Goldmann Tonometry and Corneal Biomechanics

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.

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Differences between Goldmann Applanation Tonometry and Dynamic Contour Tonometry following Trabeculectomy

Journal of Ophthalmology ◽

10.1155/2010/357387 ◽

2010 ◽

Vol 2010 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Efstathios T. Detorakis ◽

Emilia Grammenandi ◽

Ioannis G. Pallikaris ◽

Miltiadis K. Tsilimbaris

Keyword(s):

Mechanical Properties ◽

Central Corneal Thickness ◽

Corneal Thickness ◽

Applanation Tonometry ◽

Goldmann Applanation Tonometry ◽

Dynamic Contour Tonometry ◽

Control Group ◽

Clinical Parameters ◽

History Of ◽

The Difference

Background. To evaluate differences between Goldmann Applanation Tonometry (GAT) and Dynamic Controur Tonometry (DCT) following trabeculectomy.Methods. Thirty eight glaucomatous eyes with a history of trabeculectomy (Trabeculectomy group, TG), 20 eyes without a history of trabeculectomy but with a history of latanoprost use (Latanoprost group, LG), and 19 nonglaucomatous eyes (Control group, CG) were included. GAT-IOP, DCT-IOP, the difference between them (dIOP), the central corneal thickness (CCT), the axial length (AL), and the depth of the anterior chamber (ACD) were measured.Results. dIOP was significantly higher in TG (5.19 mmHg) than in LG (4.01 mmHg) and CG (1.98 mmHg). Correlations between AL and dIOP were statistically significant in both TG and LG but not in CG whereas correlations between dIOP and other clinical parameters examined were statistically not significant in all groups.Conclusions. The significantly higher dIOP in TG implies that the bio-mechanical properties of the ocular walls are altered following trabeculectomy.

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Intraocular Pressure Changes Following Different Keratoplasty Techniques and Association with Cornea Parameters and anterior Chamber Depth

10.21203/rs.3.rs-254015/v1 ◽

2021 ◽

Author(s):

Gülşah Gümüş ◽

cigdem altan ◽

yusuf yildirim ◽

nilay kandemir besek ◽

selim genç ◽

...

Keyword(s):

Intraocular Pressure ◽

Anterior Chamber ◽

Corneal Thickness ◽

Anterior Chamber Depth ◽

Early Postoperative Period ◽

Lamellar Keratoplasty ◽

Deep Anterior Lamellar Keratoplasty ◽

Anterior Lamellar Keratoplasty ◽

The Difference ◽

Pressure Changes

Abstract Purpose To evaluate early intraocular pressure (IOP) changes following different keratoplasty techniques and to investigate the relationship between corneal thickness (CT), keratometry values, anterior chamber depth (ACD) and IOP changes. Methods We included patients who underwent penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK) and Descemet membrane endothelial keratoplasty (DMEK). ACD, CT, and keratometry measurements were repeated postoperatively at hour 24, week 1, and month 1. IOP measurements were repeated at postoperative hours 6 and 24, week 1, and month 1 by Tono-Pen XL. Results Twenty-two patients underwent PK, 12 patients underwent DALK, and 19 patients underwent DMEK. The difference between the IOP preoperatively and 6 hours postoperatively and between the IOP preoperatively and 24 hours postoperatively were statistically significant in the three types of surgery (p < 0.05 for each). The difference between preoperative and postoperative week 1 IOP was statistically significant only in the PK group (p = 0.023). When the IOP was compared between the three types of surgeries, the IOP at postoperative week 1 in the PK group was significantly higher than the DALK and DMEK groups (p = 0.021). There was no correlation between ACD, corneal thickness, K values, and IOP in any group. Conclusion IOP may increase in all types of keratoplasty during the first hours after surgery, but PK has a risk of high IOP longer in the early postoperative period. PK patients should be followed more carefully during postoperative week 1 to check for an increase in IOP.

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Therapeutic effectiveness of frozen platelet concentrates for transfusion

Blood ◽

10.1182/blood.v57.2.243.243 ◽

1981 ◽

Vol 57 (2) ◽

pp. 243-249 ◽

Cited By ~ 28

Author(s):

HM Lazarus ◽

EA Kaniecki-Green ◽

SE Warm ◽

M Aikawa ◽

RH Herzig

Keyword(s):

Vapor Phase ◽

Platelet Concentrate ◽

In Vitro Tests ◽

Platelet Concentrates ◽

Emergency Situations ◽

Ultrastructural Studies ◽

Significant Difference ◽

Before And After ◽

The Difference

Abstract Six patients received platelet concentrate transfusions from their HLA- identical siblings. Platelet concentrates were administered either fresh, or after being frozen in 10% dimethylsulfoxide, at a slow controlled rate (1 degree C/min) or rapidly (approximately 8 degrees C/min) in the vapor-phase of a liquid nitrogen refrigerator. The median freeze-thaw loss was 13.5%. The mean 1-hr and 20-hr corrected increments in platelet count were calculated for fresh platelet concentrates transfused before and after transfusion with controlled- rate frozen and vapor-phase frozen platelet concentrates. There was no significant difference among the first and second transfusion of fresh platelet concentrates, nor was the difference observed between fresh and controlled-rate frozen platelet concentrates significant. The difference between fresh and vapor-phase frozen platelet concentrates, and between controlled-rate frozen and vapor-phase frozen platelet concentrates were highly significant (p < 0.01). In vitro tests of aggregation using ristocetin and platelet ultrastructural studies paralleled the transfusion experience. Our results indicate that HLA- identical platelet concentrates can be successfully frozen and thawed for transfusion if a slow, controlled rate of freezing is employed. The use of HLA-identical frozen platelet concentrates may be important in emergency situations for the refractory patient and potentially for the establishment of a platelet concentrate bank.

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Contribution of intermediate filaments to cell stiffness, stiffening, and growth

AJP Cell Physiology ◽

10.1152/ajpcell.2000.279.1.c188 ◽

2000 ◽

Vol 279 (1) ◽

pp. C188-C194 ◽

Cited By ~ 195

Author(s):

Ning Wang ◽

Dimitrije Stamenović

Keyword(s):

Mechanical Properties ◽

Applied Stress ◽

Extended Period ◽

Direct Consequence ◽

Cell Stiffness ◽

Cell Integrity ◽

Wild Type ◽

The Difference ◽

High Degree

It has been shown previously that intermediate filament (IF) gels in vitro exhibit stiffening at high-applied stress, and it was suggested that this stiffening property of IFs might be important for maintaining cell integrity at large deformations (Janmey PA, Evtenever V, Traub P, and Schliwa M, J Cell Biol 113: 155–160, 1991). In this study, the contribution of IFs to cell mechanical behavior was investigated by measuring cell stiffness in response to applied stress in adherent wild-type and vimentin-deficient fibroblasts using magnetic twisting cytometry. It was found that vimentin-deficient cells were less stiff and exhibited less stiffening than wild-type cells, except at the lowest applied stress (10 dyn/cm2) where the difference in the stiffness was not significant. Similar results were obtained from measurements on wild-type fibroblasts and endothelial cells after vimentin IFs were disrupted by acrylamide. If, however, cells were plated over an extended period of time (16 h), they exhibited a significantly greater stiffness before than after acrylamide, even at the lowest applied stress. A possible reason could be that the initially slack IFs became fully extended due to a high degree of cell spreading and thus contributed to the transmission of mechanical stress across the cell. Taken together, these findings were consistent with the notion that IFs play important roles in the mechanical properties of the cell during large deformation. The experimental data also showed that depleting or disrupting IFs reduced, but did not entirely abolish, cell stiffening. This residual stiffening might be attributed to the effect of geometrical realignment of cytoskeletal filaments in the direction of applied load. It was also found that vimentin-deficient cells exhibited a slower rate of proliferation and DNA synthesis than wild-type cells. This could be a direct consequence of the absence of the intracellular IFs that may be necessary for efficient mediation of mechanical signals within the cell. Taken together, results of this study suggest that IFs play important roles in the mechanical properties of cells and in cell growth.

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Role of pH on stability and mechanical properties of gelatin films

Journal of Bioactive and Compatible Polymers ◽

10.1177/0883911511431484 ◽

2012 ◽

Vol 27 (1) ◽

pp. 67-77 ◽

Cited By ~ 41

Author(s):

Michela Gioffrè ◽

Paola Torricelli ◽

Silvia Panzavolta ◽

Katia Rubini ◽

Adriana Bigi

Keyword(s):

Mechanical Properties ◽

Young’S Modulus ◽

Triple Helix ◽

Young's Modulus ◽

In Vitro Tests ◽

Diffraction Reflection ◽

X Ray Diffraction ◽

Solution Ph ◽

Gelatin Films

The effect of the film-forming solution pH on the triple-helix content, thermal stability, and mechanical properties of gelatin films was investigated. The films were prepared from solutions at different pHs of type A pigskin gelatin, and their mechanical characteristics were determined. At pHs higher than 9 and lower than 5, Young’s modulus, E, and the stress at break, σb, of the films decreased significantly. Cross-linking with genipin reduced deformation at break, ϵb, and increased Young’s modulus. The intensity of the 1.1-nm X-ray diffraction reflection and the denaturation enthalpy decreased at these pHs, indicating that the triple helix reduced. Preliminary in vitro tests on the cross-linked samples indicated good cell proliferation and viability.

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Differential myoblast and tenoblast affinity to collagen, fibrin and mixed threads in the prospect of muscle-tendon junction modelisation

10.1101/2020.05.12.091868 ◽

2020 ◽

Cited By ~ 1

Author(s):

Clément Rieu ◽

Nicolas Rose ◽

Anissa Taleb ◽

Gervaise Mosser ◽

Bernard Haye ◽

...

Keyword(s):

Mechanical Properties ◽

High Amplitude ◽

Myotendinous Junction ◽

Weak Point ◽

High Adherence ◽

Substrate Curvature ◽

The Difference

AbstractThe myotendinous junction transfers forces from muscle to tendon. As such, it must hold two tissues of completely different biological and cellular compositions as well as mechanical properties (kPa-MPa to MPa-GPa) and is subject to frequent stresses of high amplitude. This region remains a weak point of the muscle-tendon unit and is involved in frequent injuries. We here produce fibrin (40 mg/mL, E0 =0.10 ± 0.02 MPa) and collagen (60 mg/mL, E0=0.57 ± 0.05 MPa) threads as well as mixed collagen:fibrin threads (3:2 in mass, E0 = 0.33 ± 0.05 MPa) and investigate the difference of affinity between primary murine myoblasts and tenoblasts. We demonstrate a similar behavior of cells on mixed and fibrin threads with high adherence of tenoblasts and myoblasts, in comparison to collagen threads that promote high adherence and proliferation of tenoblasts but not of myoblasts. Besides, we show that myoblasts on threads differentiate but do not fuse, on the contrary to 2D control substrates, raising the question of the effect of substrate curvature on the ability of myoblasts to fuse in vitro.

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On the difference in heel pad mechanics as deduced from in vivo and in vitro tests

Journal of Biomechanics ◽

10.1016/0021-9290(94)91198-3 ◽

1994 ◽

Vol 27 (6) ◽

pp. 751

Author(s):

P. Aerts ◽

R.F. Ker ◽

D. De Clercq ◽

R.McN. Alexander

Keyword(s):

In Vitro Tests ◽

Heel Pad ◽

The Difference

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Endothelial Cell Loss after Phacoemulsification according to Different Anterior Chamber Depths

Journal of Ophthalmology ◽

10.1155/2015/210716 ◽

2015 ◽

Vol 2015 ◽

pp. 1-7 ◽

Cited By ~ 10

Author(s):

Hyung Bin Hwang ◽

Byul Lyu ◽

Hye Bin Yim ◽

Na Young Lee

Keyword(s):

Endothelial Cell ◽

Anterior Chamber ◽

Corneal Thickness ◽

Cell Loss ◽

Dissipated Energy ◽

Corneal Endothelial Cells ◽

Endothelial Cell Loss ◽

Cumulative Dissipated Energy ◽

The Difference ◽

A Prospective Study

Purpose. To compare the loss of corneal endothelial cells after phacoemulsification according to different anterior chamber depths (ACDs).Methods. We conducted a prospective study on 135 eyes with senile cataracts. Eyes with nuclear density grades of 2 to 4 were divided into three groups according to ACD: ACD I, 1.5 < ACD ≤ 2.5 mm; ACD II, 2.5 < ACD ≤ 3.5 mm; or ACD III, 3.5 < ACD ≤ 4.5 mm. Intraoperative mean cumulative dissipated energy (CDE) was measured. Clinical examinations included central corneal thickness (CCT) and endothelial cell count (ECC) preoperatively and 2 months postoperatively.Results. There were no significant differences in CDE among the ACD groups (P>0.05). Endothelial cell loss was significantly higher in ACD I than in ACD III in grades 3 and 4 cataract density groups 2 months after phacoemulsification (P<0.05). There were also more changes in CCT in all of the cataract density groups in the ACD I group compared to the ACD II and III groups 2 months postoperatively, but the difference was not statistically significant.Conclusions. Eyes with shallow ACDs, especially those with relatively hard cataract densities, can be vulnerable to more corneal endothelial cell loss in phacoemulsification surgery.

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Study of the deformation of sponge application hemostatic materials

Research n Practical Medicine Journal ◽

10.17709/2409-2231-2020-7-3-2 ◽

2020 ◽

Vol 7 (3) ◽

pp. 21-32

Author(s):

V. A. Lipatov ◽

D. A. Severinov ◽

M.D. Z. Naimzda ◽

E. L. Puchkova

Keyword(s):

Mechanical Properties ◽

Residual Strain ◽

Glass Substrate ◽

Residual Deformation ◽

Lower Surface ◽

Vitro Experiment ◽

In Vitro Experiment ◽

Load Removal ◽

The Difference

Purpose of the study. To evaluate the dynamics of deformation of spongy application hemostatic materials in an in vitro experiment. Materials and methods. As materials of the study the following samples of hemostatic materials were used: Tachocomb (No. 1), Gelita-Spon Standard (No. 2), Reggicel Fibrillar (No. 3), samples of hemostatic sponges developed jointly with Lintex (St.Petersburg, Russia) on the basis of sodium-Carboxymethyl Cellulose (No. 3): Samples were placed on a glass substrate which was mounted on the rising REM cross-arm 0.2–1 to estimate 50% compression residual strain. A glass substrate rigidly attached to the indenter was mounted so that its lower surface would touch the upper surface of the sample. The crossarm was then lifted at 30 mm/min, compressing the sample until the force reached 50 N, after which the sample was allowed to stand under pressure for 10 seconds. After the load was removed, the sample was removed from the substrate and the compression thickness measured (immediately after compression, after 5, 10 and 30 minutes). Results. The values of the compression residual deformation on the thickness 50% (immediately after the load removal) of the samples of group No. 1 differ statistically significantly from the values of groups No. 2 and No. 3 on 5.92 and 3.51, respectively. The difference between groups No. 1 and No. 4 is 5.61. The ODP values 50% 5 minutes after the load of Group No. 1 samples was removed differ from Groups No. 2 and No. 3 on 5.93 and 3.85, respectively. The difference between groups No. 1 and No. 4 is 6.57. After 30 minutes after compression, the values of the residual deformation of the samples of group No. 1 differ from those of groups No. 2 and No. 3 on 6.9 and 4.3. The difference between groups No. 1 and No. 4 is 6.9. Also, the values of the residual deformation of the samples of group No. 2 exceed the values of the samples of group No. 3 by 1.6 times, and in comparison with group No. 4 is less by 0.03. There are fewer statistical differences with other groups in pilot groups 5–7. Conclusion. The highest values of the indicator "residual deformation at compression by thickness 50%" are noted in group No. 7 (samples based on Na-CMC unpressurized) — 32.34, which causes high mechanical properties of jaws made from this material.

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