Corneal Buckling during Applanation and Its Effect on the Air Pressure Curve in Ocular Response Analyzer

Jóźwik, Agnieszka; Kasprzak, Henryk T.; Kozakiewicz, A

doi:10.3390/ijerph16152742

Cited by 3 publications

(7 citation statements)

References 13 publications

(14 reference statements)

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“…The CATS prism has been shown to correct for corneal biomechanical errors in IOP and the difference between CATS and GAT is likely a measure of relative corneal biomechanical properties as demonstrated by its correlation to CCT and CH. 22,23,[26][27][28][29] Similar measures of corneal biomechanical properties such as low CH have been shown to have a significant predictive value for glaucoma progression and higher prevalence in glaucoma patients including NTG patients. 13,16 Similarly, this glaucoma pre-treatment bias suggests there may be higher predictive value for the diagnosis or progression of glaucoma with CATS IOP measurements using historical benchmarks such as 21 mm Hg when compared to GAT prism IOP.…”

Section: Discussionmentioning

confidence: 95%

“…The study findings corroborate well with previous studies and likely validate the effect of corneal stress redistribution and buckling previously discussed. 16,18,19,23,24 CATS tonometer prism IOP measurements have been shown substantially equivalent to flat surfaced GAT prism IOP measurements in patients without disease such as glaucoma and having nominal CCTs between 500 and 600 microns. 26,27 Initial differential CATS minus GAT IOP measurements indicated an average of 1.95 ± 2.23 mm Hg higher IOP with the CATS prism compared to the GAT prism.…”

Section: Discussionmentioning

confidence: 98%

“…15,22 This corneal buckling is supported by other studies. 23,24 The modified CATS prism surface equalizes this pressure distribution across the applanation surface and demonstrates a significantly decreased sensitivity to alterations in the major sources of corneal biomechanical error. 22,[25][26][27][28][29] Decreased non-responder rates were also demonstrated with a modified Goldmann (CATS) prism in patients using the PGA latanoprost and not with timolol use.…”

Section: Discussionmentioning

confidence: 99%

“…There is growing evidence that corneal deformation is affected by a redistributed "buckling stress" and its behavior during applanation is more complex and highly non-linear. [22][23][24] Topical timolol maleate drops have not been shown to have an effect on corneal biomechanical properties. 21 Changes in IOP have been shown to change the cornea's modulus of elasticity and CCT which would affect tonometric IOP accuracy.…”

Section: Introductionmentioning

confidence: 99%

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<p>Improved Efficacy of Topical Latanoprost 0.005% Demonstrated by Corneal Biomechanical Correcting Modified Goldmann Prism</p>

Radcliffe¹,

Berdahl²,

Ibach³

et al. 2020

OPTH

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To evaluate intraocular pressure (IOP) reduction measured by a Goldmann applanation tonometer (GAT) prism and a modified surface Goldmann (CATS) prism with the institution of a topical prostaglandin analog (PGA) or alternatively a topical beta blocker. Design: Prospective, open-label, randomized, controlled, and reference device comparison. Methods: Thirty-six (36) treatment naïve glaucoma patients (72 eyes) were randomized equally to treatment with latanoprost 0.005% or timolol maleate 0.5%. Each patient underwent IOP measurement with standard GAT and CATS prisms before and at 1, 3, and 6 months of treatment. Central corneal thickness (CCT) and corneal hysteresis (CH) were also measured. Medication response was defined as a 20% reduction in IOP from baseline. Results: The CATS prism demonstrated the IOP reduction with topical latanoprost at a mean of 1.9 mmHg lower than the IOP measured with GAT (p=0.01). The CATS and GAT prisms detected no difference in IOP reduction with timolol (p=0.23). The number of latanoprost treatment nonresponders was reduced from 36.1% measured with GAT to 13.8% when measured with the CATS prism (p=0.005). Timolol indicated no difference in the treatment non-response rate at 22.2% (p=0.999). CH increased significantly with latanoprost treatment by an average of 0.55 mmHg (p=0.014) and remained unchanged with timolol at −0.014 mmHg (p=0.68). Discussion: IOP reduction and responder rates were increased when measured with a CATS prism in patients using latanoprost and not with timolol use. Latanoprost-induced alterations in corneal biomechanics may dampen the actual IOP reduction measured with a standard GAT prism. Clinical Trial Registration: ClinicalTrials.gov NCT04178863.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

<p>Improved Efficacy of Topical Latanoprost 0.005% Demonstrated by Corneal Biomechanical Correcting Modified Goldmann Prism</p>

Radcliffe¹,

Berdahl²,

Ibach³

et al. 2020

OPTH

View full text Add to dashboard Cite

show abstract

“…In the paper [ 21 ], both corneal applanations in ORA are examined and the corneal buckling process is described and discussed. It draws attention that the times referring to both bucklings t A and t B are very close to both applanation times t A1 and t A2 , but they are not precisely the same.…”

Section: Introductionmentioning

confidence: 99%

Novel Method of Measuring Corneal Viscoelasticity Using the Corvis ST Tonometer

Boszczyk

Kasprzak

Przeździecka-Dołyk

2022

JCM

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Background: The process of rapid propagation of the corneal deformation in air puff tonometer depends not only on intraocular pressure, but also on the biomechanical properties of the cornea and anterior eye. One of the biomechanical properties of the cornea is viscoelasticity, which is the most visible in its high-speed deformations. It seems reasonable to link the corneal viscoelasticity parameter to two moments of the highest speed of corneal deformations, when the cornea buckles. The aim of this work is to present a method of determining the time and place of occurrence of corneal buckling, examine spatial and temporal dependencies between two corneal applanations and bucklings in the Corvis ST tonometer, and correlate these dependencies with corneal viscoelastic properties. Methods: Images of the horizontal cross section of the Corvis ST deformed cornea from the air puff tonometer Corvis ST were used. 14 volunteers participated in the study, each of them had one eye measured eight times. Mutual changes in the profile slopes of the deformed corneas were numerically determined. They describe pure corneal deformation, eliminating the influence of rotation, and displacement of the entire eyeball. For each point in the central area of the corneal profile, the maximum velocities of mutual slope changes accompanying the applanations were estimated. The times of their occurrence were adopted as buckling times. Results: The propagation of buckling along the corneal profile is presented, as well as the repeatability and mutual correlations between the buckling parameters and intraocular pressure. Based on the relationship between them, a new parameter describing corneal hysteresis: Corvis Viscoelasticity (CVE) is introduced. It is characterized by high repeatability: ICC = 0.82 (0.69–0.93 CI) and low and insignificant correlation with intraocular pressure: r = 0.25 (p-value = 0.38). Conclusion: The results show for the first time how to measure the corneal buckling and viscoelastic effects with Corvis ST. CVE is a new proposed biomechanical parameter related to the viscoelastic properties of the cornea, which has high repeatability for the examined subject. The distribution of its values is planned to be tested on different groups of patients in order to investigate its clinical applicability.

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The method for determining intraocular pressure according to keratotopographic indicators

Ahmetov,

Samoylov,

Usov

2023

jour

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Relevance. In most countries of the world, applanation tonometers remain popular, such as the Maklakov tonometer and the Goldman tonometer. When measuring ophthalmotonus, such tonometers receive IOP values indirectly through the cornea, which certainly introduces its own errors into the measurement results. The creation of methods for measuring IOP different from the currently existing ones is relevant. Purpose: to create a new method for determining intraocular pressure without tonometry, based on the indicators of the individual profi le of the cornea with its parameters, indices and autorefractometry data. Materials and methods. Statistical analysis of 16 parameters of a keratotopograph (ALLEGRO Oculyzer, WaveLight Oculyzer II), data of an autorefractometer (TONOREF Nidek device) and data of tonometric intraocular pressure was carried out using a Maklakov tonometer (НГм2-«ОФТ-П») in 500 patients (1000 eyes). Among the sample population there were patients with both emmetropic refraction – 8 eyes (0.8%), and patients with refractive errors 992 eyes (99.2%), among them: 978 eyes (97.8%) had myopic refraction, 14 (1.4%) eyes had isolated refraction with myopic astigmatism. 889 eyes (88.9%) combined myopic refraction with myopic astigmatism. Results. Based on the analysis of keratotopographic parameters, autorefractometry values and tonometric IOP of 500 patients (1000 eyes), we have created a new method for determining intraocular pressure without tonometry, presented in the form of a mathematical model: Pt keratotopographic = 61.9 – 0.06 × SPH – 2.39 × Rf + 0.64 × Rmin – 0.15 × log2 (IVA) – 31.9 × CKI – 0.006 × Thickness. Conclusions. Based on the results obtained for determining IOP without physical interaction with the eye, the mathematical model created by us can be used in cases where the use of any tonometer is impossible.

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Corneal Buckling during Applanation and Its Effect on the Air Pressure Curve in Ocular Response Analyzer

Cited by 3 publications

References 13 publications

<p>Improved Efficacy of Topical Latanoprost 0.005% Demonstrated by Corneal Biomechanical Correcting Modified Goldmann Prism</p>

<p>Improved Efficacy of Topical Latanoprost 0.005% Demonstrated by Corneal Biomechanical Correcting Modified Goldmann Prism</p>

Novel Method of Measuring Corneal Viscoelasticity Using the Corvis ST Tonometer

The method for determining intraocular pressure according to keratotopographic indicators

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