Comparison of intraocular pressure measurement between rebound, non-contact and Goldmann applanation tonometry in treated glaucoma patients

Background: To compare the intraocular pressure readings obtained with the iCare rebound tonometer and the 7CR non‐contact tonometer with those measured by Goldmann applanation tonometry in treated glaucoma patients. Design: A prospective, cross‐sectional study was conducted in a private tertiary glaucoma clinic. Participants or Samples: One hundred nine (54 males : 55 females) patients including only eyes under medical treatment for glaucoma. Methods: Measurement by Goldmann applanation tonometry, iCare rebound tonometry and 7CR non‐contact tonometry. Main Outcome Measures: Intraocular pressure. Results: There were strong correlations between the intraocular pressure measurements obtained with Goldmann and both the rebound and non‐contact tonometers (Spearman r‐values ≥ 0.79, P < 0.001). However, there were small, statistically significant differences between the average readings for each tonometer. For the rebound tonometer, the mean intraocular pressure was slightly higher compared with the Goldmann applanation tonometer in the right eyes (P = 0.02), and similar in the left eyes (P = 0.93); however, these differences did not reach statistical significance. The Goldmann correlated measurements from the non‐contact tonometer were lower than the average Goldmann reading for both right (P < 0.001) and left (P > 0.01) eyes. The corneal compensated measurements from the non‐contact tonometer were significantly higher compared with the other tonometers (P ≤ 0.001). Conclusions: The iCare rebound tonometer and the 7CR non‐contact tonometer measure intraocular pressure in fundamentally different ways to the Goldmann applanation tonometer. The resulting intraocular pressure values vary between the instruments and will need to be considered when comparing clinical versus home acquired measurements.     

Clinical evaluation of two non-contact tonometers

The precision and speed of two non-contact tonometers were examined and compared. The Goldmann applanation tonometer was used as the standard for precision. On the average the results obtained with the non-contact tonometers were not significantly different from those obtained with the Goldmann tonometer. The variation in the values obtained with the non-contact tonometers was greater. The speed of measurement differed between the two non-contact tonometers.     

角膜厚度对两种眼压测量方法的影响

目的　比较非接触眼压计 (non -contacttonometer ,NCT)和Goldmann压平眼压计测量眼压的差异 ,并分别探讨中央角膜厚度 (centralcornealthickniss ,CCT)对这两种测量方法的影响。方法　对 1 0 8例拟接受PRK或LASIK手术的患者行CCT ,NCT和Goldmann压平计眼压测量。结果NCT和Goldmann压平眼压计测得的眼压均值具有显著性差异 (F =89 .70 4 4,P <0 . 0 1 )。CCT与NCT和Goldmann压平眼压计测量值呈正相关 ,相关系数分别是r =0. 4 96 0 (t =8 .356 3,P <0 .0 0 1 )和r =0 . 2 1 1 3(t =3. 1 6 2 3,P <0 .0 0 1 )。结论　NCT和Goldmann压平眼压计测量眼压值有差异 ,NCT测量值大于Goldmann压平眼压计 ,CCT对NCT的影响大于Goldmann压平眼压计。     

中央角膜厚度对3种眼压计眼压测量值的影响

目的比较分析不同中央角膜厚度(central corneal thickness,CCT)下Icare回弹式眼压计、Goldmann压平式眼压计(Goldmann applanation tonometer,GAT)和动态轮廓眼压计(dynamic contour tonometry,DCT)的眼压测量结果,探讨CCT对3种眼压计测量值的影响。方法 对78例患者152眼分别用Icare、GAT、DCT3种眼压计进行眼压测量,并进行CCT的测量,对比不同CCT下3种眼压计的测量结果,分析眼压测量值与CCT的关系。结果 在全部受测者中Icare、GAT、DCT测得的眼压均值分别为(19.16±5.03)mmHg(1 kPa=7.5 mmHg)、(18.41±4.52)mmHg和(17.23±3.69)mmHg,三者之间有显著差异(F=7.256,P=0.001)。Icare和GAT的眼压测量值均与CCT显著相关(r=0.341,P<0.001;r=0.333,P<0.001),CCT每改变10μm,Icare的眼压值改变0.47 mmHg,GAT的眼压值改变0.41 mmHg;而DCT的眼压测量值与CCT无显著相关(r=0.032,P=0.699)。结论 Icare、GAT的眼压测量值均明显受CCT的影响,而Icare受CCT影响的程度较GAT的稍大,DCT的眼压测量值基本不受CCT的影响。     

Intraocular pressure measurement in patients with instrastromal corneal ring segments.

PURPOSE: To study the measurement of intraocular pressure after implantation of Intacs (ICRS) intrastromal corneal ring segment, a device that is positioned circumferentially in the peripheral corneal stroma to correct myopia. The device changes the corneal curvature by shortening arc length. Since the ring segments are made of polymethylmethacrylate, this may cause localized changes in corneal elasticity so intraocular pressure measurement may be affected. METHODS: We measured the intraocular pressure of 12 eyes in which the ICRS had been in place longer than 6 months. We used Goldmann applanation and Tono-Pen tonometers over the central corneal and the paracentral corneal areas. We also measured the intraocular pressure with the Tono-Pen applanated directly over the intrastromal corneal ring segments. RESULTS: The resulting intraocular pressure measurements were similar for the Tono-Pen tonometer readings over the central cornea, paracentral cornea, and the Goldmann applanation tonometer readings over the central cornea (P < .01). Our measurements using the Goldmann applanation tonometer on the paracentral corneal area showed artificially elevated intraocular pressure in the 40 to 60 mmHg range. We were not able to obtain consistent results when we measured the intraocular pressure using the Tono-Pen on the corneal area directly overlying the intrastromal corneal ring segment implants. CONCLUSION: Consistent intraocular pressure measurements on eyes with the ICRS can be obtained with the Goldmann applanation tonometer over the central corneal area or with the Tono-Pen tonometer over the central or paracentral corneal areas.     

三种眼压计与Pentacam眼压校正系统的应用比较

目的:比较非接触式眼压计(NCT)、Goldmann压平式眼压计(GAT)、动态轮廓眼压计(DCT)和Pentacam三维眼前节分析系统四种方法检查眼压的差异,并研究它们与中央角膜厚度(CCT)和中央角膜曲率(CCV)的关系。方法:对拟行LASIK手术的143例286眼患者用Pentacam系统测量CCT和CCV后,分别用NCT,GAT和DCT测量眼压,并用Pentacam系统的Ehlers,Shah,Dresden,Orssengo/Pye和Kohlhaas5种眼压校正方法对NCT眼压值进行校正,将测量结果进行方差分析、相关性及线性回归分析。结果:DCT值最高,DCT与其他方法之间均有显著性差异(P<0.01);GAT与DCT,Kohlhaas,Shah之间有差异(P<0.05),与其他方法之间无差异;各组眼压值之间有较好的相关性,GAT与DCT的相关性最强(r=0.702);NCT受CCT影响最大,GAT受CCV影响最大,DCT,Dresden,Orssengo/Pye,Shah与CCT和CCV均不存在相关性(P>0.05)。结论:对CCT和CCV正常的健康人群进行青光眼筛查时建议使用压平式眼压计,对可疑的患者,尤其是CCT和CCV偏离正常的患者,宜进一步行DCT检查或者用Pentacam系统进行眼压校正。     

动态轮廓眼压计与压平眼压计的比较

目的:评价和比较动态轮廓眼压计和Goldmann压平眼压计测得的LASIK手术后眼压值。方法:接受准分子激光原位角膜磨镶术(LASIK)的近视患者34例68眼,分别于术前和术后3mo使用动态轮廓眼压计(Pascal dynamic contour tonometer,PDCT)和Goldmann压平眼压计(the Goldmann applanation tonometer,GAT)进行眼压测量。比较手术前后两种测量方法测得的眼压值的差异。多元线性相关分析研究GAT,PDCT测量值和角膜曲率及角膜中央厚度(CCT)之间的相关性。结果:LASIK手术后GAT测量值较术前低,而PDCT值和术前比较差异则无统计学意义。角膜曲率、CCT和GAT读数呈线性相关,而与PDCT读数无关。结论:GAT测量得到的眼压低于实际值。PDCT测眼压不受角膜曲率和中央角膜厚度影响。     

非接触眼压计的测量值探讨

比较眼压测量结果的不同取值方法 ,探讨非接触眼压计测量眼压的准确性。方法 :用非接触眼压计和压平眼压计测量 2 6 4例患者 ( 5 2 8只眼 )眼压 ,取非接触眼压计第一次测量值、三次均值和三次中的低值与压平眼压计比较。结果 :非接触眼压计测量眼压值与压平眼压计测得值密切相关 ,其中非接触眼压计三次测得值中的最低值与压平眼压计测得值最接近。结论 :非接触眼压计测量眼压应采用三次测量值的低值。     

Comparison of the ICare® rebound tonometer with the Goldmann tonometer in a normal population

The aim of this study was to evaluate the accuracy of measurement of intraocular pressure (IOP) using a new induction/impact rebound tonometer (ICare) in comparison with the Goldmann applanation tonometer (AT). The left eyes of 46 university students were assessed with the two tonometers, with induction tonometry being performed first. The ICare was handled by an optometrist and the Goldmann tonometer by an ophthalmologist. In this study, statistically significant differences were found when comparing the ICare rebound tonometer with applanation tonometry (AT) (p < 0.05). The mean difference between the two tonometers was 1.34 +/- 2.03 mmHg (mean +/- S.D.) and the 95% limits of agreement were +/-3.98 mmHg. A frequency distribution of the differences demonstrated that in more than 80% of cases the IOP readings differed by <3 mmHg between the ICare and the AT. In the present population the ICare overestimates the IOP value by 1.34 mmHg on average when compared with Goldmann tonometer. Nevertheless, the ICare tonometer may be helpful as a screening tool when Goldmann applanation tonometry is not applicable or not recommended, as it is able to estimate IOP within a range of +/-3.00 mmHg in more than 80% of the population.     

Tono-Pen眼压计与Goldmann眼压计的临床比较

目的:了解Tono-Pen眼压计的临床实用性。方法:62例(111只眼)随机先后用Tono-Pen眼压计与Goldmann眼压计进行眼压测量,比较两种眼压计测量值的差异。结果:111只眼中,用Goldmann眼压计测量的眼压平均值为(15.82±4.88)mmHg,用Tono-Pen眼压计测量的眼压平均值为(16.34±4.33)mmHg,两者有显著性差异。眼压在9～30mmHg范围时,两种眼压计的测量值之差为(-0.51±2.24)mmHg,差异无显著性。在眼压低于9mmHg时,有过高估计眼压的趋向;在眼压高于30mmHg时,有过低估计眼压的趋向。Tono-Pen眼压计与Goldmann眼压计的相关系数为0.865,呈密切相关。结论:Tono-Pen眼压计与Goldmann眼压计有很好的相关性,尤其是在眼压为9～30mmHg范围。眼科学报 2002;18:226-229.     

Effect of corneal parameters on measurements using the pulsatile ocular blood flow tonograph and Goldmann applanation tonometer

AIMS: To investigate the effect of central corneal thickness and corneal curvature on intraocular pressure measurements using the pulsatile ocular blood flow tonograph and the Goldmann applanation tonometer, and to assess the agreement between the pulsatile ocular blood flow tonograph and the Goldmann applanation tonometer in intraocular pressure measurement. METHODS: 479 subjects underwent intraocular pressure measurements with the Goldmann applanation tonometer and the pulsatile ocular blood flow tonograph. Of these, 334 patients underwent additional measurement of central corneal thickness with an ultrasonic pachymeter and corneal curvature measurement with a keratometer. RESULTS: The intraocular pressure measurements obtained with both the Goldmann applanation tonometer and the pulsatile ocular blood flow tonograph varied with central corneal thickness and mean keratometric reading. Intraocular pressure measured using the Goldmann applanation tonometer increased by 0.027 mm Hg per micro m increase in central corneal thickness. Intraocular pressure measured using the pulsatile ocular blood flow tonograph increased by 0.048 mm Hg per micro m increase in central corneal thickness. For an increase of 1 mm of mean corneal curvature there was rise in intraocular pressure of 1.14 mm Hg measured by the Goldmann applanation tonometer and of 2.6 mm Hg measured by the pulsatile ocular blood flow tonograph. When compared to the Goldmann applanation tonometer, the pulsatile ocular blood flow tonograph underestimated at low intraocular pressure and overestimated at higher intraocular pressure. CONCLUSION: Central corneal thickness and corneal curvature affected measurements obtained with the pulsatile ocular blood flow tonograph more than they affected measurements obtained with the Goldmann applanation tonometer.     

三种眼压计对维族和汉族大学生眼压测量值比较

目的：比较Goldmann眼压计、非接触式眼压计与Schiotz眼压计对维吾尔族、汉族大学生眼压测量值结果。

方法：横断面研究。分别采用Goldmann眼压计、非接触式眼压计与Schiotz眼压计测量维吾尔族、汉族大学生眼压。比较两族整体间、同族不同性别间、不同眼别间三种眼压计测得的眼压值。

结果：相同眼压计对维吾尔族及汉族大学生眼压测量值差异有统计学意义(P<0.05); 相同眼压计对同族不同性别间眼压测量值差异无统计学意义(P>0.05); 相同眼压计对不同眼别间眼压测量值差异无统计学意义(P>0.05),汉族学生比维吾尔族学生眼压测量值高(P<0.05),非接触式眼压计比Goldmann眼压计眼压测量值偏高(P<0.05),非接触式眼压计比Schiotz眼压计眼压测量值要小(P<0.05)。

结论：同一眼压测量仪对同族不同性别间及不同眼别间无差异,汉族学生比维吾尔族学生眼压测量值高,Schiotz眼压计眼压值测量结果显著高于非接触式眼压计,而非接触式眼压计眼压测量值高于Goldmann眼压计。     

On repeated corneal applanation with the Goldmann and two non‐contact tonometers

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.     

Assessment of true intraocular pressure: the gap between theory and practical data

A precise assessment of the intraocular pressure (IOP) is crucial for diagnosis and decision making regarding treatment modalities in patients with glaucoma. Recent epidemiologic studies show that a difference of only 1 mm Hg in the mean IOP may be critical enough to determine the visual field prognosis in patients with glaucoma. However, the Goldmann applanation tonometer, which is current gold standard, is not precise enough to measure the true IOP within an error of 1 mm Hg. There are many clinically proposed correction algorithms to correctly measure IOP. However, corrections using only the central corneal thickness and curvature may not be sufficient in each individual case. In this article, previously reported theoretical equations about the effects of corneal topography, modulus of elasticity, and tear film on Goldmann applanation tonometric IOP readings were reviewed, and their discrepancies with clinical or experimental data were analyzed. Thereafter, new tonometers such as the dynamic contour tonometer, the rebound tonometer, and the ocular response analyzer were compared with the Goldmann applanation tonometer and other popular tonometers.     

新型眼压计原理及其在临床中的应用

眼压测量是目前对青光眼进行疗效观察及随访的主要手段之一,眼压计是临床工作中测量眼压的重要工具,修氏眼压计和Goldmann 压平眼压计长期以来为国内外临床医生所广泛应用,近十年来,又出现了一些新型的眼压计,如动态轮廓眼压计（DCT）、I Care回弹眼压计、Tono-Pen眼压计、Diaton眼压计和Proview压眼闪光眼压计等。其原理各异,临床应用价值也众说纷纭。DCT与Goldmann 压平眼压计（GAT）有较好的相关性,且测量值不受角膜性状的影响,但其对于配合差者有较大误差。I Care回弹眼压计、Tono-Pen眼压计、Diaton眼压计和Proview压眼闪光眼压计均为便携式眼压计,测量时不需使用麻醉药,便于青光眼的筛查,但其临床应用较少,测量的准确性仍需进一步研究。（眼科,2012,21： 136-140）     

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.     

Pediatric intraocular pressure measurements: Tonometers,central corneal thickness,and anesthesia

Measuring intraocular pressure (IOP) is the cornerstone of a comprehensive glaucoma examination. In babies or small children, however, IOP measurements are problematic, cannot often be performed at the slit lamp, and sometimes require general anesthesia. Therefore, it is essential for an ophthalmologist who examines a pediatric patient to be aware of the different tonometers used in children, as well as the effects of central corneal thickness and anesthesia on IOP measurements. Goldmann applanation tonometry is the gold standard for IOP assessment. Most alternative tonometers tend to give higher IOP readings than the Goldmann applanation tonometer, and readings between different tonometers are often not interchangeable. Similar to Goldmann tonometry, many of these alternative tonometers are affected by central corneal thickness, with thicker corneas having artifactually high IOP readings and thinner corneas having artifactually lower IOP readings. Although various machines can be used to compensate for corneal factors (e.g., the dynamic contour tonometer and ocular response analyzer), it is important to be aware that certain ocular diseases can be associated with abnormal central corneal thickness values and that their IOP readings need to be interpreted accordingly. Because induction and anesthetics can affect IOP, office IOPs taken in awake patients are always the most accurate.     

Intraocular pressure measurement-comparison of dynamic contour tonometry and goldmann applanation tonometry

PURPOSE: The dynamic contour tonometer (DCT, Pascal tonometer, Swiss Microtechnology AG, Port, Switzerland) was recently introduced as a new method of intraocular pressure measurement, supposedly independent of corneal properties. In this study we analyzed the agreement and correlation of dynamic contour tonometry and Goldmann applanation tonometry (GAT) and investigated the influence of central corneal thickness (CCT) and corneal curvature. We also considered preferential patient groups for both methods. METHODS: In a prospective study of 100 eyes without glaucoma, intraocular pressure was measured using dynamic contour tonometry and Goldmann applanation tonometry, followed by measurements of central corneal thickness and corneal curvature. RESULTS: A clear correlation between dynamic contour tonometry and Goldmann applanation tonometry was found (r = 0.693; P < 0.001). Dynamic contour tonometry generally resulted in higher intraocular pressure measurements (median difference + 1.8 mm Hg, mean difference + 2.34 mm Hg). Unlike dynamic contour tonometry, Goldmann applanation tonometry was remarkably affected by central corneal thickness, but neither method was significantly influenced by corneal curvature. Bland-Altman graphs showed remarkable disagreement between dynamic contour tonometry and Goldmann applanation tonometry, which could be partially explained by the influence of central corneal thickness on Goldmann applanation tonometry. To obtain valid readings, dynamic contour tonometry required a more extensive selection of patients than Goldmann applanation tonometry. CONCLUSIONS: Dynamic contour tonometry seems to be a reliable method for intraocular pressure measurement, which unlike Goldmann applanation tonometry is not influenced by central corneal thickness. In clinical practice, advantages from dynamic contour tonometry can be expected for cooperative patients, outpatients, and patients with sufficient bilateral ocular fixation, whereas Goldmann applanation tonometry measurements are more reliable in case of patients with inadequate cooperation, poor vision, or nystagmus.     

Evaluation of intraocular pressure according to corneal thickness before and after excimer laser corneal ablation for myopia

Intraocular pressure is affected by corneal thickness and biomechanics. Following ablative corneal refractive surgery, corneal structural changes occur. The purpose of the study is to determine the relationship between the mean central corneal thickness (CCT) and the change in intraocular pressure measurements following various corneal ablation techniques, using different measurement methods. Two hundred myopic eyes undergoing laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) were enrolled into a prospective, non-randomized study. Corneal parameters examined included full ocular examination, measurement of CCT, corneal topography, corneal curvature and ocular refractivity. Intraocular pressure measurements were obtained using three different instruments—non-contact tonometer, Goldmann applanation tonometer and TonoPen XL (TonoPen-Central and TonoPen-Peripheral). All measurements were performed pre-operatively and 4 months post-operatively. Post-operative intraocular pressure was significantly lower than pre-operative values, with all instruments (p value < 0.001, Student's t-test). The post-operative intraocular pressure decrease was smallest using the Tonopen-XL compared to the Goldmann applanation tonometer and non-contact tonometer (p value < 0.001, ANOVA). Intraocular pressure readings are significantly reduced following corneal ablation surgery. We determined in our myopic patient cohort that the TonoPen XL intraocular pressure measurement method is the least affected following PRK and LASIK as compared to other techniques.     

New ways to measure intraocular pressure

PURPOSE OF REVIEW: In the last 10 years, several new means to measure intraocular pressure have emerged. This review covers recent findings concerning four new technologies: the ocular response analyzer, dynamic contour tonometry, rebound tonometry and the Proview phosphene tonometer. RECENT FINDINGS: The ocular response analyzer provides measurements of corneal biomechanics, including corneal hysteresis. Intraocular pressure readings from the ocular response analyzer have correlated well with Goldmann applanation tonometry and seem to be independent of corneal thickness in nonglaucoma patients; however, further studies are needed to determine whether this is true in glaucoma patients. Dynamic contour tonometry also appears to give pressure readings that are independent of corneal thickness. Rebound tonometry is convenient, can be used without topical anesthesia and appears to correlate well with Goldmann tonometry; however, pressure readings from rebound tonometry are not independent of corneal properties. Use of the Proview phosphene tonometer appears to decrease patient anxiety regarding their glaucoma; however, studies have not been supportive of its accuracy. SUMMARY: Dynamic contour tonometry provides intraocular pressure readings that are less dependent on corneal properties than Goldmann applanation tonometry. Rebound tonometry appears to correlate well with Goldmann tonometry and can be used without topical anesthesia.