Goldmann Tonometry Correction Factors Based on Numerical Analysis

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Ahmed Elsheikh ◽  
Daad Alhasso ◽  
David Pye
Keyword(s):  
Material Properties ◽  
Current Knowledge ◽  
Numerical Study ◽  
Corneal Thickness ◽  
Correction Factors ◽  
Goldmann Tonometry ◽  
Applanation Tonometer ◽  
Iop Measurement ◽  
Natural Variations ◽  
Current Reference Standard

With the world’s aging population, it is expected that the number of people affected by glaucoma, the second most common cause of irreversible blindness, will increase considerably. Current knowledge on glaucoma progression relates elevation of the intraocular pressure (IOP) to optic nerve damage and hence visual impairment. For this reason, IOP measurement in tonometry has become an essential part of routine eye examinations needed for the diagnosis and management of the disease. The accuracy of the current reference standard in tonometry, the Goldmann applanation tonometer, is known to be affected by the natural variations in corneal thickness, curvature, and material properties. Earlier studies attempted to quantify these effects and produced correction factors that considered the variations in each one of these parameters separately, and no guidance was given as to how to combine the effects of variations in more than one parameter. The present research attempted to address this gap by conducting a multidimensional numerical study that considered variations in thickness, curvature, material properties, and IOP, and used the results to develop a single correction equation that considered these parameters simultaneously. The results of the analysis and the correction equation were validated successfully against the outcome of earlier clinical and mathematical studies on the effect of individual parameters, and the correction equation was presented in a simple form suitable for clinical application.

scholarly journals Effect of Hemifacial Spasm on Intraocular Pressure Measurement

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Erdogan Cicik ◽  
Rengin Yildirim ◽  
Ceyhun Arici ◽  
Funda Dikkaya ◽  
Osman Sevki Arslan
Keyword(s):  
Intraocular Pressure ◽  
Healthy Volunteers ◽  
Hemifacial Spasm ◽  
Clinical Decision Making ◽  
Corneal Thickness ◽  
Clinical Decision ◽  
Age And Gender ◽  
Applanation Tonometer ◽  
Iop Measurement ◽  
And Gender

Purpose. To evaluate the effect of hemifacial spasm (HFS) on intraocular pressure (IOP) measurement. Methods. Twenty-four consecutive patients with HFS and 25 age- and gender-matched randomly selected eyes of healthy volunteers underwent corneal pachymetry and IOP measurements using Goldmann applanation tonometer (GAT) and noncontact tonometer (NCT). IOP measurements were performed before (during HFS) and 2 weeks after Botox injections in HFS patients and in healthy volunteers without Botox injections. Results. There was no statistical difference between involved eye side and uninvolved eye side of HFS patients in measured central corneal thickness. Similarly, no difference was found between involved eye side of HFS patients and controls. There were no statistically significant differences comparing IOP values before treatment and levels measured at 2 weeks of Botox injections, either with GAT (p=0.33, 0.11) or NCT (p=0.80, 0.43) devices in the involved eyes and uninvolved eyes of patients with HFS, respectively. There were also no significant differences in these parameters (GAT (p=0.63) and NCT (p=0.54)) in controls. Conclusions. Contractions in facial muscles may not lead to significant increase in IOP in HFS patients. This result may help clinical decision making in the treatment of glaucoma patients with HFS. This trial is registered with NCT03390803.

Comparison of intraocular pressure using Goldmann applanation tonometry versus non-contact tonometry in eyes with high-viscosity silicone oil

2019 ◽  
Vol 30 (3) ◽  
pp. 494-499 ◽  
Author(s):  
Dionysios D Pagoulatos ◽  
Zoi G Kapsala ◽  
Olga E Makri ◽  
Ilias G Georgalas ◽  
Constantinos D Georgakopoulos
Keyword(s):  
Intraocular Pressure ◽  
Silicone Oil ◽  
Corneal Thickness ◽  
Measurement Techniques ◽  
High Viscosity ◽  
Applanation Tonometry ◽  
Applanation Tonometer ◽  
Iop Measurement ◽  
Prospective Comparative Study ◽  
Silicone Oil Tamponade

Background: To compare intraocular pressure (IOP) measurements using Goldmann applanation tonometer (GAT) and air tonometer (non-contact tonometry [NT]) in vitrectomized eyes with high-viscosity silicone oil tamponade, as well as in normal eyes. Patients and Methods: In this prospective comparative study, 32 eyes with silicone oil tamponade of high viscosity (5700 CS) and 32 normal fellow eyes were included. IOP was measured by GAT and air tonometer 30 ± 12 days after vitrectomy, while measurements of central corneal thickness (CCT) were also obtained. Results: In eyes with silicone oil, IOP was 20.09 ± 4.91 mmHg and 16.75 ± 3.86 mmHg using contact tonometer and air tonometer, respectively ( p < 0.0001). In normal eyes, IOP was 16.41 ± 2.15 mmHg and 16.31 ± 2.49 mmHg using the same tonometry techniques and this difference was not statistically significant ( p = 0.598). In addition, no significant correlation was detected between IOP measurements using both techniques and age, gender, CCT, and type of lens. Conclusions: It seems that GAT overestimates IOP in eyes with high-viscosity silicone oil compared with NT, while both IOP measurement techniques in normal eyes provide similar values. Further assessment of available IOP measurement methods could possibly establish the most accurate technique for IOP estimation in vitrectomized eyes with silicone oil tamponade.

Ocular Response Analyzer versus Goldmann Applanation Tonometer for Measurement of Intra-Ocular Pressure

QJM ◽  
2021 ◽  
Vol 114 (Supplement_1) ◽  
Author(s):  
Rim Raafat Fayez ◽  
Mohamed Adel Abdelshafik ◽  
Ahmed Ibrahim Aboulenain ◽  
Momen Mahmoud Hamdi
Keyword(s):  
Corneal Thickness ◽  
Cross Sectional Study ◽  
Applanation Tonometry ◽  
Ocular Response Analyzer ◽  
Cross Sectional ◽  
Goldmann Applanation Tonometer ◽  
Applanation Tonometer ◽  
Iop Measurement ◽  
The Mean ◽  
Method Of Evaluation

Abstract Background Goldmann applanation tonometry (GAT) has been the gold standard for intraocular pressure(IOP) measurement ,since its appearance in clinical practice around 50 years ago.(1) In spite of being almost unchallenged, the last few years have become a sustained search for a new standard method for IOP measurement,. One such recently marketed instrument is the Ocular Response Analyzer (ORA), which able to detect the corneal biomechanics. Aim of the Work is to compare the IOP measurement estimated by Goldmann applanation tonometer to that of ORA and detect the effect of state of refraction, corneal topography and central corneal thickness (CCT) on these measurements. Patients and Methods This cross-sectional study was done from March 2018 to October 2018 on 65 eyes of patients visiting the outpatient clinic. Results The mean GAT IOP was 15.938 ± 6.041 while the mean ORA (IOPcc) and (IOPg) were 19.711 ± 7.59 and 17.242 ± 7.35 mm Hg respectively. There is a strong positive relationship between GAT IOP & ORA IOPg measurement (r = 0.880 – p = &lt;0.001*). Also finding a weak yet significant correlation between IOPg and CCT (r = 0.385, p = 0.001). None of the pressure measurements was affected by refraction or corneal curvature significantly. Conclusion In conclusion, our results suggest that mean IOPs obtained by ORA were significantly higher than that of GAT with different influencing factors that are not completely understood. caution has to be sought when using the ORA, the values obtained ought not to be used interchangeably with the values obtained by 1 GAT, despite the presence of a positive correlation between these values. This underlines the importance of using one and only method of evaluation of the IOP for every patient in successive follow-up visits.

scholarly journals Factors Affecting the Central Corneal Thickness in Nepalese Population

1970 ◽  
Vol 1 (1) ◽  
pp. 7-10 ◽  
Author(s):  
ST Godar ◽  
KR Kaini ◽  
JB Khattri
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Cross Sectional Study ◽  
Medical Sciences ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Intra Ocular Pressure ◽  
Goldmann Tonometry ◽  
Applanation Tonometer ◽  
Ocular Pressure

Background: Intra Ocular Pressure (IOP) is an important parameter for the detection and monitoring of glaucoma. Central corneal thickness (CCT) can influence the IOP estimated with Goldmann tonometry. A thick cornea overestimates the IOP and thin underestimates it. So, decreased CCT may lead to underdiagnosis and undertreatment of glaucoma and increased CCT may lead to overdiagnosis and overtreatment of glaucoma. The aim of the study is to identify the factors affecting the CCT in Nepalese population. Methods: A hospital based cross-sectional study which enrolled 152 subjects from period of January 2009 to May 2010. All subjects underwent ophthalmological examinations. CCT was measured with ultrasonic pachymeter and intraocular pressure was measured with Goldmann applanation tonometer. Results: The mean±SD CCT of right and left eye was 538±32 and 540±30μm respectively. CCT decreased with increasing age. Age and intra ocular pressure was significantly correlated with CCT. There was no significant correlation of gender and ethnicity with CCT. Conclusion: CCT decreased with increasing age. CCT was significantly correlated with age and intra ocular pressure but not with gender and ethnicity. Keywords: Nepalese; central corneal thickness; ultrasound pachymeter DOI: http://dx.doi.org/10.3126/njms.v1i1.5788   Nepal Journal of Medical Sciences. 2012; 1(1): 7-10.

scholarly journals Changes in corneal properties and its effect on intraocular pressure measurement following phacoemulsification with intraocular lens implantation with or without trabeculectomy

2018 ◽  
Vol 16 (1) ◽  
pp. 35-50
Author(s):  
Ashim Dey ◽  
RathiniLilian David ◽  
Rashima Asokan ◽  
Ronnie George
Keyword(s):  
Intraocular Lens ◽  
Linear Regression Analysis ◽  
Corneal Thickness ◽  
Normal Subjects ◽  
Biomechanical Properties ◽  
Multiple Linear Regression Analysis ◽  
Iol Implantation ◽  
Postoperative Changes ◽  
Applanation Tonometer ◽  
Iop Measurement

Purpose: To evaluate the changes incorneal biomechanical properties and their effect on pre and postoperative differences in IOP measurement by each tonometer Design: Observational study. Methods: The study was done in subjects who underwent phacoemulsification with intraocular lens (IOL) implantation (phaco-IOL) and combined phacoemulsification with IOL implantation and trabeculectomy (phaco-trab). IOP was measured by a single trained examiner using rebound tonometer (RBT), Ocular Response Analyzer (ORA), Goldmann applanation tonometer (GAT), dynamic contour tonometer (DCT), and Tono-Pen. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using ORA, central corneal thickness (CCT) using ultrasonic pachymeter, and corneal curvature (CR) with manual keratometry. All measurements were done one week prior to surgery and after four weeks and six weeks of the two surgeries, respectively. Only the operated eye was included for analysis. Results: Twenty-nine eyes of 29 normal subjects who underwent phaco-IOL and 23 eyes of 23 glaucoma subjects who underwent phaco-trab were studied. Increase in CCT [10.2 ± 14.86 microns, p = 0.001], decrease in CH [0.82 ± 1.38 mmHg, p = 0.003] and CRF [0.97 ± 1.0 mmHg, p < 0.001] were found post-phaco-IOL, whereas post-phaco-trab decrease in CCT [16.61 ± 15.22 microns, p < 0.001], CRF [2.28 ± 1.93 mmHg, p < 0.001] with increase in CH [0.95 ± 1.89 mmHg, p = 0.03] were noted. Multiple linear regression analysis showed significant associations for change in CH and CRF with change in IOP and not with CCT and CR postoperatively. Conclusion: Alterations in CH and CRF were associated with changes in IOP measured postoperatively by different tonometers. CH and CRF changes contribute to postoperative changes in measured IOP.  

scholarly journals Intraocular pressure and choroidal thickness postural changes in multiple system atrophy and Parkinson’s disease

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maddalena De Bernardo ◽  
Giulio Salerno ◽  
Marco Gioia ◽  
Luigi Capasso ◽  
Maria Claudia Russillo ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Intraocular Pressure ◽  
Multiple System Atrophy ◽  
Choroidal Thickness ◽  
Corneal Thickness ◽  
Standing Position ◽  
Sitting Position ◽  
Postural Changes ◽  
Iop Measurement

AbstractTo evaluate intraocular pressure (IOP) and choroidal thickness (ChT) postural changes in multiple system atrophy (MSA), Parkinson’s disease (PD) patients and healthy controls (HC). 20 MSA patients, 21 PD patients and 14 HC, were examined. All subjects underwent a complete examination, including corneal thickness, ChT, IOP and axial length (AL) measurements. IOP measurement was performed in supine, sitting, and standing positions, whereas ChT in sitting and standing positions. Supine to standing IOP variations were significantly higher in MSA vs PD(p = 0.01) and in MSA vs HC (p < 0.0001), whereas no significant differences were observed between PD and HC (p = 0.397). Mean sub-foveal ChT in MSA was 240 ± 92 μm in sitting position, and 215 ± 94 μm in standing position with a significant reduction (p = 0.008). Mean sub-foveal ChT in PD was 258 ± 79 μm in sitting position, and 259 ± 76 μm in standing position (p = 0.887). In HC it was 244 ± 36 μm in sitting position, and 256 ± 37 μm in standing position with a significant increase (p = 0.007). The significant IOP and ChT postural changes can be considered additional hallmarks of autonomic dysfunction in MSA and further studies are needed to consider them as biomarkers in the differential diagnosis with PD.

scholarly journals Goldmann Tonometry and Corneal Biomechanics

2021 ◽  
Vol 11 (9) ◽  
pp. 4025
Author(s):  
Dario Messenio ◽  
Marco Ferroni ◽  
Federica Boschetti
Keyword(s):  
Mechanical Properties ◽  
Anterior Chamber ◽  
Pressure Transducer ◽  
Pearson Correlation ◽  
Corneal Thickness ◽  
Applanation Tonometry ◽  
In Vitro Tests ◽  
Goldmann Tonometry ◽  
The Difference

Glaucoma is the second cause of irreversible blindness in the world. Intraocular pressure (IOP) is a recognized major risk factor for the development and progression of glaucomatous damage. Goldmann applanation tonometry (GAT) is internationally accepted as the gold standard for the measurement of IOP. The purpose of this study was to search for correlations between Goldmann tonometry and corneal mechanical properties and thickness by means of in vitro tests. IOP was measured by the Goldmann applanation tonometer (GIOP), and by a pressure transducer inserted in the anterior chamber of the eye (TIOP), at increasing pressure levels by addition of saline solution in the anterior chamber of enucleated pig eyes (n = 49). Mechanical properties were also determined by inflation tests. The GAT underestimated the real measurements made by the pressure transducer, with most common differences in the range 15–28 mmHg. The difference between the two instruments, highlighted by the Bland–Altman test, was confirmed by ANOVA, normality tests, and Mann–Whitney’s tests, both on the data arranged for infusions and for the data organized by pressure ranges. Pearson correlation tests revealed a negative correlation between (TIOP-GIOP) and both corneal stiffness and corneal thickness. In conclusion, data obtained showed a discrepancy between GIOP and TIOP more evident for softer and thinner corneas, that is very important for glaucoma detection.

scholarly journals ABA Metabolism and Homeostasis in Seed Dormancy and Germination

2021 ◽  
Vol 22 (10) ◽  
pp. 5069
Author(s):  
Naoto Sano ◽  
Annie Marion-Poll
Keyword(s):  
Seed Dormancy ◽  
Current Knowledge ◽  
Fine Tuning ◽  
Environmental Signals ◽  
Hormone Synthesis ◽  
Control Seed ◽  
Functional Relationships ◽  
Aba Metabolism ◽  
Natural Variations ◽  
Germinating Seeds

Abscisic acid (ABA) is a key hormone that promotes dormancy during seed development on the mother plant and after seed dispersal participates in the control of dormancy release and germination in response to environmental signals. The modulation of ABA endogenous levels is largely achieved by fine-tuning, in the different seed tissues, hormone synthesis by cleavage of carotenoid precursors and inactivation by 8′-hydroxylation. In this review, we provide an overview of the current knowledge on ABA metabolism in developing and germinating seeds; notably, how environmental signals such as light, temperature and nitrate control seed dormancy through the adjustment of hormone levels. A number of regulatory factors have been recently identified which functional relationships with major transcription factors, such as ABA INSENSITIVE3 (ABI3), ABI4 and ABI5, have an essential role in the control of seed ABA levels. The increasing importance of epigenetic mechanisms in the regulation of ABA metabolism gene expression is also described. In the last section, we give an overview of natural variations of ABA metabolism genes and their effects on seed germination, which could be useful both in future studies to better understand the regulation of ABA metabolism and to identify candidates as breeding materials for improving germination properties.

scholarly journals Nanomaterials Application in Orthodontics

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 337
Author(s):  
Wojciech Zakrzewski ◽  
Maciej Dobrzynski ◽  
Wojciech Dobrzynski ◽  
Anna Zawadzka-Knefel ◽  
Mateusz Janecki ◽  
...  
Keyword(s):  
Friction Force ◽  
Material Properties ◽  
Orthodontic Treatment ◽  
Mechanical Characteristics ◽  
Current Knowledge ◽  
Scientific Work ◽  
Orthodontic Appliances ◽  
Orthodontic Movement ◽  
Enamel Demineralization

Nanotechnology has gained importance in recent years due to its ability to enhance material properties, including antimicrobial characteristics. Nanotechnology is applicable in various aspects of orthodontics. This scientific work focuses on the concept of nanotechnology and its applications in the field of orthodontics, including, among others, enhancement of antimicrobial characteristics of orthodontic resins, leading to reduction of enamel demineralization or control of friction force during orthodontic movement. The latter one enables effective orthodontic treatment while using less force. Emphasis is put on antimicrobial and mechanical characteristics of nanomaterials during orthodontic treatment. The manuscript sums up the current knowledge about nanomaterials’ influence on orthodontic appliances.

scholarly journals Comparison of IOP Measurement by Goldmann Applanation Tonometer, ICare Rebound Tonometer, and Tono-Pen in Keratoconus Patients after MyoRing Implantation

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Mahmoud Rateb ◽  
Mahmoud Abdel-Radi ◽  
Zeiad Eldaly ◽  
Mohamed Nagy Elmohamady ◽  
Asaad Noor El Din
Keyword(s):  
Central Corneal Thickness ◽  
Pearson Correlation ◽  
Corneal Thickness ◽  
Altman Analysis ◽  
Bland Altman Analysis ◽  
Rebound Tonometer ◽  
Goldmann Applanation Tonometer ◽  
Significant Difference ◽  
Applanation Tonometer ◽  
Icare Rebound Tonometer

Purpose. To evaluate the different IOP readings by Goldmann applanation tonometer (GAT), ICare rebound tonometer, and Tono-Pen in keratoconus patients after MyoRing implantation. To assess the influence of central corneal thickness (CCT) and thinnest corneal location (TCL) on IOP measurements by different tonometers. Setting. Prospective observational study was conducted in two private centers in Egypt from February 2015 to November 2016. Methods. Seventeen eyes of 10 patients suffering from keratoconus and who underwent MyoRing implantation were recruited. All subjects underwent GAT, ICare, and Tono-Pen IOP measurements in random order. Central corneal thickness and thinnest corneal location were assessed by Pentacam. Difference in mean in IOP readings was assessed by T-test. Correlation between each pair of devices was evaluated by Pearson correlation coefficient. The Bland–Altman analysis was used to assess intertonometer agreement. Results. Seventeen eyes (10 patients) were evaluated. The mean IOP reading was 13.9 ± 3.68, 12.41 ± 2.87, and 14.29 ± 1.31 mmHg in GAT, ICare, and Tono-Pen group, respectively. There was a significant difference between IOP readings by GAT/ICare and Tono-Pen/ICare (p value: 0.032 and 0.002, respectively) with no significant difference between GAT/Tono-Pen (p value: 0.554). Mean difference in IOP measurements between GAT/ICare was 1.49 ± 2.61 mmHg, Tono-Pen/ICare was 1.89 ± 2.15 mmHg, and GAT/Tono-Pen was −0.39 ± 2.59 mmHg. There was no significant correlation between the difference in IOP readings among any pair of devices and CCC or TCL. The Bland–Altman analysis showed a reasonable agreement between any pair of tonometers.

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