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 The influence of corneal density and thickness on tonometry measurement with goldmann applanation, non-contact and iCare tonometry methods

2022 ◽  
Author(s):  
Ahmed Lubbad ◽  
Irene Oluwatoba-Popoola ◽  
Melanie Haar ◽  
Carsten Framme ◽  
Anna Bajor
Keyword(s):  
Linear Regression Analysis ◽  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Multiple Linear Regression Analysis ◽  
Influential Factors ◽  
Total Density ◽  
Camera System ◽  
System Data ◽  
The Mean ◽  
Mean Differences

Abstract Purpose To evaluate the effect of corneal density and thickness on the accuracy of tonometry readings obtained via three most used techniques. Method Intraocular pressures of 45 patients’ right eyes were measured using Goldmann Applanation, iCare, and non-contact tonometry methods. Corneal parameters were obtained using the Pentacam Camera System. Data obtained were analyzed using Paired t Test, Pearson’s correlation coefficient, multiple linear regression analysis, and Bland–Altman plots. Results The mean corneal thickness was 545.4 ± 3.93 μm. The mean corneal density of total, stromal, 0–2 mm, and 2–6 mm zones were 27.85 ± 6.23 GSU, 24.61 ± 6.05 GSU, 20.76 ± 2.96 GSU, and 20.81 ± 3.51 GSU respectively. IOP readings had a statistically significant correlation with corneal stromal thickness, as well as with total and stromal density. The stromal density, however, showed higher correlation with the three tonometry methods than did the total density (iCare:  − .482 (0.001) stromal density versus− .464 (0.001) total density, NCT: − .376 (0.011) versus − .353 (0.017), GAT: − .306 (0.041) versus − .296 (0.048)). Statistical differences were found in comparing the iCare readings with GAT (P < 0,00) and with NCT (P < 0,00), with mean differences of 1.8 mmHg ± 2.6 and 2.0 mmHg ± 2.6 respectively. GAT and NCT measurements showed no statistical difference (P > 0.05). Conclusion This study shows that both central corneal thickness and stromal density are significant influential factors of reliable IOP readings. It is necessary to consider more corneal biomechanical properties, as well as exercise a high degree of caution in any new attempts towards adjusting an IOP-correction equation.

Relationship between novel intraocular pressure measurement from Corvis ST and central corneal thickness and corneal hysteresis

2019 ◽  
Vol 104 (4) ◽  
pp. 563-568 ◽  
Author(s):  
Masato Matsuura ◽  
Hiroshi Murata ◽  
Yuri Fujino ◽  
Mieko Yanagisawa ◽  
Yoshitaka Nakao ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Central Corneal Thickness ◽  
Linear Regression Analysis ◽  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Applanation Tonometry ◽  
Corneal Hysteresis ◽  
Corneal Resistance Factor ◽  
Corvis St ◽  
The Relationship

AimsCorvis ST (CST) yields biomechanical corrected IOP (bIOP) which is purported to be less dependent on biomechanical properties. In our accompanied paper, it was suggested that the repeatability of bIOP is high. The purpose of the current study was to assess the relationship between intraocular pressure (IOP) measured with CST and central corneal thickness (CCT) and corneal hysteresis (CH), in comparison with IOP measured with Goldmann applanation tonometry (GAT) and the ocular response analyzer (ORA).MethodsA total of 141 eyes from 141 subjects (35 healthy eyes and 106 glaucomatous eyes) underwent IOP measurements with GAT, CST and ORA. The relationships between IOP measurements (ORA-IOPg, ORA-IOPcc, CST-bIOP and GAT IOP) and biomechanical properties (CCT, CH and corneal resistance factor (CRF)) were analysed using the linear regression analysis.ResultsIOPg, IOPcc and GAT IOP were significantly associated with CCT (p<0.001), whereas bIOP was not significantly associated with CCT (p=0.19). IOPg, bIOP and GAT IOP were significantly associated with CH (IOPg: p<0.001; bIOP: p<0.001; GAT IOP: p=0.0054), whereas IOPcc was not significantly associated with CH (p=0.18). All of IOP records were associated with CRF (p<0.001).ConclusionThe bIOP measurement from CST is independent from CCT, but dependent on CH and CRF.

scholarly journals Structural and Biomechanical Corneal Differences between Type 2 Diabetic and Nondiabetic Patients

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
João N. Beato ◽  
João Esteves-Leandro ◽  
David Reis ◽  
Manuel Falcão ◽  
Vítor Rosas ◽  
...  
Keyword(s):  
Linear Regression ◽  
Linear Regression Analysis ◽  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Cross Sectional Study ◽  
Applanation Tonometry ◽  
Multivariate Linear Regression ◽  
Multivariate Linear Regression Analysis ◽  
Cross Sectional

Purpose. To analyze and compare corneal structural and biomechanical properties, characterized by corneal hysteresis (CH) and resistance factor (CRF), between patients with and without type 2 diabetes mellitus (DM), and determine the main ocular variables that influence them. Methods. Sixty diabetic and 48 age- and sex-matched non-DM patients were enrolled in this cross-sectional study. The DM group was analyzed according to DM duration (<or ≥ 10 years), HbA1c levels (<or ≥ 7%), and presence of retinopathy. CH and CRF were evaluated using the Ocular Response Analyzer® (ORA). Central corneal thickness (CCT) was determined by Scheimpflug tomography (Pentacam® HR). Intraocular pressure was obtained with ORA (IOPcc) and Goldmann applanation tonometry (IOP-GAT). Univariate and multivariate linear regression analyses were performed to evaluate the relationship between demographical, clinical, and ocular variables with the biomechanical properties. Results. There were no statistically significant differences in the CH and the CRF between DM and non-DM groups (p=0.637 and p=0.439, respectively). Also, there was no statistical difference between groups for the CCT, IOPcc, or IOP-GAT. Multivariate linear regression analysis showed that CH was positively associated with CCT (p<0.001) and negatively associated with IOPcc (p<0.001), while CRF was positively associated with CCT (p<0.001) and IOPcc (p=0.014). Conclusion. The CCT and IOPcc were found to be the main parameters that affect corneal biomechanical properties both in diabetics and controls. In this study, there was no significant effect of DM type 2 on corneal biomechanics.

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.

Single-position calibration of the respiratory inductance plethysmograph

1983 ◽  
Vol 55 (3) ◽  
pp. 1031-1034 ◽  
Author(s):  
B. Loveridge ◽  
P. West ◽  
N. R. Anthonisen ◽  
M. H. Kryger
Keyword(s):  
Body Position ◽  
Linear Regression Analysis ◽  
Correlation Coefficients ◽  
Normal Subjects ◽  
Calibration Method ◽  
Calibration Procedure ◽  
Multiple Linear Regression Analysis ◽  
Breathing Patterns ◽  
Calibration And Verification ◽  
The Stability

Since we intended to use the respiratory inductance plethysmograph (RIP) to study breathing patterns in a single body position, we developed a method to calibrate the RIP in one position (seated) and verified the stability of this calibration procedure during a 60-min period. The subject breathed spontaneously through a pneumotachograph for 1 min during all calibration and verification runs. All inspiratory data from the abdomen and rib cage RIP transducers was analyzed using multiple linear regression analysis to calculate calibration factors for the transducers. Eight normal subjects were studied, and the stability of calibration at 20, 40, and 60 min was determined. The correlation coefficients were all greater than 0.94. The mean slope and mean intercept describing the relationship of the RIP volume to the pneumotachograph volume for all calibration and verification runs were 0.995 +/- 0.074 and 0.012 +/- 0.018 liter, respectively. This calibration method allows a spirogram to be generated from the RIP signals. Therefore, this technique may be valuable in further investigating resting breathing patterns in humans.

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 Corneal Parameters in Healthy Subjects Assessed by Corvis ST

2020 ◽  
Author(s):  
Ramin Salouti ◽  
Mansoureh Bagheri ◽  
Anis Shamsi ◽  
Mohammad Zamani ◽  
Maryam Ghoreyshi ◽  
...  
Keyword(s):  
Linear Regression Analysis ◽  
Corneal Thickness ◽  
Case Series ◽  
Biomechanical Properties ◽  
Radius Of Curvature ◽  
Corvis St ◽  
Deformation Amplitude ◽  
Study Results ◽  
The Mean ◽  
The Right

Purpose: To evaluate corneal biomechanics using Corvis ST in healthy eyes from Iranian keratorefractive surgery candidates. Methods: In this prospective consecutive observational case series, the intraocular pressure (IOP), central corneal thickness (CCT), and biomechanical properties of 1,304 eyes from 652 patients were evaluated using Corvis ST. Keratometric readings and manifest refraction were also recorded. Results: The mean (±SD) age of participants was 28 ± 5 years, and 31.7% were male. The mean spherical equivalent refraction was –3.50 ± 1.57 diopters (D), the mean IOP was 16.8 ± 2.9 mmHg, and the mean CCT was 531 ± 31 μm for the right eye. The respective means (±SD) corneal biomechanical parameters of the right eye were as follows: first applanation time: 7.36 ± 0.39 milliseconds (ms); first applanation length: 1.82 ± 0.22 mm; velocity in: 0.12 ± 0.04 m/s; second applanation time: 20.13 ± 0.48 ms; second applanation length: 1.34 ± 0.55 mm; velocity out: –0.67 ± 0.17 m/s; total time: 16.84 ± 0.64 ms; deformation amplitude: 1.05 ± 0.10 mm; peak distance: 4.60 ± 1.01 mm; and concave radius of curvature: 7.35 ± 1.39 mm. In the linear regression analysis, IOP exhibited a statistically significant association with the first and second applanation times, total time, velocity in, peak distance, deformation amplitude, and concave radius of curvature. Conclusion: Our study results can be used as a reference for the interpretation of Corvis ST parameters in healthy refractive surgery candidates in the Iranian population. Our results confirmed that IOP is a major determinant of Corvis parameters.

scholarly journals IOP change after phacoemulsification with PCIOL implantation and its association with ocular biometric parameters

2021 ◽  
Vol 7 (3) ◽  
pp. 466-470
Author(s):  
Sharah Rahman ◽  
Jalal Ahmed ◽  
Anisur Rahman ◽  
Ishtiaque Anwar ◽  
Tarzia Asma Zafrullah ◽  
...  
Keyword(s):  
Graphical Representation ◽  
Linear Regression Analysis ◽  
Corneal Thickness ◽  
Anterior Chamber Depth ◽  
Posterior Chamber ◽  
Biometric Parameters ◽  
Age Related ◽  
Applanation Tonometer ◽  
The Mean ◽  
The Impact

: To assess the impact on intraocular pressure (IOP) after Phacoemulsification (PE) with Posterior Chamber Intraocular Lens (PCIOL) implantation and its relation with ocular biometric parameters. The study was a prospective observational study included 524 eyes with normal IOP (11-21 mmHg) who underwent uneventful Phacoemulsification with PCIOL Implantation surgery for age-related cataract. IOP, Central Corneal Thickness (CCT), Anterior Chamber Depth (ACD), Axial Length (AL) were measured pre-operatively and one month post-operatively by Goldman Applanation Tonometer, Corneal Pachymeter and Optical Coherence Biometer, respectively. The post-operative IOP change and its relation with preoperative biometric parameters were determined.: The mean pre-operative and post-operative IOP was 13.44±1.98 & 11.54±1.66mmHg, respectively, with an average IOP reduction after one month of 1.90±0.61mmHg. The mean pre-operative and post-operative ACD was 3.27±0.24 and 3.66±0.27 mm, respectively, with an average increase of 0.39 ±0.3 mm. Paired t-test showed post-operative IOP reduction was significantly associated with preoperative IOP (p&#60;0.001) and ACD (p&#60;0.001). But CCT and AL were not significantly associated. The linear regression analysis confirmed the proportional reduction of post-operative IOP, r 0.921. So 92.1% of the preoperative IOP is proportional to post-operative IOP reduction. The graphical representation shows more the pre-operative IOP, more the post-operative IOP reduction.: IOP is significantly reduced, and ACD increased after PE with PCIOL implantation surgery and is associated with post-operative IOP reduction. The post-operative IOP reduction is proportional to pre-operative IOP, and more the preoperative IOP, more the post-operative IOP reduction.

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