三种眼压计测量高眼压儿童眼压及其与中央角膜厚度的关系

目的：探讨经Topcon眼压计(non-contact tonometry,NCT)初筛高眼压的屈光不正儿童的中央角膜厚度(central corneal thickness,CCT)分布,以及NCT、Goldmann压平眼压计(Goldmann applanation tonometry,GAT)与OCULUS Corvis ST角膜生物力学分析仪(CST)所测眼压值的差异,并分析眼压和CCT的相关性。

方法：选择经NCT测量单眼或双眼眼压高于21mmHg的非青光眼屈光不正儿童39例78眼,用CST和GAT再次进行眼压测量,两种仪器的测量顺序随机,同时用CST测量CCT并根据CCT进行眼压校正。根据CCT分成正常组和较厚组,分析经NCT初筛高眼压的屈光不正儿童的总体CCT分布情况,探讨三种仪器所测眼压值的不同及其与CCT的相关性。

结果：正常CCT组,CST低于GAT和NCT的眼压测量值,差异有统计学意义(F=5.12,P=0.01); 较厚组,三种眼压测量方式的眼压测量值比较,差异均有统计学意义(F=15.72,P<0.001)。NCT和GAT眼压值与CCT呈明显正相关(r_NCT=0.298,P_NCT=0.04; r_GAT=0.408,P_GAT= 0.01); CST校正眼压值与CCT无明显相关性(r_CST=0.062,P_CST=0.593)。

结论：NCT初筛高眼压的屈光不正儿童的CCT偏厚,CST校正眼压低于NCT和Goldmann眼压,NCT和GAT所测眼压与CCT呈正相关; 对于CCT偏厚的儿童患者,CST校正眼压比NCT和GAT更接近于真实眼压值。     

Comparison of dynamic contour tonometry with Goldmann applanation tonometry in glaucoma practice

Purpose: To compare intraocular pressure (IOP) readings taken using dynamic contour tonometry (DCT) with IOP readings taken with Goldmann applanation tonometry (GAT) in eyes with glaucoma or ocular hypertension. Methods: The present study included 100 eyes in 100 patients with glaucoma or ocular hypertension. After pachymetry DCT and GAT were performed. Intraocular pressures as measured with DCT and GAT were compared with one another and with central corneal thickness (CCT). Results: Mean DCT IOP measurements (20.1 ± 4.3 mmHg) were significantly (p < 0.001) higher than GAT IOP values (17.9 ± 4.7 mmHg). The mean difference between DCT and GAT measurements was 2.1 mmHg (range ? 3.4 to 9.7 mmHg). The difference followed a normal distribution. Measurements made with DCT and GAT correlated significantly with one another (Spearman’s rho = 0.761, p < 0.001). Neither GAT nor DCT measurements showed a significant correlation with CCT (537 ± 39 μm, range 458–656 μm). Multivariate regression analysis has shown that the difference between DCT and GAT is influenced significantly by ocular pulse amplitude (r = ? 0.334, p = 0.001) and it is not influenced by CCT (r = ? 0.106, p = 0.292). Conclusions: In eyes with glaucoma or ocular hypertension, DCT facilitates suitable and reliable IOP measurements which are in good concordance with GAT readings. Variation in CCT cannot by itself explain the differences in measurements taken with DCT and GAT in a number of eyes.     

Dynamic contour tonometry versus Goldmann applanation tonometry: a comparative study

Background Various sources of error, including central corneal thickness (CCT) and structural corneal rigidity, have been proposed for Goldmann applanation tonometry (GAT). The Pascal dynamic contour tonometer (DCT) is a novel device designed for intraocular pressure (IOP) measurements assumed to be largely independent of CCT and corneal curvature. We compared DCT with GAT in eyes with normal corneas of various thickness.Methods We prospectively measured IOP using DCT and GAT in random order in 100 eyes of 100 subjects (M:F=46:54; mean age 42±19, range 23–88 years).Results Mean DCT values were about 1mmHg higher than GAT readings (16±3 vs 15±3 mmHg, p=0.001). Bland–Altman analysis of individual pairs of DCT and GAT measurements revealed a bias of –1.0 mmHg [95% confidence interval (CI): ±1.2]. Neither GAT nor DCT showed a significant correlation with CCT (533±48, range 399–641 m).Conclusions In eyes with normal corneas, DCT allows suitable and reliable IOP measurements which are in good concordance with GAT. Comparison of DCT with intracameral manometry is desirable in the future.     

A comparison of the Goldmann applanation and non-contact (Keeler Pulsair EasyEye) tonometers and the effect of central corneal thickness in indigenous African eyes

The Keeler Pulsair EasyEye non‐contact tonometer (NCT) was introduced into practice at Rachel Eye Center Abuja, Nigeria, where the patients are indigenous Africans. This was compared to the ‘gold standard’ Goldmann applanation tonometer (GAT) to determine if the instrument was accurate in Africans, with particular reference to the influence of central corneal thickness (CCT). Patients and methods:  174 eyes of 88 patients were analysed. Pachymetry was performed using Sonomed PacScan AP300, and GAT with the Haag Streit R‐900. Pachymetric corrections of NCT (NCTc) and GAT (GATc) were carried out with the Sonomed algorithm. Pearson’s correlation r, linear regression analysis, Student t‐test and Bland–Altman analysis were used to compare the instruments. Results:  Mean NCT readings were similar (17.36 mmHg) to mean GAT (17.42 mmHg; p = 0.769). GAT/NCT correlation coefficient, r, was 0.883 as compared with 0.868 for GATc/NCTc. The linear regression equation was GAT = 2.79 + 0.84*NCT (r² = 0.78). Forty‐five per cent of differences were within 1 mmHg, while 79% were within 3 mmHg. This was similar to findings in some studies on Caucasians. Bland–Altman analysis however suggested that the spread of differences was wider than in those studies. Outliers (differences more than 5 mmHg) sometimes reflected difficulties encountered with GAT in routine practice. Mean CCT was 537.9 μm, (S.D. 38.4, 95% confidence interval 532.1–543.7 μm) and CCT appeared lower than in Caucasians. Both GAT and NCT IOP tended to rise with increasing CCT but NCT had a greater tendency to do so. Regression analysis suggested that NCT IOP increased by 0.6 mmHg for every 10 μm increase in CCT, compared to 0.4 mmHg for GAT. Thirty‐eight per cent of the patients preferred NCT as opposed to 25% GAT. Conclusions:  The Keeler Pulsair EasyEye gives reliable measurements of IOP in African eyes but is significantly affected by CCT. Particularly in borderline cases where management decisions have to be taken, it may be necessary to have pachymetric corrections based on an NCT algorithm, which appears steeper than the GAT algorithm.     

Effect of corneal thickness on intraocular pressure measurements with the Pascal dynamic contour,Canon TX‐10 non‐contact and Goldmann applanation tonometers in healthy subjects

Purpose: To investigate the effects of central corneal thickness (CCT) on intraocular pressure (IOP) measurements of the Pascal dynamic contour tonometry (DCT), Canon TX‐10 non‐contact tonometry (NCT) and Goldmann applanation tonometry measurements (GAT) in healthy subjects. Methods: IOP values of 135 eyes with normal corneas of 135 healthy volunteers were determined by DCT, NCT and by GAT. The CCT was measured using an ultrasonic pachymeter after all IOP determinations had been made. Results: When DCT measurements were compared (IOP = 17.52 ± 2.0 mmHg) with NCT measurements (IOP = 16.54 ± 2.77 mmHg) and GAT measurements (IOP = 15.07 ± 2.35 mmHg), DCT measurements were significantly higher than NCT and GAT (p < 0.001). There was a significant correlation between CCT with both NCT (r = 0.260, p = 0.003) and GAT measurements (r = 0.257, p = 0.005). There was a weak correlation that was not statistically significant between CCT and DCT (r = 0.160, p = 0.079). Conclusion: The IOP measurements with DCT seem to be less dependent on CCT. NCT appears to be more affected by variation in CCT than GAT.     

Assessment of intraocular pressure measured by Reichert Ocular Response Analyzer, Goldmann Applanation Tonometry, and Dynamic Contour Tonometry in healthy individuals

AIM: To investigate the accuracy of intraocular pressure (IOP) as measured by a Reichert Ocular Response Analyzer (ORA), as well as the relationship between central corneal thickness (CCT) and IOP as measured by ORA, Goldmann applanation tonometry (GAT), and dynamic contour tonometry (DCT). METHODS: A total of 158 healthy individuals (296 eyes) were chosen randomly for measurement of IOP. After CCT was measured using A-ultrasound (A-US), IOP was measured by ORA, GAT, and DCT devices in a randomized order. The IOP values acquired using each of the three tonometries were compared, and the relationship between CCT and IOP values were analyzed separately. Two IOP values, Goldmann-correlated IOP value (IOPg) and corneal-compensated intraocular pressure (IOPcc), were got using ORA. Three groups were defined according to CCT: 1) thin cornea (CCT<520μm); 2) normal-thickness cornea (CCT: 520–580μm); and 3) thick cornea (CCT>580μm) groups. RESULTS: In normal subjects, IOP measurements were 14.95±2.99mmHg with ORA (IOPg), 15.21±2.77mmHg with ORA (IOPcc), 15.22±2.77mmHg with GAT, and 15.49±2.56mmHg with DCT. Mean differences were 0.01±2.29mmHg between IOPcc and GAT (P>0.05) and 0.28±2.20mmHg between IOPcc and DCT (P>0.05). There was a greater correlation between IOPcc and DCT (r=0.946, P=0.000) than that between IOPcc and GAT (r=0.845, P=0.000). DCT had a significant correlation with GAT (r=0.854, P=0.000). GAT was moderately correlated with CCT (r=0.296, P<0.001), while IOPcc showed a weak but significant correlation with CCT (r=?0.155, P=0.007). There was a strong negative correlation between CCT and the difference between IOPcc and GAT(r=-0.803,P=0.000), with every 10μm increase in CCT resulting in an increase in this difference of 0.35mmHg. The thick cornea group (CCT>580μm) showed the least significant correlation between IOPcc and GAT (r=0.859, P=0.000); while the thin cornea group (CCT＜520μm) had the most significant correlation between IOPcc and GAT (r=0.926, P=0.000). The correlated differences between IOPcc and DCT were not significant in any of the three groups (P>0.05). CONCLUSION: Measurement of IOP by ORA has high repeatability and is largely consistent with GAT measurements. Moreover, the ORA measurements are affected only to a small extent by CCT, and are likely to be much closer to the real IOP value than GAT.     

Physiological diurnal variability and characteristics of the ocular pulse amplitude (OPA) with the dynamic contour tonometer (DCT-Pascal<Superscript>®</Superscript>)

PURPOSE: The Pascal dynamic contour tonometer (DCT) allows measurement of intraocular pressure (IOP) independently of corneal properties. It records, simultaneously, haemodynamic IOP fluctuations and the difference between the systolic and the diastolic IOP corresponding to the ocular pulse amplitude (OPA). The OPA indirectly reflects choroidal perfusion and could be considered as an independent risk factor in glaucoma. We aimed to establish the physiological diurnal variability of the OPA and its correlations with other biophysical parameters because its characteristics remain partly unclear. METHOD: Prospective study including 52 eyes of 28 normal subjects with Goldmann applanation tonometry (GAT) IOPs < 22 mmHg. Subjects treated with systemic medications that could interfere with blood pressure or heart rate were excluded. IOP was measured at 9:00 am, 1:00 pm, and 4:00 pm by GAT and DCT. Two consecutive GAT followed by three consecutive DCT measurements were performed in each session by the same clinician (SP). Only DCT measurements with quality 1 and 2 were taken into account. Blood pressure, pulse rate, and central corneal thickness (CCT) were recorded after the last IOP measurements. Spearman correlation coefficient was used for assessment of correlations. RESULTS: Mean age was 40 +/- 14 years. Mean DCT values were significantly higher than GAT readings (mean = 16.8 +/- 2.0 vs. 15.2 +/- 2.8 mmHg, P < 0.02). The mean OPA was 2.2 +/- 0.7 mmHg (range: 1-3.4 mmHg). The mean amplitude of diurnal OPA fluctuations was 0.4 mmHg. There was no significant difference in the mean OPA values at each time of the diurnal curve. The intraclass correlation (ICC) of only one OPA measurement in relation to part of total variance due to inter-measurement variation was 78%. Averaging over three independent readings of OPA improved ICC to 91%. The OPA was correlated with GAT (r = 0.31, P < 0.0001) and DCT IOP measurements (r = 0.49, P < 0.0001). It was correlated neither with blood pressure nor with age. OPA values of both eyes of the same individual were highly correlated (r = 0.89, P < 0.0001). CONCLUSION: In normal healthy eyes, the ocular pulse amplitude remains stable during normal outpatient office hours and was not correlated with blood pressure or age of patients.     

Comparisons between Pascal dynamic contour tonometry, the TonoPen, and Goldmann applanation tonometry in patients with glaucoma

PURPOSE: To compare intraocular pressure (IOP) measurements taken with Pascal dynamic contour tonometry (DCT), the TonoPen and the Goldmann applanation tonometry (GAT). The influence of central corneal thickness (CCT) on IOP measurements taken with Pascal DCT and the TonoPen was evaluated. METHODS: One eye in each of 101 consecutive patients with primary open-angle glaucoma (POAG) underwent ultrasonic CCT measurement and IOP evaluation with GAT, Pascal DCT and the TonoPen in random order. The agreement between results from Pascal DCT and the TonoPen and those of GAT was assessed using the Bland-Altman method. The deviation of Pascal DCT and TonoPen readings from GAT values, corrected for CCT, was calculated and correlated to CCT using a linear regression model. RESULTS: The mean of the differences in IOP measurements was 3.2 +/- 2.4 mmHg for Pascal DCT minus GAT readings and 0.5 +/- 4.5 mmHg for TonoPen minus GAT readings. The 95% confidence interval of differences in IOP measurements was higher between TonoPen and GAT readings (- 6 to 7 mmHg) than between Pascal and GAT readings (0.1-6.8 mmHg). Pascal DCT significantly overestimated IOP compared with GAT, especially for higher IOP readings. Bland-Altman scatterplots showed reasonable inter-method agreement between Pascal DCT and GAT measurements, and poor agreement between TonoPen and GAT measurements. The deviations of Pascal DCT and TonoPen readings from the corrected GAT values were both highly correlated with CCT values (linear regression analysis, p < 0.0001). The mean change in measured IOP for a 10-microm increase in CCT was 0.48 mmHg for Pascal DCT and 0.74 mmHg for the TonoPen. CONCLUSIONS: Agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT. Measurements of IOP obtained with both Pascal DCT and the TonoPen appeared to be influenced by CCT, and this influence appeared to be greater for the latter.     

Comparison of Goldmann applanation tonometry, rebound tonometry and dynamic contour tonometry in normal and glaucomatous eyes

AIM: To compare the intraocular pressure (IOP) measurements obtained with the rebound tonometry (RT), dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in normal and glaucomatous eyes and investigate the effects of central corneal thickness (CCT) and corneal curvature (CC) on IOP measurements. METHODS: One hundred and twenty-four eyes of 124 subjects were enrolled in this cross-sectional study. Fifty-six of participants were healthy individuals and 68 of them were glaucomatous patients. IOP was measured on each subject always in the same order, ICare RT-Pascal DCT-GAT, after a minimum interval of 10min between measurements. CCT and CC were measured using a rotating Scheimpflug camera before the IOP measurements in all subjects. One way repeated measures ANOVA, Pearson correlation coefficient and regression analysis, and Bland-Altman analysis was used for the statistical assessment. RESULTS: Mean IOP for all enrolled eyes was 16.00±3.80 mm Hg for GAT, 16.99±4.91 mm Hg for RT, and 20.40±4.44 mm Hg for DCT. Mean differences between GAT and RT was -1.75±3.41 mm Hg in normal (P<0.001) and -0.37±3.00 mm Hg in glaucomatous eyes (P=0.563). Mean differences between GAT and DCT was -4.06±3.42 mm Hg in normal (P<0.001) and -4.67±3.12 mm Hg in glaucomatous eyes (P<0.001). GAT and RT were significantly positive correlated with CCT in normal (r=0.317, P=0.017 and r=0.576, P<0.001, respectively) and glaucomatous eyes (r=0.290, P=0.016 and r=0.351, P=0.003, respectively). DCT was also significantly positive correlated with CCT in normal eyes (r=0.424, P=0.001) but not in glaucomatous eyes (r=0.170, P=0.165). All tonometers were unaffected by CC. CONCLUSION: IOP measurements by RT and DCT were significantly higher than GAT. DCT has highest IOP measurements among these tonometers. RT was most influenced tonometer from CCT although all tonometers were significantly positive correlated with CCT except DCT in glaucomatous eyes. CC did not influence IOP measurements.     

Comparison of ICare tonometer with Goldmann applanation tonometer in glaucoma patients

PURPOSE: To compare the intraocular pressure (IOP) readings taken with the new ICare tonometer and with the Goldmann applanation tonometer (GAT) and to evaluate the influence of central corneal thickness (CCT) on the IOP measurements. PATIENTS AND METHODS: One eye of 178 consecutive patients with primary open-angle glaucoma underwent ultrasonic CCT measurement, followed by IOP evaluation with the GAT and with the ICare tonometer. The deviation of ICare readings from GAT values, corrected according to the Doughty and Zaman formula, was calculated and correlated to CCT by a linear regression model. The agreement between the 2 devices was assessed by use of the Bland-Altman method. RESULTS: The average CCT was 552+/-39 mum. The mean IOP and the mean corrected IOP with GAT were 19.4+/-5.4 mm Hg, and 18.5+/-5.7 mm Hg, respectively. The mean ICare IOP reading was 18.4+/-5.2 mm Hg. The deviations of ICare readings from corrected GAT values were highly correlated with CCT values (r=0.63, P<0.01). Linear regression analysis showed that a CCT change of 10 mum resulted in an ICare reading deviation of 0.7 mm Hg. The Bland-Altman scatter-plot showed a reasonable agreement between the 2 tonometers. CONCLUSIONS: The ICare tonometer can be useful in a routine clinical setting. The IOP readings are quite in accordance with those obtained by GAT. The measurements seemed to be influenced by CCT variations, and thus pachymetry should always be taken into consideration.     

Repeatability and accuracy of applanation resonance tonometry in healthy subjects and patients with glaucoma

Purpose: To evaluate the repeatability and accuracy of the applanation resonance tonometer (ART) used in the automatic servo‐controlled version, and to evaluate the influence of central corneal thickness (CCT) on the ART intraocular pressure (IOP) measurements. Methods: This prospective, randomized, single‐centre study included one eye of 153 subjects (35 healthy volunteers and 118 patients with glaucoma). All participants underwent ultrasonic CCT measurement, followed by IOP evaluation with Goldmann applanation tonometer (GAT) and ART in random order. A single operator measured the IOP with each tonometer three times. Intra‐examiner variability was evaluated using the coefficient of variation (CoV), intraclass correlation coefficient (ICC) and test–retest differences. Intermethod agreement was assessed using the Bland–Altman method. Linear regression analysis was used to evaluate the relationship between IOP measurements and CCT. Results: The mean IOP was 17.7 ± 4.4 mmHg with GAT and 20.6 ± 5.3 mmHg with ART (p < 0.001). CoV and ICC were, respectively, 5 ± 3% and 0.99 for GAT, and 8 ± 4% and 0.96 for ART (intermethods differences, p = 0.001). The ART test–retest differences significantly increased with increasing mean IOP (p = 0.003). The mean IOP difference (ART minus GAT) was 3.0 ± 4.0 mmHg, which increased with increasing mean IOP (p < 0.001). Both GAT IOP and ART IOP readings were significantly directly related to the CCT values (p = 0.03 and p = 0.004, respectively; intermethods difference, p = 0.32). Conclusions: The ART intra‐examiner repeatability was excellent, although significantly lower than that of GAT, and decreased at higher IOP levels. ART significantly overestimated GAT IOP measurements, especially at higher IOP range. Both GAT and ART appeared similarly influenced by CCT value.     

Effects of corneal thickness on intraocular pressure measured with three different tonometers

Purpose: To compare intraocular pressure (IOP) measured by a Goldmann applanation tonometer (GAT), a noncontact tonometer (NCT), and a portable noncontact tonometer (PNCT) in eyes of healthy volunteers, and to determine if a significant correlation exists between the IOP and the central corneal thickness (CCT). Methods: A total of 144 healthy participants were randomly assigned to one of two groups; in the first group, IOP was measured first with the NCT and then with the GAT. In the second group, IOP was measured first with the PNCT and then with the GAT. Subsequently, the CCT of all subjects was measured with an ultrasonic pachymeter. Results: The IOPs determined by the GAT and NCT and were strongly correlated, as were those determined by the GAT and PNCT, in both groups. However, a Bland-Altman plot showed that the correlations between the GAT and NCT and between the GAT and the PNCT measurements were not significant. With all three instruments, the IOP readings varied with the CCT. The mean IOPs obtained with the GAT increased by 0.23 mmHg with each 10-μm increase in CCT (0.23 mmHg/10 μm). The comparable value for the NCT was 0.29 mmHg/10 μm, and that for the PNCT was 0.31 mmHg/10 μm. Conclusions: For measurements of IOP in normal eyes, the GAT is the tonometer least affected by the CCT, compared with the PNCT and NCT. A PNCT is more likely to be affected by variations in CCT than the GAT.     

Precision and accuracy of the ICare tonometer – Peripheral and central IOP measurements by rebound tonometry

Purpose: The purpose of this study was to evaluate the ICare tonometers precision and accuracy and the extent to which intraocular pressure (IOP) measurements are influenced by measuring position. Methods: This was carried out by comparing the central and peripheral ICare‐IOP readings and comparing ICare‐ with the Goldmann applanation tonometer (GAT)‐IOP readings. IOP was measured using the ICare rebound tonometer on the right eye of 40 subjects, straight at the centre of the cornea (CS), straight 2 mm from the nasal and temporal limbus (NS and TS), and in 10 degrees nasally and temporally angled positions measured from the same location as CS (NA and TA). The IOP was also assessed with the GAT. Results: Central IOP (CS) was significantly (p < 0.001) greater than peripheral measurements (NS, TS, NA and TA) by approximately 3–4 mmHg. Centre IOP (CS) significantly overestimated by mean 2 mmHg and the peripheral measurements significantly underestimates approximately 1.4–2 mmHg compared with GAT readings. Conclusion: The ICare tonometer may be useful in a routine clinical setting for IOP screening, but the ICare measurement is not a substitute for the GAT measurement, when a precise and accurate IOP is desired.     

角膜厚度对三种不同眼压计测量的影响

目的:比较采用Goldmann压平眼压计(Goldmann applanation tonometer,GAT)、非接触眼压计(non-contact tonometer,NCT)和Schiotz眼压计(Schiotz tonometer,ST)的眼压(intraoeular pressure,IOP)测量,评估角膜中央厚度(central corneal thickness,CCT)对读数的影响。方法:使用GAT、NCT和ST对所有患者的右眼进行眼压测量。超声角膜厚度测量法测定CCT。所有IOP及CCT测量由同一检查者进行。计算CCT25%(Q1)百分位数和75%(Q3)百分位数值,并通过这种方法将该组分为薄、中、厚角膜亚组。使用Statplus软件进行统计分析。结果:全系列144眼,GAT测量平均IOP为17.4±4.9mmHg,NCT为16.0±5.8mmHg,ST为14.0±4.0mmHg(Friedman方差分析P<0.01)。IOP水平和CCT之间的相关系数NCT为0.787(P<0.01),GAT为0.630(P<0.01),ST为0.565(P<0.01)。ST测量中,纠正的IOP误差和CCT之间的相关性在厚角膜明显弱(r=0.381,P=0.022)。结论:NCT是最易受不同CCT影响的设备。ST读数似乎比GAT和NCT读数受CCT的影响小。特别是在厚角膜,与NCT和GAT相比,ST可以被认为是一个更可靠的仪器。     

Association between corneal hysteresis and central corneal thickness in glaucomatous and non‐glaucomatous eyes

Purpose: We aimed to determine corneal hysteresis values (CH) using the ocular response analyser (ORA) in non‐glaucomatous and glaucomatous eyes and their relationship with central corneal thickness (CCT). Methods: Corneal hysteresis, intraocular pressure (IOP) as measured by Goldmann applanation tonometry (GAT) and CCT were prospectively evaluated in 74 non‐glaucoma subjects with IOP < 21 mmHg and in 108 patients with treated primary open‐angle glaucoma (POAG). One eye in each subject was randomly selected for inclusion in the analysis. Results: Mean (± standard deviation [SD]) age was 59.2 ± 14.2 years in the non‐glaucoma group and 62.4 ± 9.8 years in the glaucoma group. Mean (± SD) GAT IOP was 15.7 ± 2.65 mmHg and 16.38 ± 2.73 mmHg in the non‐glaucoma and glaucoma groups, respectively. There was no statistically significant difference between the two groups in mean age (p = 0.396) or mean GAT IOP (p = 0.098). Mean (± SD) CH was 10.97 ± 1.59 mmHg in the non‐glaucoma and 8.95 ± 1.27 mmHg in the glaucoma groups, respectively. The difference in mean CH between the two groups was statistically significant (p < 0.0001). There was a strong positive correlation between CH and CCT in the non‐glaucoma group (r = 0.743) and a significantly (p = 0.001) weaker correlation (r = 0.426) in the glaucoma group. Conclusions: Corneal hysteresis was significantly lower in eyes with treated POAG than in non‐glaucomatous eyes. The corneal biomechanical response was strongly associated with CCT in non‐glaucoma subjects, but only moderately so in glaucoma patients. It can be assumed that diverse structural factors, in addition to thickness, determine the differences in the corneal biomechanical profile between non‐glaucomatous and glaucomatous eyes. Corneal hysteresis could be a useful tool in the diagnosis of glaucoma.     

Performance of the rebound,noncontact and Goldmann applanation tonometers in routine clinical practice

Purpose: To compare rebound tonometry (RBT) and noncontact tonometry (NCT) using Goldmann applanation tonometry (GAT) as reference. Methods: The study sample was comprised of 108 eyes of 108 subjects consecutively examined at a general ophthalmology clinic. The order of use of the three tonometers was randomized at the study outset. The difference between the methods was plotted against the mean to compare the tonometers. The hypothesis of zero bias was examined by a paired t‐test and 95% limits of agreement (LoA) were also calculated. Differences with respect to GAT were assessed according to the international standard for ocular tonometers (ISO 8612). Results: Mean intraocular pressures (IOPs ± SD) obtained using the three instruments were GAT 17.5 ± 3.8 mmHg; RBT 18.5 ± 5.5 mmHg and NCT 17.4 ± 5.6 mmHg. The 95% LoA were from ?7.9 to +7.7 mmHg for NCT–GAT and from ?6.8 mmHg to +8.7 mmHg for RBT–GAT. A difference with respect to GAT under ±1 mmHg was observed in 11.1% of the eyes measured by NCT and 18.5% of eyes measured by RBT. According to the IOP ranges established by the ISO 8612, differences from GAT measurements greater than ±5 mmHg were always above the accepted level of 5%. Correlations between IOP and central corneal thickness (CCT) were significant for all three tonometers. Conclusions: The rebound and noncontact tonometer behaved similarly when used to measure IOP taking GAT measurements as the reference standard. Neither tonometer fulfilled ISO 8612 requirements. Both were similarly influenced by CCT.     

The effect of contact lens-induced corneal edema on Goldmann applanation tonometry and dynamic contour tonometry

Purpose  To evaluate the effect of contact lens-induced corneal edema on intraocular pressure (IOP) measurements using Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) in Asian subjects. Participants  The study included 40 eyes of 20 normal volunteers with no evidence of ocular disease. Methods  Forty eyes of 20 healthy volunteers were required to wear soft contact lenses for 2 hours to induce corneal swelling. Central corneal thickness (CCT) and IOP were measured before and immediately after contact lens wear using specular microscope, GAT, and DCT. The IOP measurements by GAT and DCT were compared. The changes in the CCT and the IOP measurements after wearing contact lenses were assessed. Results  The mean CCT of the 40 eyes evaluated was 532.6 ± 31.6 μm. The mean IOP was 11.78 ± 2.04 mmHg for the GAT and 14.46 ± 1.89 mmHg for the DCT, and the difference was statistically significant (P < 0.001). After wearing contact lenses, the mean CCT was 553.2 ± 34.3 μm, which was 20.6 ± 12.9 μm greater than before wearing them (P < 0.001). The mean IOP measurements of the GAT and DCT were decreased after wearing the contact lenses. The mean decrease of the GAT values was 0.43 ± 1.95 mmHg, which was not statistically significant (P = 0.175). However, the mean decrease of the DCT readings, which was 0.75 ± 1.74 mm Hg, was statistically significant (P = 0.010). Conclusion  The IOP measurements with DCT were significantly higher than those with GAT in healthy Asian eyes. Although the mean IOP measurements of both the GAT and the DCT were decreased in the edematous cornea, IOP measurements of the DCT were more affected by corneal edema than were the GAT. The authors have no proprietary, commercial, or financial interests in any of the products described in this study.     

Corneal biomechanics measured with the ocular response analyser in patients with unilateral open‐angle glaucoma

Purpose: To evaluate the relationship between biomechanical properties of the cornea and intraocular pressure (IOP) and the role of biomechanical properties in eyes of patients with unilateral primary open‐angle glaucoma (POAG). Methods: The biomechanical properties of corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with the ocular response analyser (ORA). In an experimental setting, three human donor eyes with Schiotz‐tonometry‐controlled IOP were investigated. In addition, a series of patients with unilateral POAG were evaluated. Main outcome measures were CH, CRF, corneal‐compensated IOP (IOPcc), standard automated perimetry parameters mean defect (MD) and pattern standard deviation, central corneal thickness, Goldmann applanation tonometry (GAT), and cup‐to‐disc ratio. Results: A highly significant linear correlation between CH and the corneal‐compensated IOP (IOPcc, r = ?0.926; p < 0.001) was found. The correlation between IOP_CC and CRF was not significant (r = 0.335; p = 0.08). In total, 36 eyes of 18 patients with unilateral POAG were examined. Regarding uncorrected CH (mean 7.73 ± 1.46 mmHg glaucomatous eye and 9.28 ± 1.42 mmHg fellow eye), there was a highly significant difference between both eyes. This difference disappears, when CH was corrected for IOP (9.44 ± 3.78 mmHg and 9.97 ± 3.22 mmHg, respectively). Conclusions: Corneal hysteresis but not corneal resistance factor is dependent on IOP. In patients with unilateral POAG, IOP is higher in the affected eye. When CH is corrected for IOP, corneal biomechanical properties do not differ in both eyes of patients with unilateral POAG.     

Comparison of intraocular pressure measured by Pascal dynamic contour tonometry and Goldmann applanation tonometry

AIMS: To compare the intraocular pressure (IOP) measurements obtained using the Pascal dynamic contour tonometer (PDCT) with the standard Goldmann applanation tonometer (GAT) and to correlate these with central corneal thickness (CCT) in patients with normal corneas. METHODS: A prospective, masked, comparative case series of 116 eyes from patients attending a glaucoma clinic. IOP was measured with PDCT by one examiner and with GAT by a masked, independent examiner. A mean of six CCT readings was used for analysis. RESULTS: IOP measured by the two instruments correlated significantly (r=0.77; P<0.0001). IOP measured by GAT correlated strongly with CCT (r=0.37, P=0.0001) whereas the relationship between IOP measured by PDCT and CCT approached significance (r=0.17, P=0.073). The differences between GAT and PDCT measured IOP also correlated strongly with CCT (r=0.37, P<0.0001). The 95% limits of agreement between GAT and PDCT were +/-4.2 mmHg. Dividing the eyes into three groups on the basis of CCT, demonstrated those in the thickest tertile showed a poorer agreement between instruments and the GAT measured significantly higher IOP in this group (P=0.003) while the PDCT showed no significant differences with different CCTs (P=0.37). CONCLUSION: Demonstration of the relative independence of PDCT IOP measurements from CCT supports a potential clinical role for this instrument, particularly for subjects with CCT outside the normal range.     

动态轮廓眼压计在正常人群中的应用及其影响因素分析

目的评价动态轮廓眼压计（DCT）与Goldmann压平眼压计（GAT）测量值之间的关系,寻找DCT眼压测量值的影响因素;分析DCT所测眼压脉动振幅（OPA）与DCT眼压值、中央角膜厚度（CCT）、角膜屈光力（CCV）、眼轴长度（AL）、前房深度（ACD）、收缩压（SBP）、舒张压（DBP）和心率（HR）的关系。方法分别测量正常人60例60眼的DCT眼压、GAT眼压、CCT、CCV、AL、ACD以及HR、SBP、DBP等指标,比较GAT、DCT2种眼压计测量的相关性及DCT测量值的影响因素。结果 DCT与GAT所测眼压平均值分别为（16.04±2.57）mmHg和（14.20±2.93）mmHg。DCT眼压值较GAT眼压值高,差异有统计学意义（t=6.454,P〈0.01）。DCT眼压值与GAT眼压值呈正相关（r=0.684,P〈0.01）。DCT眼压值与CCT不相关（r=0.212,P=0.105）,GAT眼压值与CCT呈正相关（r=0.291,P=0.024）。60例正常人的OPA均值为（2.50±0.89）mmHg,OPA与年龄、DCT眼压值、CCT、SBP、DBP、HR均不相关（P〉0.05）,与CCV呈正相关（r=0.343,P=0.007）。结论在正常人群中DCT眼压值与GAT眼压值有较好的相关性,DCT的眼压测量值不受CCT、CCV等因素的影响。DCT眼压值、CCT、SBP、DBP、HR等对OPA无明显影响。