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Purpose We sought to compare the intraocular pressure ( IOP) measured by RKT-7700 and CT-80 noncontact tonometers ( NCTs) with that measured by Goldmann applanation tonometry ( GAT). We also examined the influence of central corneal thickness ( CCT) on the agreement between both NCTs and GAT in a sub-population of healthy, young normals. Methods Triplicate IOP and CCT measurements were obtained twice from one randomized eye of 49 subjects (28 males and 21 females) aged 22.2 ± 1.3 (mean ± S.D.) years. Goldmann tonometry was performed subsequent to assessment with the RKT-7700 and CT-80, to negate the 'ocular massage effect', followed by ultrasound pachymetry. The results from each method were compared and assessed for repeatability and between-observer reproducibility. Analysis was performed to determine the correlation between the differences in IOP measurements and corneal thicknesses. Results The mean differences (±S.D.) in sessions 1 and 2 respectively between RKT-7700 and GAT (2.6 ± 2.0 and 2.7 ± 1.4 mmHg), between CT-80 and GAT (2.8 ± 2.0 and 3.2 ± 1.3 mmHg) were statistically significant ( p < 0.0001). The repeatability coefficients in sessions 1 and 2 respectively were; ±1.2 and ±1.0 mmHg ( GAT), ±1.3 and ±1.6 mmHg ( CT-80), ±2.3 and ±1.7 mmHg ( RKT-7700) and inter-observer reproducibility was; ±1.9 ( RKT-7700), ±2.3 ( GAT) and ±2.6 mmHg ( CT-80). Between the corneal thickness and the differences in GAT-measured and NCT-measured IOPs, there was a significant negative correlation and a trend for a larger difference in thicker corneas. Conclusion Neither the RKT-7700 nor the CT-80 can be used interchangeably with the Goldmann tonometer, although all three tonometers give repeatable measurements of IOP, in this sub-population. IOP differences between GAT and the NCTs significantly correlated with CCT, with the possibility of even greater differences in thicker corneas. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To quantify the influence of soft contact lens power and thickness on the intraocular pressure (IOP). Methods: Thirty-nine young, healthy adult volunteers completed this study. One eye of each subject was randomly assigned either a +6D or a −6D high water content daily disposable lens. The other eye was fitted with the second lens. Triplicate measurements of IOP were taken before, during, and after contact lens wear. Each time, IOP was assessed in a randomized order with two noncontact tonometers. The lenses were swapped between eyes during a second session of measurements, one week later. Results: In the first session with the +6D lenses, the average IOPs (±SDs) before, with the lenses fitted, and after the lenses were removed, were: 14.3±2.9mmHg, 17.0±3.3mmHg and 13.9±3.1mmHg, respectively, for the CT80 and 13.6±3.1mmHg, 17.1±4.5mmHg and 13.3±2.9mmHg, respectively, for the PT100. The corresponding values for the first session with the −6D lenses were: 14.3±3.1mmHg, 13.1±3.1mmHg and 14.1±3.3mmHg, respectively, for the CT80 and 13.6±3.2mmHg, 13.0±3.0mmHg and 13.6±3.2mmHg, respectively, for the PT100. IOP significantly (P <0.05) increased (+ΔIOP=2.7±0.4mmHg with the CT80 in the first session) with the +6D lenses, but decreased (P <0.05) when the −6D lenses were fitted (−ΔIOP=0.6±0.2mmHg with the PT100 in the first session). The soft contact lens-induced changes were consistent between sessions but varied between tonometers. Conclusions: The measurement of IOP through soft contact lenses resulted in consistent, statistically significant differences in IOP, which were not uniform across tonometers and which did not appear to be solely related to the central thickness of the soft contact lenses. [Copyright &y& Elsevier]

Background: Several authors believe it is necessary to randomise the order in which contact and non-contact tonometers are used in comparison studies. This study was carried out to investigate the effect of repeated applanation on the measured intraocular pressure. Methods: One set of measurements per session was made on each of three sessions (one session per day) with the Goldmann and two non-contact tonometers (Topcon CT80 and Keeler Pulsair EasyEye), in a pre-determined order, on one randomly selected eye of 120 subjects randomised to one of two groups. For session one, only the non-contact tonometers were used to assess the intraocular pressure of both groups. For session two, either non-contact or Goldmann tonometry was performed first and this order was reversed for session 3. Average intraocular pressures were compared between sessions to determine the presence or absence of effects on the intraocular pressure caused by prior repeated applanation with the Goldmann or either one (or both) of the non-contact tonometers. Results: Prior applanation with a non-contact tonometer did not cause a significant (p > 0.05) reduction of the mean pressure measured with either non-contact tonometer. The mean pressure was slightly but significantly (p < 0.05) reduced (for both non-contact tonometers in both subject groups) when non-contact tonometry was performed after Goldmann tonometry. There was no significant difference (p > 0.05) between the pressures measured with the Goldmann tonometer prior to and subsequent to non-contact tonometry, in both subject groups. Conclusion: A small but statistically significant reduction in the intraocular pressure was found following applanation with the Goldmann tonometer but not with either one of two non-contact tonometers. [ABSTRACT FROM AUTHOR]

Background: In studies aimed at assessing the accuracy and repeatability of non-contact tonometers, the order in which these tonometers and the Goldmann tonometer are used is usually randomised despite studies in the literature that demonstrate an ocular massage effect that occurs post-applanation but not after non-contact tonometry. The purpose of this study was to investigate the effect of repeated corneal applanation on subsequent assessments of IOP. Methods: Data were obtained from 65 left eyes of 65 young, oculovisual normals. Three sets of IOP measurements were obtained, one set with the Goldmann applanation tonometer and two with the Topcon CT80 non-contact tonometer (one set each before and after applanation with the Goldmann tonometer), in each one of two separate measurement sessions, one week apart. Results: The average (and SD) IOP measured with the Goldmann tonometer in the first session (14.8 ± 2.9 mmHg) did not vary significantly from the IOP measured with the non-contact tonometer (pre-applanation) in both sessions or with the average Goldmann IOP in the second session. The bias (mean difference ± SD) between methods was 0.3 ± 1.4 mmHg and 0.4 ± 1.4 mmHg, respectively, for the first and second sessions, with the CT80 (pre-applanation) recording the higher IOP in both sessions. The within-session repeatability coefficients were ±2.3 mmHg, ±2.6 mmHg, ±2.1 mmHg and ±2.0 mmHg for the CT80 (pre-applanation) in the first and second sessions, and the Goldmann tonometer in the first and second sessions, respectively. Test-retest repeatability coefficients were ±2.8 mmHg and ±2.5 mmHg for the CT80 (pre-applanation) and the Goldmann tonometer respectively. Post-applanation with the Goldmann tonometer, there was a statistically significant (p < 0.05) reduction (1.5 ± 1.2 mmHg in session 1) in the IOP measured with the non-contact tonometer in both sessions. Conclusion: These results suggest that repeated corneal applanation leads to a statistically significant reduction in IOP on subsequent measurements. [ABSTRACT FROM AUTHOR]

Background: The reliability of non-contact tonometers has been reported extensively in the literature. This study was designed to assess reliability of the new Topcon CT80 non-contact tonometer in normotensive subjects, using the Goldmann tonometer as the standard. Methods: The accuracy of the Topcon CT 80 non-contact tonometer was assessed by comparing its IOP assessments with those of the Goldmann applanation tonometer, on 60 right eyes of young healthy subjects with normal intraocular pressures. Each subject’s intraocular pressure was assessed with each technique on two separate occasions, one week apart. The reliability of each technique was determined by the assessment of its inter-session repeatability using the Bland-Altman method. The 95 per cent limits of agreement for the two methods were also determined. Results: No statistically significant difference was found between the average intraocular pressures measured with the two techniques (p > 0.05). The inter-session repeatability indices for the two techniques did not differ significantly (p > 0.05). The mean difference in intraocular measurements between the two techniques was 0.2 ± 1.5 mmHg (mean ± SD) and the 95 per cent limits of agreement were -3.14 and +2.74 mmHg, with the non-contact tonometer returning higher readings than the Goldmann tonometer. Conclusion: In this sample of normotensive subjects, the Topcon CT80 non-contact tonometer proved to be accurate and as reliable as the Goldmann tonometer in the assessment of intraocular pressure. Thus, it can be used as an objective clinical method for the assessment of normal intraocular pressure. [ABSTRACT FROM AUTHOR]