This paper aims at providing an up-to-date review of principle and application of various tonometers, and analyzes the new techniques of diurnal IOP monitoring and design of sensor system abroad. Requirements and test methods for GB/T 14710-93.
Equipment Design ; Intraocular Pressure ; Tonometry, Ocular ; instrumentation ; methods

OBJECTIVE: To compare the corneal biomechanical properties among keratoconus, subclinical keratoconus and normal corneas by using CorVis ST, and to estimate the effect of these biomechanical indices in discriminating keratoconus and subclinical keratoconus from normal. METHODS: A total of 76 eyes of 67 subjects were enrolled and divided into three groups. Keratoconus group included 24 eyes from 17 patients, subclinical keratoconus group included 12 eyes from 12 patients and normal group included 40 normal eyes from 40 subjects．All the eyes were assessed with CorVis ST and ten biomechanical parameters, intraocular pressure (IOP) and central corneal thickness (CCT) were obtained from this machine. The discrimination of biomechanical characteristic of the three groups based on the all indices was reflected by discriminant analysis and the Fisher discriminant function was established. RESULTS: The values of corneal biomechanics of keratoconus, subclinical keratoconus, normal eyes were increased in sequence, except for three indices: the second applamation time (A2T), time taken to reach highest concavity (HCT) and maximum corneal velocity during the first applanation (Vin). Three sets of data were among a statistically significant difference (P<0.05). There were statistically significant differences (P<0.05) between any two groups by comparing with such two indices: radius value of central concave curvature at highest concavity (HCR) and CCT. The grades of the three groups were obvious, evaluated by the discriminant function. The accuracy of reevaluation was 85% by validation method. The biggest contribution of indices in discriminant function was given by such four indices in sequence: CCT, HCR, maximum deformation amplitude of highest concavity (HCDA) and maximum corneal velocity during the second applanation (Vout). CONCLUSION The corneal biomechanical properties of keratoconus and subclinical keratoconus were decreased compared with normal eyes. The biomechanical parameters based on CorVis ST showed a good performance for discriminating among keratoconus, subclinical keratoconus and normal corneas.
Biomechanical Phenomena ; Cornea ; Discriminant Analysis ; Humans ; Keratoconus ; Tonometry, Ocular

The detection and dynamic monitoring of intraocular pressure have important clinical significance for the diagnosis and treatment of glaucoma. The current status of clinical intraocular pressure detection and dynamic intraocular pressure monitoring are reviewed. The technical challenges encountered, and the shortcomings of the existing technology are analyzed, in order to expect better intraocular pressure monitoring technology to be applied to patients.
Glaucoma/diagnosis* ; Humans ; Intraocular Pressure ; Technology ; Tonometry, Ocular

Studies have been shown that intraocular pressure (IOP) shows a seasonal variation, but amount of change differs from study to study. The variability in their results may be due to negligence of factors that can affect IOP. Due to differences in environmental conditions of China than other countries, we investigated seasonal variations in IOP of 103 healthy male Chinese of Shanghai. IOP was measured each month over the course of fourteen months with the Goldmann applanation tonometer. The average intraocular pressures in the winter months were higher than those in the spring, summer, and autumn months. The IOP difference between winter and summer months was found to be 1.4 +/- 0.7 mmHg.This study confirms that season influences IOP. As compared to other nations, effect of seasons on IOP seems to be somewhat less pronounced in Chinese. The possible mechanisms, responsible for the seasonal variation of intraocular pressure, are also postulated.
Adult ; Analysis of Variance ; Blood Pressure ; China ; Humans ; Intraocular Pressure/*physiology ; Male ; Reference Values ; *Seasons ; Tonometry, Ocular

BACKGROUND: The purpose of the present study was to determine the effect of positive end-expiratory pressure on intraocular pressure under general anesthesia. METHODS: Contact tonometer HA-1 (Kowa, Japan) was used to measure the intraocular pressures of 22 subjects at zero end-expiratory pressure and positive end-expiratory pressure of 15 cmH2O under general anesthesia. The data were statistically analyzed by paired t-test. RESULTS: There is no statistically significant difference between intraocular pressure of zero end-expiratory pressure and positive end-expiratory pressure of 15 cmH2O in a population with normal basal ocular tonometry. CONCLUSIONS: Mechanical ventilation with positive end-expiratory pressure of 15 cmH2O under general anesthesia dose not present a clinically important significant risk for intraocular pressure increase in a population with normal basal ocular tonometry.
Anesthesia, General* ; Intraocular Pressure* ; Positive-Pressure Respiration* ; Respiration, Artificial* ; Tonometry, Ocular

Due to lack of the practical technique to measure the biomechanical properties of the ocular cornea in vivo, clinical ophthalmologists have some difficulties in understanding the deformation mechanism of the cornea under the action of physiological intraocular pressures. Using Young's theory analysis of the corneal deformation during applanation tonometry, the relation between the elasticity moduli of the cornea and the applanated corneal area and the measured and true intraocular pressures can be obtained. A new applanation technique has been developed for measuring the biomechanical properties of the ocular cornea tissue in vivo, which can simultaneously acquire the data of the applanation area and displacement of the corneal deformation as well as the exerted applanation force on the cornea. Experimental results on a rabbit's eyeball demonstrated that the present technique could be used to measure the elasticity moduli and creep properties of the ocular cornea nondestructively in vivo.
Animals ; Biomechanical Phenomena ; Cornea ; Elastic Modulus ; Intraocular Pressure ; Muscles ; Rabbits ; Tonometry, Ocular

Intraocular pressure detection has a great significance for understanding the status of eye health, prevention and treatment of diseases such as glaucoma. Traditional intraocular pressure detection needs to be held in the hospital. It is not only time-consuming to doctors and patients, but also difficult to achieve 24 hour-continuous detection. Microminiaturization of the intraocular pressure sensor and wearing it as a contact lens, which is convenient, comfortable and noninvasive, can solve this problem because the soft contact lens with an embedded micro fabricated strain gauge allows the measurement of changes in corneal curvature to correlate to variations of intraocular pressure. We fabricated a strain gauge using micro-electron mechanical systems, and integrated with the contact lens made of polydimethylsiloxane (PDMS) using injection molding. The experimental results showed that the sensitivity was 100. 7 µV/µm. When attached to the corneal surface, the average sensitivity of sensor response of intraocular pressure can be 125.8 µV/mm Hg under the ideal condition.
Contact Lenses, Hydrophilic ; Dimethylpolysiloxanes ; Glaucoma ; Humans ; Intraocular Pressure ; Tonometry, Ocular ; instrumentation

OBJECTIVE: To compare the difference in intraocular pressure (IOP) readings as well as the tolerability between Icare rebound tonometer (Icare RBT) and Goldmann applanation tonometer (GAT), and to evaluate the application of Icare RBT in monitoring the intraocular pressure in children after congenital cataract surgery. METHODS: The IOP was measured with the Icare RBT and GAT respectively in 150 children (262 eyes) after congenital cataract surgery by two experienced ophthalmologists. Correlation and Bland-Altman analysis were used to assess the agreement in IOP readings between the two instruments. The influence of the central corneal thickness (CCT) adjusted for age on IOP readings was analyzed by linear regression analysis. The tolerance of the patients to Icare RBT and GAT measurement were surveyed. RESULTS: The mean age was (44.82 ± 11.56) months in 150 children, including 81 boys and 69 girls. The mean IOP readings by the Icare RBT and GAT were (16.08 ± 5.72) mmHg and (14.17 ± 5.05) mmHg, respectively. The mean difference between the Icare RBT and GAT was (1.91 ± 2.04) mmHg, which was significantly correlated with CCT (r=0.409, P<0.001). The IOP readings by Icare RBT was significantly correlated with that measured by GAT(r= 0.936, P<0.001). The 95% confidence interval of the difference between the two instruments was ?2.10 to 5.91 mmHg. The Icare RBT examination was well tolerated by the children compared to the GAT examination. CONCLUSION The Icare RBT is easy to use and well tolerated by the children after congenital cataract surgery. Compared to GAT, the value measured by the IOPs trends to be overestimated. The difference in readings between the 2 tonometers will magnify with the increase in CCT.
Cataract ; congenital ; Cataract Extraction ; Child, Preschool ; Female ; Humans ; Intraocular Pressure ; Male ; Tonometry, Ocular ; instrumentation

The central corneal thickness (CCT) in age 48 years or less of Chinese was characterized and its relationship with gender, age, refraction and intraocular pressure (IOP) was investigated. Right eyes of 1669 participants were included in this study (880 men, 52.7% and 789 women, 47.3%). Mean age of the samples was 23.8 +/- 5.9 years. After the examination of corneal topography and refraction, Goldman applanation tonometry was carried out by one physician. Tonometric values were the mean of three consecutive readings. Subsequently, another physician carried out ultrasonic pachymetry with the DGH 2000 AP ultrasonic pachymeter. Six measurements were made at the center of the cornea of each eye. The mean value was used for analysis. The results showed that mean CCT of male participants was 551.33 +/- 34.62 microm, 5.79 microm more than that of female participants. Linear regression analyses revealed that CCT was negatively related with age only in female and no association was found between refractive status and CCT. IOP was positively related to CCT, and there was a difference in IOP of 1.5 mmHg (1 mmHg = 0.133 kPa) per 100 microm difference in CCT. Ocular hypertension group was prone to have thicker cornea than average. The results indicated that in adult Chinese CCT tended to decrease with aging in female only. IOP measured by Goldmann tonometry was positively related with CCT so that CCT should be measured along with IOP.
Age Factors ; China ; Cornea/*anatomy & histology ; Corneal Topography ; Intraocular Pressure ; Reference Values ; Sex Factors ; Tonometry, Ocular

OBJECTIVE: To investigate accuracy of the currently used strategies for intraocular pressure measurements for reflecting actual 24-hour intraocular pressure fluctuations. METHODS: From September, 2018 to January, 2019, the patients with a suspected diagnosis of primary open angle glaucoma at our hospital were prospectively enrolled to receive 24-hour intraocular pressure monitoring using a Goldmann tonometer. With the intraocular pressure measurements at 0:00, 2:00, 5:00, 7:00, 8:00, 10:00, 11:00, 14:00, 16:00, 18:00, 20:00, and 22:00 as the gold standard (strategy 1), we compared the measurements taken at 5:00, 7:00, 10:00, 14:00, 18:00, and 22:00 (strategy 2) and at 8:00, 11:00, 14:00, and 16:00 (strategy 3) for their accuracy in reflecting 24-h intraocular pressure fluctuations. RESULTS: A total of 41 patients (82 eyes) were enrolled in this study. The peak intraocular pressures measured using the 3 strategies were 21.09±4.15 mmHg, 20.54±4.10 mmHg, and 19.91±4.38 mmHg, respectively, showing significant differences among them ( CONCLUSIONS For suspected cases of glaucoma, intraocular pressure measurements at 4 and 6 time points of a day can not precisely reflect the actual range of intraocular pressure fluctuations, and may lead to a missed diagnosis of glaucoma.
Glaucoma/diagnosis* ; Glaucoma, Open-Angle ; Humans ; Intraocular Pressure ; Prospective Studies ; Tonometry, Ocular