Does the surface property of a disposable applanation tonometer account for its underestimation of intraocular pressure when compared with the Goldmann tonometer?

Osborne, Sarah F.; Williams, Rachel; Batterbury, Mark; Wong, David

doi:10.1007/s00417-006-0380-9

Cited by 4 publications

(2 citation statements)

References 9 publications

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“…This difference in results between the two instruments has been found to be linked to the corneal resistance factor measured by the Ocular Response Analyzer by Kotecha et al [41], but another possible cause for this IOP measurement difference might be the surface tension developed at the edge of the Goldmann prism when measuring IOP, which should not apply to the PDCT technique. There are published works which suggest that the surface tension of the tear film for the GAT probe might vary from 0.11mmHg [44,45], 0.26mmHg [46] 4.15mmHg [47], 4.67mmHg [48], to 4.7mmHg [49] and hence a difference of 1.9mmHg between the two tonometry techniques could be as a result of surface tension acting during the IOPG measurement.…”

Section: Goldmann Vs Pascal Dct Tonometrymentioning

confidence: 99%

A clinical method for estimating the modulus of elasticity of the human cornea in vivo

Pye

2020

PLoS ONE

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Background To develop a method, using current clinical instrumentation, to estimate the Young's modulus of the human cornea in vivo. Methods Central corneal curvature (CCC), central corneal thickness(CCT), intraocular pressure (IOP) was measured with the Goldmann tonometer (IOPG) and the Pascal Dynamic Corneal Tonometer(PDCT) in one eye of 100 normal young human subjects (21.07 ± 2.94 years) in vivo. The Orssengo and Pye algorithm was used to calculate the Young's modulus of the corneas of these subjects. Results The Young's modulus(E) of the corneas of the subjects using the PDCT and IOPG results (Ecalc) was 0.25 ± 0.10MPa, and without the PDCT results (Eiopg) was 0.29 ± 0.06MPa. The difference in these results is due to the difference in tonometry results between the two instruments, as the mean PDCT result for the subjects was 16.89 ± 2.49mmHg and the IOPG result 15.06 ± 2.71mmHg. E was affected by the CCC of the subjects but more particularly by the CCT and IOP measurements. Corneal stiffness results are also presented. Conclusion Two methods have been developed to estimate the Young's modulus of the human cornea in vivo using current clinical instrumentation. One method (Ecalc) is applicable to the general corneal condition, and Eiopg to the normal cornea, and these results can be used to calculate corneal stiffness.

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Section: Goldmann Vs Pascal Dct Tonometrymentioning

confidence: 99%

A clinical method for estimating the modulus of elasticity of the human cornea in vivo

Pye

2020

PLoS ONE

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“…Es konnte gezeigt werden, dass diese Einwegtonometerköpfchen unabhängig von der absoluten Höhe des IOD etwa 2 mmHg falsch zu niedrige Messergebnisse erbringen [26]. Als Ursache für die-sen unerwarteten systematischen Fehler wird eine weniger hydrophile Oberfläche diskutiert [27].…”

Section: Weiterentwicklungen Der Applanationstonometrie Einwegtonometunclassified

Aktueller Stellenwert der Druckmessung: Messverfahren und Fehlerquellen

Rüfer¹

2016

Klin Monatsbl Augenheilkd

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Tonometry is still an essential component of diagnostic testing in glaucoma. Functional and morphological investigations can provide very detailed information about the extent of glaucomatous damage. They are useful in the early detection of glaucoma damage; when damage is manifest, they are useful in estimating the rate of progression in follow-up studies. In contrast, tonometric procedures are much less perfect and sensitive and provide no information at all about the extent of glaucoma damage. However, they often provide the first evidence that glaucoma may be present at all and they are the decisive parameter in controlling surgical or medical treatment to reduce pressure, as the reduction in intraocular pressure (IOD) is still the most common approach in treating glaucoma - in spite of our awareness of numerous other risk factors for glaucoma. There is no reason to doubt that reducing IOD is an effective therapy in many forms of glaucoma, as this has been demonstrated in numerous large epidemiological studies. Tonometric procedures have become more precise in recent years. Goldmann applanation tonometry (GAT) and pneumatonometry are widely used. There are also some areas for which the rarer forms of tonometry can be recommended. Procedures for quasi-continuous pressure measurements and, in the future, these may replace the current approach of measuring IOD at discrete time points. There are a variety of snares in clinical practice, which may lead to misinterpretation and wrong therapeutic decisions, so that these must be repeatedly emphasised.

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Comparing the Tonojet disposable tonometer with the traditional Goldmann tonometer in glaucomatous and non-glaucomatous eyes

et al. 2013

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Applanation tonometry is widely performed as the most accurate method of measuring intraocular pressure in the clinical setting. Disposable tonometer heads reduce the risk of transmitting infection during applanation and eliminate tonometer head cleaning, which is time-consuming. We performed a study to investigate whether the Tonojet disposable tonometer (Luneau, France) gave comparable intraocular pressure measurements to the standard Goldmann tonometer produced by Haag Streit (Switzerland). The study was performed in a busy general secondary referral ophthalmology clinic in Beaumont Hospital over a 15-day period. We measured intraocular pressure with the Goldmann and Tonojet tonometers in 293 eyes. Patients were randomised as to which tonometer was used first. A diagnosis of glaucoma or ocular hypertension was noted. Central corneal thickness (CCT) was measured. The measurements taken with the Tonojet were on average 2.2 mmHg lower than corresponding measurements taken with the Goldmann applanation tonometer head. The bias was present over the entire range of pressures. The 95 % limits of agreement between the two tonometers ranged from -5.9 to +1.4 mmHg. In the cohort of eyes with ocular hypertension/glaucoma the difference was significantly higher (2.8 vs. 2.1 mmHg). The bias was independent of CCT. We found that the Tonojet disposable tonometer tends to underestimate intraocular pressure compared with the Goldmann. The bias is non-systematic, present over the entire range of pressures and independent of corneal thickness. We conclude that the Tonojet is not sufficiently accurate to constitute a suitable alternative to the Goldmann.

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Does the surface property of a disposable applanation tonometer account for its underestimation of intraocular pressure when compared with the Goldmann tonometer?

Cited by 4 publications

References 9 publications

A clinical method for estimating the modulus of elasticity of the human cornea in vivo

A clinical method for estimating the modulus of elasticity of the human cornea in vivo

Aktueller Stellenwert der Druckmessung: Messverfahren und Fehlerquellen

Comparing the Tonojet disposable tonometer with the traditional Goldmann tonometer in glaucomatous and non-glaucomatous eyes

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