOP recorded by the NCT and that by the RBT was 1.41 ± 2.39 mmHg, between the NCT and GAT was 0.95 ± 2.03 mmHg, and between the GAT and RBT was 0.45 ± 2.22 mmHg. The difference between the IOP values was statistically significant (P < 0.005). All tonometers showed a statistically significant correlation with CCT, but it was observed that the NCT had a stronger correlation (0.4037). Conclusion: The IOP readings taken by all the three methods were comparable; however, RBT values were closer to GAT values. CCT did influence the IOP values, and this should be kept in mind while evaluating.

Accuracy of intraocular pressure measurements between non-contact tonometer and ICare rebound tonometer / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To analyze the accuracy of non-contact tonometer(NCT)and ICare rebound tonometer(RBT)in measuring intraocular pressure in glaucoma patients. <p>METHODS:A retrospective proportional control study. Totally 113 patients(185 eyes)with glaucoma were studied. Intraocular pressure was measured by RBT, NCT and Goldmann Applanation tonometer(GAT)at 9:00 and 16:00 and recorded as two sets of data, respectively. Their accuracy is evaluated by the rank sum test, and the international standard 8621 guide, Bland-Altman consistency analysis analyzed the consistency of the two groups of measurements, and the data were divided into two groups: abnormal intraocular pressure group(<10mmHg or >21mmHg)and normal intraocular pressure group(10-21mmHg). The consistency was analyzed between different groups. The spearman correlation analysis is adopted to analyze the correlation between ophthalmotonometers.<p>RESULTS: There were differences among the GAT, NCT and RBT measurements(<i>P</i><0.01). There was a strong correlation between the intraocular pressure measured value obtained by GAT and measured values obtained by RBT and NCT(<i>rs</i>=0.71, 0.77, <i>P</i><0.001). The measured values of NCT and GAT are close to each other without statistically significant differences(<i>P</i>=0.92). Compared with GAT, RBT has a higher intraocular pressure measured value, and there are significant differences(<i>P</i><0.05). However, compared with GAT, both NCT and RBT have a wide range of limits of agreement, and they are(-6.2-6.0mmHg)and(-5.2-7.6mmHg)respectively. In normal intraocular pressure groups, the ranges of limits of agreement are(-5.9-5.9mmHg)and(-4.3-7.5mmHg)respectively. In abnormal intraocular pressure groups, the ranges of limits of agreement are(-7.3-6.4mmHg)and(-7.5-5.6mmHg)respectively. The evaluation carried out in accordance with ISO 8612 guides indicates that the abnormal values more than the 95% of consistency restriction of NCT and RBT in the three groups are(3.9%, 11.3%, 12.2%)and(26.3%, 11.3%, 12.2%)respectively.<p>CONCLUSION: Both NCT and RBT cannot simply replace the GAT to measure the intraocular pressure of glaucoma patients. In glaucoma patients, with the deviation of the measured value from the normal intraocular pressure range, the measurement error of NCT and RBT also increase.

Rebound Tonometers versus Other Tonometers: Agreement among Readings and the Effects of Axial Length, Ocular Pulse Amplitude, and Central Corneal Thickness on Readings

OBJECTIVE: The aim of this study was to use intraocular pressure (IOP) measurements obtained via rebound tonometry (RBT, the I-care instrument), Goldmann applanation tonometry (GAT), non-contact tonometry (NCT), dynamic contour tonometry (DCT, PASCAL), and the TonoPen to investigate the consistency of readings among methods and the influence of ocular pulse amplitude (OPA), axial length (AL), and central corneal thickness (CCT) on RBT data. METHODS: We prospectively studied 123 eyes. IOP was measured via RBT, GAT, NCT, DCT, and the TonoPen. In addition, OPA was measured via DCT, AL, and CCT. Correlations among measurements using the various methods were evaluated, as were the effects of OPA, AL, and CCT on RBT data. RESULTS: RBT data were significantly correlated with data obtained via GAT, NCT, DCT, and the TonoPen; the highest correlation was with GAT. OPA was significantly correlated with IOP measured via GAT but not with IOP measured via RBT. Both AL and CCT were significantly correlated with IOP data obtained via RBT and GAT. CONCLUSION: Significant correlations were evident among IOP measurements obtained via RBT and other tonometry methods. However, the influence of AL and CCT on IOP measurements obtained via RBT requires careful consideration and interpretation. Although the IOP values obtained by GAT were correlated with OPA values obtained by DCT, this was not true of IOP data obtained by RBT. This might be associated with characteristic of RBT which has the relatively short corneal contact time.

Agreement of intraocular pressure measured by noncontact tonometer and Goldmann applanation tonometer : a Meta-analysis / 中华实验眼科杂志

Background Noncontact tonometer (NCT) is a common application in clinical ophthalmology,while its measured value is influenced by corneal parameter.In recent years,there existed some clinical trials discussing the agreement between NCT and gold standard Goldmann applanation tonometer (GAT),but there was still lack of evidence.Objective This study was to evaluate the agreement between NCT and GAT by applying evidence based medicine (EBM) method.Metbods A systematic literature retrieval was conducted from the MEDLINE,EMbase,CBM disc and CNKI database with the limitation of publishing time until June 2016.The literatures were screened according to the inclusion and exclusion criteria.The sample size,average age,sample characteristics and follow-up time were extracted.The value of intraocular pressure measured by NCT and GAT were analyzed.The overall effect size was analyzed using Review Manager 5.3 (from The Cochrane Collaboration) as weighted mean difference (WMD).There existed heterology in this study.Radom effect mode was used to evaluate and compare the difference between NCT and GAT value.Results Twenty four articles were retrieved.Six comparison studies incorporated with 478 eyes were included for Meta analysis.After random effects model was performed for correction.Intraocular pressure measured by NCT was 0.02 mmHg larger than that by GAT (1 mmHg =0.133 kPa).There was no significant difference in the measurement value of IOP between the two instruments (WMD =0.02,95％ CI:-0.59 to 0.63,P =0.95).Funnel chart method showed that literature publication bias existed in this study.Conclusions Normal persons' IOP obtained from NCT and GAT showed a good reproducibility.More comparison studies are needed to support this result.

Analysis of Postoperative Intraocular Pressure Underestimation Measured with Non Contact Tonometry after Corneal Refractive Surgery

PURPOSE: To analyze the postoperative intraocular pressure (IOP) underestimation measured with non-contact tonometry after corneal refractive surgery. METHODS: The postoperative IOP decrease measured with non-contact tonometry (NCT), regarded as IOP underestimation, was calculated in 253 LASIK patients and 281 LASEK patients. Multiple regression analysis was performed to determine the preoperative factors which affect postoperative IOP underestimation. The right eye results were reported in this paper. RESULTS: The postoperative IOP decrease was affected by age (r = -0.0420, p = 0.03), corneal ablation depth (r = 0.0466, p < 0.01), and operation method (LASIK or LASEK) (r = 0.6006, p < 0.01). For every 100 microm decrease of corneal thickness by LASIK, the IOP decreased 6.29 +/- 2.40 mm Hg in patients under 26 years of age and 6.12 +/- 2.53 mm Hg in patients above 26 years of age (p = 0.05). For every 100 microm decrease of corneal thickness by LASEK, the IOP decreased 5.77 +/- 2.37 mm Hg in patients under 26 years of age and 5.44 +/- 2.62 mm Hg in patients above 26 years of age (p = 0.05). CONCLUSIONS: The postoperative IOP underestimation measured with NCT was more prominent in younger-aged patients after LASIK than LASEK with deeper ablation depth.

Comparison of Rebound Tonometer, Non-Contact Tonometer, Goldmann Applanation Tonometer and the Relationship to Central Corneal Thickness

PURPOSE: To compare the level of accuracy of intraocular pressure (IOP) measurements of a rebound tonometer (RT) Icare(R), and non-contact tonometer (NCT), using Goldmann Applanation tonometer (GAT) as a reference to evaluate the influence of central corneal thickness (CCT) on IOP readings in the Korean population. METHODS: In a prospective study of 273 eyes, IOP was measured with RT, GAT, and NCT and compared to CCT measurements. Patients were assigned to one of 3 groups based on IOP measurements of GAT and 1 of 2 groups based on CCT. The comparison of the IOP values of RT, GAT, and NCT was performed between the IOP and CCT groups, and the differences among tonometers were evaluated. RESULTS: The RT showed statistically significant correlation with the GAT compared to the NCT. The CCT was related to RT measurements. The RT values compared to the GAT was underestimated in thin corneas and overestimated in thick corneas. CONCLUSIONS: There was a significant correlation between the RT and the GAT measurements compared with the NCT. However, RT is influenced by CCT and correlates less with GAT in low IOP ranges, suggesting that corneal thickness should be taken into consideration during such measurements.

Analysis in clinical efficiency of non-contact tonometer and indentation tonometer / 中国实用护理杂志

Objective To compare the measured IOP values by non-contact tonometer and indentation tonometer in order to evaluate the non-contact tonometer in clinical application. Methods 320 eyes of 160 patients for screening of IOP in the clinic were included in the observation, by self-control study, the IOP value of the non-contact tonometer(abbreviated NCT) and the indentation tonometer was compared. Results IOP values measured by NCT was lower than that mesgured by indentation tonometer. Conclusions IOP values measured by NCT was lower than that measured by indentation tonometer, for IOP value around 2.67 kPa measured by NCT, it is best to use indentation tonometer to retest or coming again for subsequent visit.

Factors Affecting the Ocular Response Analyzer Parameters in Normal Korean

PURPOSE: To identify the normal range of factors which can be measured with Ocular Response Analyzer (ORA, Reichert Inc., Depew, NY, USA) in normal Korean, and to analyze factors affecting ORA by measuring intraocular pressure (IOP) of noncontact tonometer (NCT) and central corneal thickness (CCT). METHODS: Three hundred and one normal Korean subjects who did not have specific ophthalmological diseases and surgeries in the past were recruited for this study. Corneal hysteresis (CH), corneal response factor (CRF), corneal-compensated IOP (IOPcc), and Goldmann correlated IOP (IOPg) were measured using ORA. In addition, IOP of NCT and CCT were measured and the results and factors analyzed. RESULTS: The mean CH measured among normal Korean subjects in this study was 10.70 mmHg. The mean CRF was 10.40 mmHg. CH and CRF were significantly higher in the juvenile group. IOPcc and IOPg as measures of IOP using the ORA had significant correlation with IOP of NCT. In particular, IOPcc appeared to be independent of CCT. CONCLUSIONS: CH and CRF were different according to age, indicating a difference in biomechanical properties of the cornea. In particular, IOPcc is more important as it is independent of corneal thickness and should be compensated in general measurements of IOP reflecting biomechanical properties.

Comparison of the intraocular pressure value measured with Goldmann applanation tonometer and non-contact tonometer / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To assess the relative agreement of GAT and NCT in IOP measurement by comparing the differences between Goldmann applanation tonometer (GAT) and non-contact tonometer (NCT) in intraocular pressure (IOP) detection.METHODS: IOP of 529 eyes of 265 volunteers were measured with both NCT and GAT, respectively.RESULTS: The measurement results of NCT were lower than that of GAT, there was significant difference between the IOP measured with NCT and GAT (19.13 vs23.43, t=22.644, P＜0.05). With the increasing of IOP values, the difference magnitude was greater, especially in IOP group that was more than 30mmHg, but the correlation coefficient became lower.CONCLUSION: The measurement results with NCT are lower than that of GAT. When the IOP with the NCT is in borderline value, it need be corrected with GAT, in order to discover the pathologically elevated IOP and avoid the misdiagnosis and mistreatment of glaucoma.

Comparative Effect of Timolol, Levobunolol and Betaxolol on IOP in Patients of Chronic Simple Glaucoma

In this prospective randomized parallel study we compared the effects of topical timolol maleate, levobunolol hydrochloride and betaxolol hydrochloride on intraocular pressure (IOP) in the patients of primary open angle glaucoma after 16 weeks of instillation as 1 drop 12 hourly in 0.5% concentration. 23 eyes of 16, 19 eyes of 12 and 20 eyes of 12 patients were included in timolol, levobunolol and betaxolol groups respectively. Timolol, levobunolol and betaxolol lowered IOP by 13.05 ± 1.53, 14.05 ±1.47 and 7.58 ± 0.90mmof Hg respectively after 6weeks and by16.12±1.67,16.28 ±1.85 and 8.535 ± 0.983 mm of Hg respectively after 16 weeks (P<0.001). Both levobunolol and timolol produced greater reduction in IOP than betaxolol (P<0.001). The results of our study indicated that betaxolol is less efficacious in lowering IOP in Indian patients and could only be preferred over timolol in glaucoma patients with associated chronic obstructed pulmonary disease (COPD) or bronchial asthma. However, Levobunolol could be a better alternative to timolol , as being a longer acting agent with IOP control for 24 hrs after single instillation and can be used as once a day instillation with better safety profile.

The Influence of Central Corneal Thickness on Intraocular Pressures Measured with Goldmann Applanation Tonometer and Non-contact Tonometer

It is well documented that increased corneal thickness leads to artificially high estimations of intraocular pressure(IOP) measured with applanation tonometer. To evaluate the influence of central corneal thickness on IOPs measured with non-contact tonometer and Goldmann applanation tonometer and on the IOP discrepancies between two tonometer according to corneal thickness, the IOPs and central corneal thickness of 96 eyes of 48 persons who visited to have their high IOPs evaluated were measured with Goldmann applanation tonometer, non-contact tonometr(CT-50, Topcon, Japan), and corneal pachometer(Humphrey ultrasonic pachometer-850). IOPs measured with each tonometer showed statistically significant linear correlation(p0.1). In conclusion, the central corneal thickness must be considered in estimating IOP and the IOP differences measured with Goldmann applanation tonometer and non-contact tonometer were not statistifically significantly increased as the corneal thickness increased.

Comparison of the Noncontact Tonometer with Goldmann Tonometer

Several kinds of non-contact tonometers have been used since the first non-contact tonometer was introduced in the 1970's in order to measure intraocular pressure with easiness and accuracy. However several problems were still remained because of:he inaccuracy of the non-contact tonometer in high and low range of intraocular pressure. A new non-contact tonometer (Model CT-20, Japan) was recently introduced by Topcon Company to evaluate the clinical efficacy of the non-ccntact tonometers. The authors measured the intraocular pressure with Topcon tonometer, AO tonometer and Pulsair non-contat tonometer and compared the results with those measured with Goldmann tonometer. The results were as follows: 1) The correlation coefficient between Goldmann and Topcon tonometer was 0.8452 (p=0.001), Goldmann and Pulsair tonometer was 0.7084 (p=O.OOl) and Goldmann and AO tonometer was 0.6048 (p=O.OOl) in the normal eyes. 2) The correlation coefficient between Goldmann and Topcon tonometer was 0.8651 (p=0.0001) in the ocular hypertensive or open angle glaucoma eyes. 3) The correlation coefficient between Goldmann and Topcon tonometer was 0.6987 (p=0.000l) in the low lOP eyes. 4) The correlation coefficient between Goldmann and Topcon tonometer was 0.6829 (p=0.0001) in the high myopic eyes. As above, a new-contact tonometer (Model CT-20, Japan) made by Topcon Company was relatively accurate in measuring not only the intraocular pressure of normal eyes but that of ocular hypertensive, low IOP and high myopic eyes.

Non-contact tonometry: an ideal method for mass screening

We evaluated one of the new non-contact tonometers, the Pulsair non-contact tonometer, to assess its accuracy and reliability. Measurements on 101 eyes were used to assess its accuracy against Goldmann tonometry measurements, and another 24 eyes were used to assess its reliability (reproducibility). The results showed the instrument to be highly accurate and reliable in measurement.