In vivo assessment of the ocular biomechanical properties in patients with idiopathic normal pressure hydrocephalus.

PURPOSE: Idiopathic normal pressure hydrocephalus (iNPH) is associated with an increased prevalence of open-angle glaucoma, attributed to variations of the pressure gradient between intraocular and intracranial compartments at the level of the lamina cribrosa (LC). As ocular biomechanics influence the behavior of the LC, and a lower corneal hysteresis (CH) has been associated to a higher risk of glaucomatous optic nerve damage, in this study we compared ocular biomechanics of iNPH patients with healthy subjects. METHODS:  Twenty-four eyes of 24 non-shunted iNPH patients were prospectively recruited. Ocular biomechanical properties were investigated using the ocular response analyzer (Reichert Instruments) for the calculation of the CH, corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc). Results were compared with those of 25 eyes of 25 healthy subjects. RESULTS:  In iNPH eyes, the median CH value and interquartile range (IQR) were 9.7 mmHg (7.8-10) and 10.6 mmHg (9.3-11.3) in healthy controls (p = 0.015). No significant differences were found in IOPcc [18.1 mmHg (14.72-19.92) vs. 16.4 mmHg (13.05-19.6)], IOPg [15.4 mmHg (12.82-19.7) vs. 15.3 mmHg (12.55-17.35)], and CRF [9.65 mmHg (8.07-11.65) vs. 10.3 mmHg (9.3-11.5)] between iNPH patients and controls. CONCLUSIONS:  In iNPH patients, the CH was significantly lower compared to healthy subjects. This result suggests that ocular biomechanical properties may potentially contribute to the risk of development of glaucomatous optic nerve damage in iNPH patients.

Assessment of intraocular pressure measurement between Goldman applanation tonometer, rebound tonometer, non-contact tonometer, and its correlation with central corneal thickness.

Purpose: To compare readings of intraocular pressure (IOP) taken with the Goldmann applanation tonometer (GAT), the non-contact tonometer (NCT), and the rebound tonometer (RBT), and to compare their correlation with central corneal thickness (CCT). Methods: This was a prospective, cross-sectional, observational study to which patients above 18 years of age were enrolled. A total of 400 eyes of 200 non-glaucomatous patients underwent IOP recordings using the GAT, NCT, and RBT, and CCT was also noted. Informed consent of the patients was taken. The IOP readings taken via the three methods were compared and correlated with CCT. Paired t test was used to compare the two devices. Simple and multivariate linear regression analyses were used to study the relationship between factors. A P value less than 0.05 was considered significant. Correlation was determined using the Pearson correlation coefficient, and a Bland-Altman graph was plotted. Results: Mean IOP measured by the NCT was 15.65 ± 2.80 mmHg, by the RBT was 14.23 ± 3.05 mmHg, and by the GAT was 14.69 ± 2.97 mmHg. The mean CCT was 510.61 ± 33.83 microns. The difference between mean IOP recorded by the NCT and that by the RBT was 1.41 ± 2.39 mmHg, between the NCT and GAT was 0.95 ± 2.03 mmHg, and between the GAT and RBT was 0.45 ± 2.22 mmHg. The difference between the IOP values was statistically significant (P < 0.005). All tonometers showed a statistically significant correlation with CCT, but it was observed that the NCT had a stronger correlation (0.4037). Conclusion: The IOP readings taken by all the three methods were comparable; however, RBT values were closer to GAT values. CCT did influence the IOP values, and this should be kept in mind while evaluating.

Corneal Biomechanics Assessment with Ultra High Speed Scheimpflug Camera in Primary Open Angle Glaucoma Compared with Healthy Subjects: A meta-analysis of the Literature.

PURPOSE: The aim of this meta-analysis of the literature is to provide a comprehensive analysis of the differences in Corvis ST dynamic corneal response (DCR) parameters between primary open-angle glaucoma (POAG) patients and healthy controls. METHODS: A quantitative meta-analysis was conducted on articles published before September 10, 2021 identified by searching PubMed, EMBASE, and Web of Science. Prospective studies comparing DCR Corvis ST parameter in high tension POAG and healthy controls were included. The random-effects model was conducted. Assessment of heterogeneity was based on the calculation of I2. Funnel plots evaluation and meta-regression were performed in case of detection of high heterogeneity. RESULTS: The selection process resulted in the inclusion of six articles. Pooled analysis revealed that POAG corneas respond to mechanical stimulus with a smaller concavity, showing lower deformation amplitude (DA) (CI95% -0.991 to -0.578; p < .001; I2 = 0%), higher highest concavity radius (HCR; confidence interval [CI]95% -0.01 to 0.34; p = .058; I2 = 6.7%), and lower peak distance (PD; CI95% -1.06 to -0.024; p = .040; I2 = 86.5%). They also show a slower loading phase, with lower highest concavity time (HCT; CI95% -0.39 to -0.02; p = .029; I2 = 3.3%) and lower applanation velocity-1 (CI95% -0.641 to -0.127; p = .003; I2 = 34.6%), and a faster restoration to the original form, shown by lower applanation time-2 (CI95% -1.123 to -0.544; p = .001; I2 = 44.8%) compared to healthy subjects. CONCLUSIONS: High tension POAG patients are characterized by stiffer corneas compared to healthy controls. These differences are valid also after removing the effect of age, corneal thickness, and intraocular pressure (IOP).

Assessment of temporal and spatial distribution patterns of aerosol produced by air-puff non-contact tonometer.

PURPOSE: To assess the distribution pattern of aerosol in the aspect of time and direction during the intraocular pressure (IOP) measurement by air-puff non-contact tonometer (NCT) and further offer references for protection from coronavirus disease-19 (COVID-19) in the routine ophthalmic examination. METHOD: A single-center observational study was conducted in the ophthalmology clinics of Peking University Third Hospital. Two air quality detectors were equipped to assess the generated particulate matter (PM) concentration simultaneously within 30 s after IOP measurement in the outpatient hall. Detector A was fixed next to the NCT as a reference, while Detector B was fixed 1 meter away. The participants were divided into two groups depending on the position of Detector B. The generation of aerosol was compared within different groups and time intervals. RESULTS: 144 participants were enrolled in the final analysis. At a 1 m distance from the NCT, the PM2.5 concentration significantly increased at the 30 s (Z = 2.898, Bonferroni-corrected P = 0.038) while the PM10 concentration increased immediately after the IOP measurement (Z = 2.967, Bonferroni-corrected P = 0.030). The PM2.5 and PM10 concentrations at 1 m were significantly higher immediately (Z = -2.183, P = 0.029; Z = -2.502, P = 0.012) and 30 s (Z = -2.021, P = 0.043; Z = -2.071, P = 0.038) after the IOP measurements when the Detector B was vertical to the air jet on the lateral side. CONCLUSIONS: NCT may produce aerosol after the IOP measurement by air-puff. The generated PM2.5 had a prolonged existence compared with PM10 at a 1 m distance. The lateral side of the air-puff direction may be of higher exposure risk to aerosol.

Assessment of corneal biomechanics, tonometry and pachymetry with the Corvis ST in myopia.

To evaluate the repeatability of Corvis ST corneal biomechanical, tonometry and pachymetry measurements, and agreement of pachymetry measures with the Pentacam HR and RTVue OCT. Three consecutive measurements of the right eye of 238 myopic subjects were acquired with the Corvis ST, Pentacam HR, and RTVue OCT. Repeatability of Corvis ST was evaluated by within-subject standard deviation [Sw] and repeatability limit [r]. The agreement of central corneal thickness (CCT) measurements were compared among the three instruments using the Bland-Altman limits of agreement. Comparisons were further stratified by CCT (Corneathin ≤ 500 µm; Corneanormal = 500-550 µm; Corneathick > 550 µm). Sw was below 1 mmHg in Corneathin, Corneanormal, and Corneathick groups for IOP and bIOP. Sw for SP-A1 were 4.880, 6.128, 7.719 mmHg/mm respectively. Sw for CBI were 0.228, 0.157, 0.076, and correspondingly Sw for TBI and SSI were 0.094 and 0.056, 0.079 and 0.053, 0.070 and 0.053. The Bland-Altman plots for CCT implied poor agreement with mean differences of 29.49 µm between Corvis and OCT, 9.33 µm between Pentacam and OCT, and 20.16 µm between Corvis and Pentacam. The Corvis ST showed good repeatability with the exception of CBI in the various CCT groups. The CCT measured by Corvis ST was not interchangeable with Pentacam HR and RTVue OCT.

Longitudinal assessment of optic nerve head changes using optical coherence tomography in a primate microbead model of ocular hypertension.

In humans, the longitudinal characterisation of early optic nerve head (ONH) damage in ocular hypertension (OHT) is difficult as patients with glaucoma usually have structural ONH damage at the time of diagnosis. Previous studies assessed glaucomatous ONH cupping by measuring the anterior lamina cribrosa depth (LCD) and minimal rim width (MRW) using optical coherence tomography (OCT). In this study, we induced OHT by repeated intracameral microbead injections in 16 cynomolgus primates (10 unilateral; 6 bilateral) and assessed the structural changes of the ONH longitudinally to observe early changes. Elevated intraocular pressure (IOP) in OHT eyes was maintained for 7 months and serial OCT measurements were performed during this period. The mean IOP was significantly elevated in OHT eyes when compared to baseline and compared to the control eyes. Thinner MRW and deeper LCD values from baseline were observed in OHT eyes with the greatest changes seen between month 1 and month 2 of OHT. Both the mean and maximum IOP values were significant predictors of MRW and LCD changes, although the maximum IOP was a slightly better predictor. We believe that this model could be useful to study IOP-induced early ONH structural damage which is important for understanding glaucoma pathogenesis.

Evaluation and treatment of glaucoma 24hours a day. Where are we and where are we going? / Evaluación y tratamiento del glaucoma durante las 24 horas del día. ¿Dónde estamos y hacia dónde vamos?

Current management of glaucoma generally involves medical, laser, or surgical treatment in order to achieve an intraocular pressure (IOP) control which is commensurate with either stability or delayed progression of the disease. Although the follow-up of glaucoma patients is usually carried out with sporadic and isolated intraocular pressure measurements, the literature already indicates that this might not the best option to manage glaucoma patients. This article reviews the importance of 24hours intraocular pressure monitoring based on studies and publications that exist in this regard to date. A critical review on the methodology of these publications has been conducted. The need is stressed for further studies on the intraocular pressure patterns in different types of glaucoma, as well as the pattern with different therapies used in glaucoma aimed at optimising the management of the disease.

Assessment of glaucoma referral letter for quality and accuracy among patients referred to a tertiary eye care center.

Purpose: To assess the quality and accuracy of glaucoma referrals from ophthalmologist. Methods: Retrospective review of patients chart with referral letter to a tertiary glaucoma center between January and December 2017. Patients aged <16 years, lens-induced glaucoma, uveitic glaucoma, and glaucoma following retinal and corneal surgery were excluded. Results: A total of 184 patients referred by 55 ophthalmologists were included. Mean patient age (SD) was 57.8 ± 14 years. Intraocular pressure was not documented in the referral letter in 113 (61%) patients, gonioscopy in 174 (95%) patients, disc findings in 149 (81%) patients, and visual fields in 175 (95%) patients. Thirteen (37%) of the 35 patients referred as open angle glaucoma were found to have angle closure glaucoma. Pseudoexfoliation glaucoma was diagnosed in 29 (16%) patients, of which 18 were missed by the referring ophthalmologist. Conclusion: In our study >90% of referral letter did not have the essential parameters. A standard template for glaucoma referral is suggested, which will help the patient to get better transfer of care.

Corneal biomechanics and intraocular pressure assessment after penetrating keratoplasty for non keratoconic patients, long term results.

BACKGROUND: To evaluate corneal biomechanical properties by the Ocular Response Analyzer (ORA) in non keratoconic patients underwent penetrating keratoplasty (PK). METHODS: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann- correlated intraocular pressure (IOPg), cornea-compensated IOP (IOPcc) using the ORA, and central graft thickness (CGT) were measured in 30 eyes at least two years after penetrating keratoplasty for non keratoconic indications. IOP using the Goldmann applanation tonometer (GAT) was also obtained after compensation for graft thickness and astigmatism. RESULTS: The mean age of patients was 33.1 ± 10.13 years; indications for PK were herpetic corneal scar (53.3%), corneal stromal dystrophy (23.3%), traumatic corneal opacity (10%), chemical corneal opacity (6.7%), and Fuchs endothelial dystrophy (6.7%). Mean CH and CRF were 8.52 ± 1.81 mmHg, and 8.56 ± 1.59 mmHg, respectively. Mean CGT was 532.43 ± 30 µm. Mean IOP GAT, IOPg, and IOPcc were 11.88 ± 3.66, 14.64 ± 4.08, and 17.27 ± 4.60 mmHg, respectively (P < 0.001). No significant association was found between CGT and IOP readings obtained using either the ORA or GAT. There were significant negative association between CH with both IOP GAT and IOPcc, while CRF had significant positive association with IOPg. CONCLUSION: After penetrating keratoplasty for non keratoconic patients, graft biomechanics does not return to average values even 2 years after the operation; moreover, intraocular pressure measurement with ORA gives higher values than thickness compensated GAT.

Assessment of corneal and fatty tissues biomechanical response in dynamic tonometry tests by using inverse models.

PURPOSE: The assessment of corneal biomechanics is essential for studying ophthalmological operations, such as refractive surgeries, and for more accurate estimation of intraocular pressure. The chief aim of the current study is to characterize corneal and fatty tissues in order to construct a model to predict eye globe behavior during dynamic tonometry tests. METHODS: In the present study, images from corneal deformation, acquired from Corvis ST tonometer, were processed. Then, corneal pure displacement and eye globe retraction were calculated. Utilizing inverse finite element method, corneal material properties were calculated in order to predict pure deformation obtained from Corvis ST. Using a similar approach, material parameters of fatty tissue were estimated in order to predict the eye globe retraction. The model used for fatty tissue was considered as corneal boundary condition in a forward finite element model to create a joint model, which could simulate corneal behavior in dynamic tonometry tests. RESULTS: It was shown that an isotropic material model is accurate enough to predict corneal deformation in dynamic tonometry tests. Moreover, effects of IOP on the estimated material properties were investigated. Finally, utilizing the joint model, it was demonstrated that there is strong correlation between corneal stiffness and the biomechanical parameter introduced by Corvis ST. CONCLUSIONS: An eye globe model was constructed and characterized by two distinct inverse models for corneal and fatty tissue. This model can be utilized for predicting eye globe behavior during dynamic tonometry tests besides other ophthalmological operations.

[Ease of handling of first and second generation rebound tonometers]. / Handhabung von Reboundselbsttonometern der ersten und zweiten Generation.

PURPOSE: To evaluate the ease of handling of two rebound tonometers, which are designed for self-measurement of intraocular pressure (IOP) in a clinical setting by untrained patients. METHODS: After self-measurement of the IOP with the rebound tonometers iCare ONE and iCare HOME, participants were asked to complete a questionnaire containing different subitems concerning ease of operation using a visual analog scale (1 = very good to 5 = very poor). Moreover, the feasibility and duration of measurement were tested. RESULTS: A total of 147 subjects participated in this study. The mean score for general handling ability was 2.79 ± 1.01 for the iCare ONE and 1.85 ± 0.87 for the iCare HOME (p < 0.001). The evaluation of the subitems sense of safety (iCare ONE: 2.71 ± 1.03 and iCare HOME: 1.87 ± 0.81, p < 0.001) and comfort of measurement (iCare ONE: 2.07 ± 1.01 and iCare HOME: 1.66 ± 0.72, p < 0.001) also showed a significant discrepancy between the two tonometers. Participants needed significantly less time for a single valid measurement when using the iCare HOME tonometer (mean 66.14 ± 61.54 s) compared to the iCare ONE tonometer (mean 81.54 ± 69.51 s, p < 0.001). CONCLUSIONS: A better handling of the iCare HOME rebound tonometer in comparison to the iCare ONE tonometer can be deduced on the basis of the subjective assessments of patients and the shorter duration of measurements. Moreover, the iCare HOME received a significantly better evaluation for all subitems. The accuracy of measurements using the iCare HOME still needs to be clarified.

Quantitative assessment of corneal vibrations during intraocular pressure measurement with the air-puff method in patients with keratoconus.

BACKGROUND: One of the current methods for measuring intraocular pressure is the air-puff method. A tonometer which uses this method is the Corvis device. With the ultra-high-speed (UHS) Scheimpflug camera, it is also possible to observe corneal deformation during measurement. The use of modern image analysis and processing methods allows for analysis of higher harmonics of corneal deflection above 100 Hz. METHOD: 493 eyes of healthy subjects and 279 eyes of patients with keratoconus were used in the measurements. For each eye, 140 corneal deformation images were recorded during intraocular pressure measurement. Each image was recorded every 230 µs and had a resolution of 200 × 576 pixels. A new, original algorithm for image analysis and processing has been proposed. It enables to separate the eyeball reaction as well as low-frequency and high-frequency corneal deformations from the eye response to an air puff. Furthermore, a method for classification of healthy subjects and patients with keratoconus based on decision trees has been proposed. RESULTS: The obtained results confirm the possibility to distinguish between patients with keratoconus and healthy subjects. The features used in this classification are directly related to corneal vibrations. They are only available in the proposed software and provide specificity of 98%, sensitivity-85%, and accuracy-92%. This confirms the usefulness of the proposed method in this type of classification that uses corneal vibrations during intraocular pressure measurement with the Corvis tonometer. DISCUSSION: With the new proposed algorithm for image analysis and processing allowing for the separation of individual features from a corneal deformation image, it is possible to: automatically measure corneal vibrations in a few characteristic points of the cornea, obtain fully repeatable measurement of vibrations for the same registered sequence of images and measure vibration parameters for large inter-individual variability in patients.

Quantitative assessment of responses of the eyeball based on data from the Corvis tonometer.

BACKGROUND: The "air-puff" tonometers, include the Corvis, are a type of device for measuring intraocular pressure and biomechanics parameters. The paper attempts to analyse this response and its relationship with other parameters measured in the Corvis tonometer. METHODS: A number of 13,400 2D images were acquired from the Corvis device and analysed (32 healthy and 16 ill people). A new method has been proposed for the analysis of responses of the eyeball based on morphological transformations and contextual operations. RESULTS: The proposed algorithm enables to determine responses of the eyeball to an air puff coming from the Corvis tonometer. Additionally, responses of the eyeball have been linked to some selected features of corneal deformation. The results include, among others: (1) distinguishability between the left and right eye with an error of 7%; (2) the correlation between the area under the curve in corneal deformation and the response of the eyeball -0.26; (3) the correlation between the highest concavity time and the maximum deformation amplitude of 0.4. All these features are obtained fully automatically and repetitively at a time of 3.8s per patient (Core i7 10GB RAM). DISCUSSION: It is possible to measure additional parameters of the eye deformation which are not available in the original software of the Corvis tonometer. The use of the proposed methods of image analysis and processing provides results directly from the eye response measurement when measuring intraocular pressure.

Scheimpflug camera in the quantitative assessment of reproducibility of high-speed corneal deformation during intraocular pressure measurement.

The paper presents an original analysis method of corneal deformation images from the ultra-high-speed Scheimpflug camera (Corvis ST tonometer). Particular attention was paid to deformation frequencies exceeding 100 Hz and their reproducibility in healthy subjects examined repeatedly. A total of 4200 images with a resolution of 200 × 576 pixels were recorded. The data derived from 3 consecutive measurements from 10 volunteers with normal corneas. A new image analysis algorithm, written in Matlab with the use of the Image Processing package, adaptive image filtering, morphological analysis methods and fast Fourier transform, was proposed. The following results were obtained: (1) reproducibility of the eyeball reaction in healthy subjects with precision of 10%, (2) corneal vibrations with a frequency of 369 ± 65 Hz (3) and amplitude of 7.86 ± 1.28 µm, (4) the phase shift within two parts of the cornea of the same subject of about 150°. The result of image sequence analysis for one subject and deformations with a corneal frequency response above 100 Hz.

[New algorithm of aqueous humor dynamics assessment in glaucoma].

The purpose of the study was to develop a new algorithm of aqueous humor dynamics assessment in glaucomatous eyes, which would take into account the shape of the tonographic curve and individual elastic properties of the corneoscleral capsule. Basic ophthalmic examination supplemented with tonography and differentiated tonometry was performed on 33 patients with primary open-angle glaucoma (POAG), 8 POAG suspects, and 9 healthy controls. Obtained data were processed in accordance with the developed algorithm. A new formula for calculating the coefficient of outflow facility and several additional parameters describing the condition of aqueous pathways were proposed. In POAG patients these parameters significantly differed from those in healthy controls.

Prevalence of increased intraocular pressure and optic disk cupping: multicenter glaucoma screening in Israel during the 2009 and 2010 World Glaucoma Weeks.

BACKGROUND: Early detection of glaucoma enables early initiation of treatment. Screening populations at risk is likely to help achieve this goal. OBJECTIVES: To increase public awareness regarding early detection of glaucoma, and estimate the prevalence of increased intraocular pressure (IOP) and optic disk cupping in the screened population. METHODS: A public awareness campaign was carried out in Israel during the 2009 and 2010 World Glaucoma Week, culminating each year in a one-day, free-of-charge screening of individuals in 13 outreach public locations. Screening was performed by 45 ophthalmologists and included a brief medical history, slit-lamp exam with measurement of intraocular pressure (IOP), and evaluation of cup/disk ratio. RESULTS: A total of 2560 individuals were screened; the mean age was 59 +/- 13 years. IOP > or = 21 mmHg was found in 4.8%, and 12.3% had cupping > or = 0.5. IOP > or = 21 mmHg together with cupping > or = 0.5 were present in 1.4% and this rate increased with age: 3.7% of cases in the age group > or = 70 years compared to 1% and 0.6% in the age groups 50-69 and < 50 years, respectively (P < 0.001). Likewise, the prevalence of cupping > or = 0.7 and of IOP > or = 24 mmHg increased significantly with age. The prevalence of IOP > or = 21 mmHg increased in cases with a family history of glaucoma in first-degree relatives (10.5% compared to 3.9%, P < 0.001). The prevalence of IOP > or = 21 mmHg was also increased in diabetic patients (8.3% vs. 4.3% in non-diabetics, P = 0.002). Further ophthalmologic evaluation was recommended to 13% of the screened individuals. CONCLUSIONS: Outreach screening for glaucoma is a valuable tool for detecting glaucoma, pre-perimetric glaucoma, or ocular hypertension in a meaningful number of previously undiagnosed cases. Yet, cost-effectiveness issues should also be considered. The yield of such screening increases with age and seems to be most advantageous in cases with diabetes or a family history of glaucoma.

Tonopen XL assessment of intraocular pressure through silicone hydrogel contact lenses.

OBJECTIVES: To assess the accuracy of Tonopen XL measurement of intraocular pressure (IOP) through low-power (-0.25 to -3.00) and high power (-3.25 to -6.00) silicone hydrogel lenses of 3 different materials (galyfilcon A, senofilcon A, and lotrafilcon B). METHODS: Seventy-eight patients were recruited for participation in this study. All were habitual wearers of silicone hydrogel contact lenses, and none had been diagnosed with glaucoma, ocular hypertension, or anterior surface disease. IOP was measured with and without lenses in place in the right eye only. Patients were randomized to initial measurement either with or without the lens in place. A single examiner collected all data. RESULTS: No statistically significant differences were noted between IOP measured without lenses and IOP measured through low-power lotrafilcon B lenses or high-power or low-power galyfilcon A and senofilcon A lenses. However, we did find a statistically significant difference between IOP measured without lenses and IOP measured through high-power lotrafilcon B lenses. CONCLUSION: In general, Tonopen XL measurement of IOP through silicone hydrogel lenses may be sufficiently accurate for clinical purposes. However, Tonopen XL may overestimate IOP if performed through a silicone hydrogel lens of relatively high modulus.

Intraocular pressure assessment after laser in situ keratomileusis: a review.

This paper aims to review the current methods available for the measurement of intraocular pressure after myopic laser in situ keratomileusis for the correction of myopia. Searches were performed for studies that assessed or compared various methods of intraocular pressure assessment. There were 20 eligible studies that explored the use of pneumotonometry, pressure phosphene tonometry, rebound tonometry, dynamic contour tonometry, statistical modeling, mathematical formulae, ocular response analyzer and even measuring intraocular pressure on the nasal cornea. Our review shows that an ideal method would be one that is independent of corneal factors. Dynamic contour tonometry and pressure phosphene tonometry held promise in research settings. More studies need to be done to validate the new methods of intraocular pressure assessment, especially in glaucoma patients. It is important to empower laser in situ keratomileusis patients with knowledge of these difficulties and potential implications for the future.

Assessment of a new Goldmann applanation tonometer.

BACKGROUND/AIMS: The classic Goldmann applanation tonometer (GAT) has been further developed by Haag-Streit International. The applanation principle has been retained, while the internal force transmission and the pressure gauging have been optimised, the display of results digitised. The authors compared the GAT standard with the new GAT digital. METHODS: Four fixed tonometer pairs were used. The protocol included: non-contact pachymetry, slit-lamp examination, three consecutive measurements with each tonometer with a 5 min interval in between, check for side effects in 15 min. Three groups (intraocular pressure (IOP) levels) were defined: (1) IOP ≤ 16; (2) IOP>16 and <23; (3) IOP ≥ 23 mm Hg. RESULTS: 125 Patients (250 eyes) were evaluated. IOP (mm Hg), GAT standard versus GAT digital, for the rights eyes was: Group 1: 12.94 ± 0.55 versus 13.11 ± 0.53, p=0.71. Group 2: 18.26 ± 0.59 versus 18.03 ± 0.52, p=0.53; Group 3: 30.28 ± 0.48 versus 30.42 ± 0.41, p=0.97; all right eyes: 17.48 ± 7.48 versus 17.73 ± 7.4, p=0.99. For the left eyes, there was no significant difference, either. The correlation was very good and was not influenced by the IOP level. The Pearson coefficient for the right eye was 0.985, and for the left eye 0.994. In the Bland-Altman analysis, although there were two single readings that differed by as much as 5 mm Hg, GAT digital measures showed almost no skew, and the mean difference was 0.03 ± 1.23 mm Hg (n=250). A multiple regression analysis showed no influence of order of measurement, eyeside or pachymetry. CONCLUSIONS: The new GAT digital is as reliable and safe as GAT standard. IOP values correlate well. It offers a digitised display and a wireless transfer of data. The display of values up to the first decimal digit is not necessarily associated with a more precise measurement, but may offer an additional comfort compared with the 2 mm Hg scale of the classic GAT.