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.

Comparison of Intraocular Pressure via Goldmann-applanation Tonometry and TonoPen in Thyroid-associated Ophthalmopathy Accompanying Restrictive Strabismus

PURPOSE: To compare the intraocular pressure (IOP) measured using Goldmann-applanation tonometry (GAT) and Tonopen® tonometry and to evaluate the factors influencing the measurement difference in patients with thyroid-associated ophthalmopathy (TAO)-related restrictive strabismus. METHODS: In 50 eyes of 50 patients who were diagnosed with TAO, IOP measurements were taken using both GAT and a Tonopen® and were subsequently compared between the devices. Factors influencing the measurement difference between the devices were determined, including the restriction of eyeball movement, eyeball deviation, exophthalmometry, central corneal thickness, refractive errors, and blood thyroid hormone levels. RESULTS: In the TAO patients, the GAT-measured IOP was higher than for Tonopen® (16.1 ± 4.7 vs. 13.8 ± 4.5 mmHg, respectively, p < 0.001). As the restriction of vertical eyeball movement increased, the IOP difference between the devices also increased (p = 0.037). The absolute IOP difference between the devices was positively correlated with restrictions in vertical eyeball movement (p = 0.027), degree of vertical strabismus (p = 0.021), and central corneal thickness (p ≤ 0.031). CONCLUSIONS: In patients with TAO accompanying vertical eyeball movement restriction, potential errors in IOP measurements should be considered between the different IOP-measuring devices.

Comparison of Portable Tonometers and Goldmann Applanation Tonometer for Intraocular Pressure Measurement

PURPOSE: To compare the intraocular pressure (IOP) measured by portable rebound tonometer and TonoPen applanation tonometer with pressure measured by Goldmann applanation tonometer (GAT) and analyze the factors affecting IOP disagreement between tonometers. METHODS: In a prospective study of 463 eyes, IOP was measured with Icare Pro(R) rebound tonometer, TonoPen AVIA(R) applanation tonometer, and GAT. Bland-Altman plot, intraclass correlation coefficient, Pearson's correlation analysis, and multiple regression analysis were performed to evaluate the agreement of IOP measured by each tonometer and the factors affecting the measurements. RESULTS: The IOP values measured by Icare Pro(R) and TonoPen AVIA(R) were consistently higher than those measured by GAT, but showed no significant differences with those measured by GAT (p = 0.307 and 0.114, respectively). In Bland-Altman plot, the IOP values measured by Icare Pro(R) and TonoPen AVIA(R) exhibited excellent agreement with those measured by GAT. Both Icare Pro(R)/GAT and TonoPen AVIA(R)/GAT differences increased with younger age (p = 0.041 and 0.049, respectively) and higher central corneal thickness (p = 0.019 and 0.035, respectively). CONCLUSIONS: IOPs measured by portable Icare Pro(R) rebound tonometer and TonoPen AVIA(R) applanation tonometer were significantly correlated with IOP measured by GAT. Therefore, such instruments can be useful when measuring IOP with GAT is difficult. However, central corneal thickness and age should be considered when measuring IOP with portable tonometers.

Intraocular pressure measurements with the Tono-Pen XL® and Perkins® applanation tonometers in horses and cattle / Pressão intraocular medida com os tonômetros de aplanação Tono-Pen XL® e Perkins® em equinos e bovinos

The objective of this study was to compare the accuracy between two applanation tonometers, Tono-Pen XL® and Perkins®, in horses and cattle. The eyes of 20 horses and 20 cattle conscious and healthy were evaluated for the in vivo study and both eyes of 5 horses and 5 cattle were used as controls for the postmortem study. In conscious animals, the tonometry was performed with auriculopalpebral nerve block and then topical anesthesia for both tonometers and 1% fluorescein eye drops only for the Perkins tonometer. Readings of intraocular pressure (IOP) in the postmortem study were taken using manometry and tonometry by Tono-Pen XL® and Perkins®. The correlation coefficient (r²) between manometry and applanation tonometers Tono-Pen XL® and Perkins®, in horses, were 0.845 and 0.989, respectively, and in cattle, were 0.772 and 0.988, respectively. The mean IOP values in conscious horses with Tono-Pen XL® and Perkins® were 20.1±3.9mmHg and 20.9±3.2mmHg, respectively, and in conscious cattle, these values were 17.2±2.4mmHg and 17.9±1.4mmHg, respectively. There was a strong correlation between the IOP values obtained by direct ocular manometry and the Tono-Pen XL® and Perkins® tonometers in horses and cattle. There was no statistically significant difference between the mean IOPs obtained with both tonometers in conscious animals; however, there was a difference between the minimum values, which were on average 2-3 mmHg lower with the Tono-Pen XL® tonometer than with the Perkins® tonometer, which justifies a table of normal values differentiated for each tonometer.

O objetivo deste estudo foi comparar a acurácia entre dois tonômetros de aplanação, Tono-Pen XL® e Perkins®, em equinos e bovinos. Os olhos de 20 equinos e 20 bovinos conscientes e saudáveis foram avaliados para o estudo in vivo e ambos os olhos de 5 equinos e 5 bovinos foram usados como controle para o estudo post-mortem. Nos animais conscientes, a tonometria foi realizada com bloqueio do nervo auriculopalpebral e depois anestesia tópica para ambos os tonômetros e colírio de fluoresceína a 1% somente para o tonômetro de Perkins. Leituras da pressão intraocular (PIO) no estudo post-mortem foram realizadas utilizando manometria e tonometria pelo Tono-Pen XL® e Perkins®. O coeficiente de correlação (r²) entre a manometria e os tonômetros de aplanação Tono-Pen XL® e Perkins®, em equinos, foi de 0,845 e 0,989, respectivamente, e, em bovinos, foi de 0,772 e 0,988, respectivamente. Os valores médios de PIO nos equinos conscientes com Tono-Pen XL® e Perkins® foram 20,1±3,9mmHg e 20,9±3,2mmHg e, em bovinos conscientes, os valores foram de 17,2±2,4mmHg e 17,9±1.4mmHg, respectivamente. Houve uma forte correlação entre os valores obtidos de PIO pela manometria ocular direta e os tonômetros Tono-Pen XL® e Perkins® em equinos e bovinos. Entretanto, houve uma diferença entre os valores mínimos, em média 2-3mmHg menor com o tonômetro Tono-Pen XL® do que o tonômetro de Perkins®, o que justifica uma tabela de valores diferenciada para cada tonômetro.

Test retest variability of TonoPen AVIA.

The study was conducted to evaluate the intra-session repeatability of Tonopen AVIA (TPA). 180 eyes of 180 patients (50 eyes with glaucoma, 130 eyes of controls) were recruited for this observational study. The mean age of patients enrolled in the study was 43.9 ± 16.7 yrs (84 males, 96 females). Mean IOP recorded with Tonopen AVIA was 19.5 ± 9.5 mmHg, 19.4 ± 9.6 mmHg and 19.3 ± 9.2 mmHg, respectively in the first, second and third instances (P = 0.656). The intraclass correlation coefficient (ICC) ranged from 0.996 (95% CI: 0.956 - 0.998) for glaucoma subjects to 0.958 (95% CI: 0.934 - 0.975) for controls. The coefficient of variation in the study population ranged from 3.47% (glaucoma patients) to 8.10% (healthy controls), being 6.07% overall. The coefficient of repeatability varied between 2.96 (glaucoma patients), 3.35 (healthy controls) to 3.24 (overall). Thus, the Tonopen Avia shows good intrasessional repeatability of IOP in both glaucomatous patients and healthy subjects.

Comparison of Intraocular Pressures at Different Points in Human's Cornea before and after Laser in situ Keratomileusis with Tono-Pen Tonometer / 华中科技大学学报（医学）（英德文版）

In order to explore the difference of intraocular pressure (IOP) at different points of cornea before and after laser in situ keratomileusis (LASIK),IOP was measured by Tono-Pen Tonometer at central cornea,pericentral cornea and limbus respectively and analyzed statistically.After LASIK,IOP was dropped significantly at central cornea and pericentral cornea (P＜0.05),while no statistically significant change occurred at limbus (P＞0.05).There was no statistically significant difference in IOP at different points before LASIK (F=0.110,P=0.896),but statistically significant difference was found after LASIK (F=7.375,P=0.001).It was suggested that reliable IOP after LASIK could be obtained from the limbus by Tono-Pen tonometer.

Intraocular pressure as indicator of sympathetic asymmetry in the eyes / 国际眼科杂志(Guoji Yanke Zazhi)

·AIM: To determine the asymmetry in the sympathetic activity in the eyes as indicated by intraocular pressure (IOP).·METHODS: In a prospective cross sectional study, the IOP in 150 newborns, 80 young adults and 159 old people was measured with Tono-Pen under topical anaesthesia.·RESULTS:The meanIOP in the newborns was 16.16mmHg in right eye and 15.79mmHg in left eye; in young adults 15.04mmHg in right eye and 14.71 in left eye; in old people 15.16 in right eye and 15.03 in left eye.A statistically significant higher IOP was noted in the right eye in the newborns (P-0.03) and in young adults (P=0.02), but not in the old people (P=0.26). The higher IOP in the right eye indicates the lowered sympathetic activity in that eye.·CONCLUSION: We hypothesize that the sympathetic asymmetry in the bilaterally placed organs helps to establish the dominant pattern of the organ in the body.

A Study of the Tono-pen for Assessing Ocular Pressure in Patients with Headache Combined with Ocular Pain in the Emergency Department

PURPOSE: To study the use of the Tono-pen to estimate intraocular pressure (IOP) in patients with a headache combined with ocular pain in the emergency department (ED). METHODS: We carried out a prospective, single-centre study comparing the Tono-pen to the Goldmann tonometer in 31 patients. The two methods were compared according to measured IOP and diagnosis, and the results were analyzed for correlations. RESULTS: 31 patients (17 male, 14 female, mean age 51 years) were enrolled. The mean IOP according to the Tonopen and Goldmann were 19 mm Hg (95% CI: 14-25) and 18 mm Hg (95% CI: 12-23), respectively. The mean difference in measurement between the two was 1.8 mmHg. The 95% limits of agreement were -4.5 to 8.1 mmHg, and the correlation coefficient r was 0.976. In those patients with IOP > or = 25 mmHg, four (40%) were diagnosed of glaucoma. CONCLUSION: The Tono-pen was a very useful screening tool for patients presenting with headache combined with ocular pain in the ED.

Comparison of the Intraocular Pressure Measurement between Rebound Tonometer and Tonopen in Rats

PURPOSE: To compare the rebound tonometer with the TonoPen for measuring the intraocular pressure (IOP) in rats METHODS: Chronic IOP elevation models were induced unilaterally in nine Sprague-Dawley rats by applying an argon laser to the trabecular meshwork. IOP was measured before laser treatment and at one, two, and three days following laser treatment. Two independent operators collected five readings of the rebound tonometer and the TonoPen. Correlation analysis and comparison with the Bland & Altman method were performed. The intraclass correlation coefficient of each measurement and the difference between two independent operators were calculated. RESULTS: The IOP values measured with the rebound tonometer were well correlated with those of the TonoPen (r=0.676, p<0.001); however, the mean difference expressed as the percent difference of the averages of two tonometers, was 27.5%. The IOP values measured with a rebound tonometer exhibited a significantly higher intraclass correlation coefficient (0.966; 95% CI, 0.945-0.980 vs 0.412; 95% CI, 0.264-0.581) and a lower difference between the two operators (3.10+/-2.17 mmHg vs 6.17+/-5.17 mmHg) than those of the TonoPen. CONCLUSIONS: Although the IOP values measured with the rebound tonometer were lower than those of the TonoPen, they were in good agreement and were less variable than those of the TonoPen.

Application of Tono-Pen tonometer during Perioperative Period / 医疗卫生装备

Objective To introduce the clinical application of Tono-Pen tonometer.Methods The intraocular pressure was detected with Tono-Pen XL tonometer at different time points for sixteen patients went through laparoscopic gynecologic operation,then the statistical analysis of the results was performed.Results In processes of artificial pneumoperitoneum and low position,the intraocular pressure escalated gradually,and after artificial pneumoperitoneum,the intraocular pressure descended rapidly.Conclusion Tono-Pen tonometer is the only tonometer can be used for the patient of general anesthesia until now.

Normal Intraocular Pressure of Neonates Measured with Tono-pen

PURPOSE: It is difficult to estimate definite intraocular pressure of neonates. We intended to evaluate neonatal normal intraocular pressure using Tono-pen, and compared mean intraocular pressures between groups divided by sex, birth weight, and gestational age. METHOD: We measured the intraocular pressure with Tono-pen in 504 eyes of 252 newborn, who admitted in our hospital from June 2000 to January 2001 at their the second day of life. One observer measured the intraocular pressure with Tono-pen five to ten times after proparacain HCL 0.5% instillation on regular time. Only 5% of Tono-pen's coefficient of variance was considered valuable. Neonates suspected having congenital glaucoma or retinopathy were excluded. Conclusively, 462 eyes of 231 newborns were included. Mean gestational age was 38 weeks and 6 days. Mean birth weight was 3.23 kg. We achieved average intraocular pressures of neonates having gestational age between 38 weeks and 42 weeks, and birth weight between 3.0 kg and 3.5 kg. We achieved also average intraocular pressure of neonates divided by sex, gestational age, and birth weight, compared them with average intraocular pressure of normal neonates by 3-way ANOVA. RESULT: Average of intraocular pressure of normal neonates was 13.61+/-2.02 mmHg. Intraocular pressure of normal neonates is not statistically significant in the classification by sex, gestational age, and birth weight.(p-value>0.05) CONCLUSION: These value will aid the ophthalmologists in the diagnosis and screening of congenital glaucoma.

IOP & Corneal Diameter in Premature Infants

Premature infants may have underdevelopment of multiple organs including ocular structures.Sixty one premature infants of thirty seven weeks-old or younger were examed to note the correlation of intraocular pressure andcorneal diameter with gestational age and birth weight. Following topical anesthesia, intraocular pressure was measured with Tonopen II tonometer and the corneal diameter with caliper.The fundus was examed for the presence of risk factors for retinopathy of prematurity. Average gestational age of the subjects was 30.2 weeks (26~37 weeks), and birth weight was 1419 g (677~3691 g).Thirty five subjects had experienced oxygen therapy, and eleven patients were found to have any stage of retinopathy of prematurity. Average intraocular pressure was 10.8 +/-2.3 mmHg (mean +/-standard deviation), corneal diameter was 8.8 +/-0.5 mm.No significant correlation was found between intraocular pressure or corneal diameter and gestational age or birth weight.The presence of retinopathy of prematurity did not seem to influence the intraocular pressure and corneal diameter. Our results suggested that the growth in uterus did not seem to affect intraocular pressure or corneal diameter in gestational age of 26 to 37 weeks. These normative values may aid ophthalmologists in assesing intraocular pressure and corneal diameter in premature infants.

Comparison of Intraocular Pressure Measurements of Tono-Pen and Perkins Tonometer in Children Under the General Anesthesia

Tono-pne and Perkins tonometer have been widely accepted to measure the intraocular pressure(IOP) of children under the general anesthesia because of their portability. We evaluated the difference of IOP between two devices and the IOP variability in 39 children(77 eyes) under age 13 who had undergone surgery for strabismus or entropin under the general anesthesia. One observer measured the IOP three times alternately, and the order of measurement was randomized. Only 5% of Tono-pens coefficient of variance was considered valuable. The range of Tono-pen IOPs was 9~22mmHg, and the average was 15.41+/-3.23mmHg. The range of Perkins IOPs was 4~20 mmHg, with the average of 12.47+/-3.31mmHg. The difference between two methods on average was 2.94mmHg. Tono-pen IOPs were significantly greater than those recorded by Perkins tonometer, but both were within normal range. The IOP variability was not significantly different between two devices. Therefore both methods can be applied effectively in a clinical setting after sedation or general anesthesia of uncooperative children.

Effect of Premedication and Honan Balloon prior to Cataract Surgery on Intraocular Pressure measured by Tono-pen

With with use of Tono-pen, we investigated the degree of reduction in intraocular pressure of the Honan intraocular pressure reducer(HIPR) with preoperative use of dichlorphenamide and mannitol or without. Seventy five patients scheduled for cataract surgery were divided into 4 groups by preoperative medication. Intraocular pressure was measured before preoperative medication and in process of time after external compression with the Honan intraocular pressure reducer(HIPR) following retrobulbar injection. There was no additive effect on the reduction of intraocular pressure with the preoperative use of dichlorphenamide and mannitol. A rapid initial reduction in intraocular presure over the first 5 minutes of compression was followed by a more gradual reduction from 5 to 20 minutes. We concluded that the compression of up to 20 minutes duration without the preoperative use of dichlorphenamide and mannitol is adequate.

Comperieon of the Tono-Pen and the Goldmann Applanation Tonometry in Csreening Test

Tono-Pen was portable, miniaturized digital electronic tonometer. We compared Tono-Pen with Goldmann applanation tonometer through the mass screen studies on 634 eyes of 317 patients to evaluate the reliability of the Tono-Pen in determining intraocular pressure(IOP). We found 60% of the Tono-Pen readings to be within +/-1.5 mmHg of the Goldmann applanation tonometry readings and 85% to be within +/-2.5 mmHg difference. The correlation coefficient between the readings of the two instruments was 0.85. The Tono-Pen tonometry corresponded well to the Goldmann applanation tonometry in the 11 to 20 mmHg interval. We concluded that Tono-Pen tonometry is very useful in screening test to measure the intraocular pressure.

Clinical Comparison of the Pulsair Pneumotonometer, Oculab Tono-pen and Goldmann Applanation Tonometer

IOP was measured with 3 different tools, namely, the Pulsair peumotonometer(A), the Oculab Tono-pen(B), and the Goldmann applanation tonometer(C), in order to evaluate the clinical usefulness of each. 174 eyes without corneal opacity and corneal edema were measured. The results were as follows; 1. The correlation coefficient was 0.85(P20 mmHg)as measured by C(56 eyes), the correleation coefficient was 0.83 between A and C(P20 mmHg)as measurde by C, the sensitivity of A was 60.53% and that of B was 73.68%. According to this study, no significant difference could be found among these three tools. However, at low IOPs(20 mmHg as measured by the Goldman tonometer), the Oculab Tono-pen and Pulsair pneumotonometer tended to show lower values than the Goldmana applanation tono meter and the sensitivity of the Oculab Tono-pen showed higher than that of the Pulsair pneumotonomer.