Evaluation of the impedance tonometers TGDc-01 and iCare according to the international ocular tonometer standards ISO 8612

BACKGROUND: Two new tonometers have been introduced that are based on the impedance principle. Both the TGDc-01 (transpalpebral measurement) and the iCare (corneal measurement) do not require corneal anaesthesia. The present work presents an evaluation of both devices. METHODS: Comparative measurements using one of the new tonometers and applanation tonometry were performed by one investigator according to the international standard for ocular tonometer (ISO 8612). Measurements were performed on 445 eyes without corneal pathology from 243 patients. Six measurements were performed for iCare and 3 for TGDc, immediately followed by 3 applanation tonometry measurements. RESULTS: The correlation coefficient with respect to applanation tonometry was 0.81 for TGDc and 0.95 for iCare. TGDc-01 measurements showed an average deviation of 3.1 +/- 2.6 mmHg to those of Perkins applanation tonometry. The maximum difference was 28.7 mmHg below and 9.8 mmHg above the results of applanation tonometry. iCare showed an average deviation of 2.5 +/- 1.1 mmHg to Goldmann tonometry. The maximum difference was 14.5 mmHg below and 9.8 mmHg above. CONCLUSIONS: The results of both new tonometers showed a good correlation with the reference applanation tonometric methods, but the strict requirements of ISO 8612 are not fulfilled by either tonometer at present. Additionally, transpalpebral measurements with the TGDc-01 showed unacceptably high variability.     

Impact of corneal parameters on intraocular pressure measurements in different tonometry methods

AIM: To evaluate the impact of central corneal thickness (CCT) and corneal curvature on intraocular pressure (IOP) measurements performed by three different tonometers. METHODS: IOP in 132 healthy eyes of 66 participants was measured using three different tonometry techniques: Goldmann applanation tonometer (GAT), Pascal dynamic contour tonometer (DCT), and ICare rebound tonometer (RT). CCT and corneal curvature were assessed. RESULTS: In healthy eyes, DCT presents significantly higher values of IOP than GAT (17.34±3.69 and 15.27±4.06 mm Hg, P<0.0001). RT measurements are significantly lower than GAT (13.56±4.33 mm Hg, P<0.0001). Compared with GAT, DCT presented on average 2.51 mm Hg higher values in eyes with CCT<600 μm and 0.99 mm Hg higher results in eyes with CCT≥600 μm. The RT results were lower on average by 1.61 and 1.95 mm Hg than those obtained by GAT, respectively. Positive correlations between CCT in eyes with CCT<600 μm were detected for all IOP measurement techniques, whereas a similar relationship was not observed in eyes with thicker corneas. A correlation between IOP values and keratometry in the group with CCT<600 μm was not detected with any of the tonometry methods. In thicker corneas, a positive correlation was found for GAT and mean keratometry values (R=0.369, P=0.005). CONCLUSION: The same method should always be chosen for routine IOP control, and measurements obtained by different methods cannot be compared. All analysed tonometry methods are dependent on CCT; thus, CCT should be taken into consideration for both diagnostics and monitoring.     

Carotid–Femoral Pulse Wave Velocity Assessed by Ultrasound: A Study with Echotracking Technology

Described here is a new method for determination of carotid–femoral pulse wave velocity (PWV) based on arterial diameter waveform recording by an ultrasound system. The study was carried out on 120 consecutive patients. Carotid–femoral PWV was determined using a tonometric technique (PWVpp, PulsePen, DiaTecne, Milan, Italy) and an echotracking ultrasound system (PWVet, E-Track, Aloka, Tokyo, Japan). The relationship between PWVpp and PWVet was evaluated by linear regression and Bland–Altman analysis. There was excellent agreement between PWVet and PWVpp (Pearson's r = 0.94, 95% confidence interval: 0.91–0.96, p < 0.0001; PWVet = 0.88 × PWVpp + 0.57). The Bland–Altman plot revealed an offset of ?0.33 m/s with limits of agreement from ?2.21 to 1.54 m/s. The coefficients of variation for within-subject repeatability between PWVet and PWVpp had were 5.79% and 8.47%, respectively, without significant differences in the Bland–Altman analysis. The results suggest that echotracking technology can provide a reliable estimate of aortic stiffness comparable to that of the tonometric techniques.     

Intraocular pressure measurement over soft contact lens by rebound tonometer:a comparative study

AIM: To evaluate the intraocular pressure (IOP) measurements by Icare rebound tonometer over a contact lens in comparison with Goldmann applanation tonometry (GAT).METHODS: Fifty patients using contact lens were included in this study. One of the eyes of the patients was selected randomly and their IOP were measured by rebound tonometer with and without contact lens (RTCL, RT respectively) and by GAT, as well as their central corneal thickness (CCT) by optical pachymeter. The results of both methods were compared by correlation analysis, general linear method repeated measure and Bland-Altman analysis.RESULTS: Mean IOP values measured by RTCL, RT and GAT were 15.68±3.7, 14.50±3.4 and 14.16±2.8 (P<0.001), respectively. Mean IOP by RTCL was significantly higher than the measurements implemented by RT and GAT (P<0.001), while there was no difference between the measurements by GAT and RT (P=0.629). There was a good level of positive correlation between GAT and RTCL as well as RT (r=0.786 P<0.001, r=0.833 P<0.001, respectively). We have observed that CCT increase did not show any correlation with the differences of the measurements between RTCL and RT (P=0.329), RTCL and GAT (P=0.07) as well as RT and GAT (P=0.189) in linear regression model.CONCLUSION: The average of the measurements over contact lens by rebound tonometer was found to be higher than what was measured by GAT. Although this difference is statistically significant, it may be clinically negligible in the normal population.     

Icare回弹式眼压计的应用与护理

目的探讨Icare回弹式眼压计的临床应用以及测量时的护理。方法选取受试者112人112只眼,使用Icare回弹式眼压计分别对患者右眼角膜中央、距角膜缘2mill的0～180。子午线颞侧和鼻侧进行测量。结果Icare回弹式眼压计测得的眼压值在角膜中央、颞侧和鼻侧分别为（15．4±3．4）,（15．8±3．6）,（15．6±3．4）mmHg,角膜中央眼压和水平子午线的鼻侧、颞侧眼压数值比较差异无统计学意义（F=0．325,P〉0．05）,有显著的一致性。结论在正常眼压范围内,Icare回弹式眼压计在角膜中央、颞侧和鼻侧有明显的一致性。测量时的护理是取得准确测量结果的有效保证。     

Central corneal thickness in adult Chinese. Association with ocular and general parameters. The Beijing Eye Study

Background To evaluate the distribution of central corneal thickness and its associations in the adult Chinese population. Methods The Beijing Eye Study 2006 is a population-based study including 3,251 (73.3%) subjects (aged 45+ years) out of 4,439 subjects who participated in the survey in 2001 and who returned for re-examination. Central corneal thickness (CCT) measurements were performed by slit lamp-based optical coherence tomography. Results Central corneal thickness measurement data were available for 3,100 (95.4%) subjects. Mean CCT was 556.2±33.1 μm (median: 553 μm; range: 429–688 μm). In multiple regression analysis, CCT was significantly associated with optic disc area (P = 0.043), urban region (P < 0.001; odds ratio (OR): 4.77; 95% confidence interval (CI): 2.37, 7.17), male gender (P < 0.001; OR: 5.64; 95%CI: 2.57, 8.71), and intraocular pressure measurements (P < 0.001). It was not significantly associated with body weight (P = 0.54) and body height (P = 0.66), age (P = 0.17), and refractive error (P = 0.43). Intraocular pressure (measured by pneumotonometry) increased for each μm central corneal thickness increase by 0.03 mmHg. Conclusions In the adult Chinese population, CCT was significantly associated optic disc area, urban region, and male gender. Intraocular pneumotonometric pressure measurements increased for each μm increase in central corneal thickness by 0.03 mmHg. CCT was not associated with age and refractive error. Supported by Beijing Natural Science Foundation No 7071003, Beijing, China.     

动态轮廓眼压计监测LASIK手术前后眼压变化

目的比较动态轮廓眼压计(DCT)、Goldmann压平式眼压计(GAT)及非接触式眼压计(NCT)测量接受准分子激光原位角膜磨镶术(LASIK)患者眼压值的差异。设计前瞻性临床试验研究。研究对象接受LASIK治疗的近视患者70例(140眼)。方法对上述患者于术前、术后1周,1、6个月用三种不同眼压计分别测量眼压,比较各时间点、各种眼压计之间的差异。同时记录手术前、后中央角膜厚度,取其两者差为角膜切削深度的值。主要指标眼压值(IOP)和角膜切削深度。结果术后1周,1、6个月DCT测量值(16.74±1.96mmHg、16.67±1.90mmHg、16.42±2.12mmHg)与其术前值(17.36±2.32mmHg)比较差异无统计学意义(F=1.346,P=0.06)。术后GAT和NCT测量值均呈下降趋势,与术前测量值比较差异有统计学意义(GAT:F=101.217,P=0.000;NCT:F=171.466,P=0.000),并且下降值与角膜切削深度成正相关关系(GAT:r=0.86,P=0.000;NCT:r=0.87,P=0.000),但术后三个时间段测量值比较差异无统计学意义(GAT术后三个时间点q值为0.216、0.677、0.461,P值分别为0.461、0.097、0.117;NCT术后三个时间点q值为0.215、0.585、0.370,P值分别为0.436、0.436、0.100)。结论LASIK术后GAT和NCT测量值明显下降,而DCT测量值无显著变化,其测量值较前两者更为可靠。(眼科,2007,16:344-347)     

动态轮廓眼压计与Goldmann压平眼压计的临床应用比较

目的了解动态轮廓眼压计的临床实用性。方法67例患者134眼随即先后用动态轮廓眼压计与Goldmann压平眼压计进行眼压测量,比较两种眼压计测量值的差异。结果134眼中,用Goldmann压平眼压计测量的眼压平均值为(15.82±-4.88)mmHg,用动态轮廓眼压计测量的眼压平均值为(14.5±-4.33)mmHg,;两者无明显差异。但73%的患者的动态轮廓眼压计的眼压值高于Goldmann压平眼压计的测量值。两者的相关性为0.83。结论动态轮廓眼压计可以较好的反映患者的眼压,操作简便,值得推广应用。     

新型非接触式眼压分析仪ORA与Goldmann压平眼压计的比较

目的比较新型非接触式眼压分析仪ORA与Goldmann压平式眼压计测量眼压的差异,以评价ORA眼压测量仪在临床眼压测量中的应用价值。方法本院门诊127例237眼分别由专人进行非接触眼压测量仪ORA与Goldmann压平式眼压计测量,并同时用超声角膜测厚仪测量角膜厚度。结果127例病人237眼,Goldmann压平眼压值和ORA直接测量结果（IOPG）分别为（17.94±6.50）mmHg和（18.88±7.93）mmHg,两者比较差异有显著统计学意义（P=0.000）;正常人群平均角膜厚度为（546.19±36.34）μm,经角膜厚度-眼压公式校正IOPG平均值为17.42±3.92mmHg,ORA经自带软件处理后的眼压值（IOPcc）平均为（17.50±4.38）mmHg,两者比较差异无统计学意义（P=0.681）,IOPG校正前两者比较差异有统计学意义（P=0.024）。结论新型非接触式眼压分析仪ORA的直接测量值与Goldmann压平眼压计的测量值相近略高,ORA的测量分析值IOPcc是排除角膜因素影响更接近真实的眼压结果。     

美多丽-P诊断性散瞳前后眼压差异的研究

目的:观察用美多丽-P诊断性散瞳后眼压的变化情况。方法:选取2006-12/2007-02间在本院眼科门诊就诊患者56例(87眼),进行诊断性散瞳,散瞳前后用非接触式眼压计(NCT,Topcon CT-80A)分别进行眼压测量,比较散瞳前后眼压的差异。结果:活动性散瞳后双眼眼压均比散瞳前升高,两者差值分别为:右眼2.00±1.70mmHg,左眼1.77±1.94mmHg(P<0.001)差异具有统计学意义。对于同时进行双眼活动性散瞳的31例患者的左右眼间差异进行比较,差值为0.39±1.28mmHg,P>0.05无统计学意义。相同眼别,活动性散瞳前后进行相关性比较,右眼r=0.853,左眼r=0.806,P<0.01,具有统计学意义。结论:散瞳后可引起眼压的升高,甚至有诱发急性青光眼的可能,因此诊断性散瞳前对基础眼压的测量尤为重要,有利于保证医疗护理工作的安全。