Goldmann and error correcting tonometry prisms compared to intracameral pressure

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Abstract

Background

Compare Goldmann applanation tonometer (GAT) prism and correcting applanation tonometry surface (CATS) prism to intracameral intraocular pressure (IOP), in vivo and in vitro.

Methods

Pressure transducer intracameral IOP was measured on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically to 10, 20, and 40 mmHg. Simultaneously, IOP was measured using a Perkins tonometer with a standard GAT prism and a CATS prism at each of the intracameral pressures. Statistical comparison was made between true intracameral pressures and the two prism measurements. Differences between the two prism measurements were correlated to central corneal thickness (CCT) and corneal resistance factor (CRF). Human cadaver eyes were used to assess measurement repeatability.

Results

The CATS tonometer prism measured closer to true intracameral IOP than the GAT prism by 1.7+/−2.7 mmHg across all pressures and corneal properties. The difference in CATS and GAT measurements was greater in thin CCT corneas (2.7+/−1.9 mmHg) and low resistance (CRF) corneas (2.8+/−2.1 mmHg). The difference in prisms was negligible at high CCT and CRF values. No difference was seen in measurement repeatability between the two prisms.

Conclusion

A CATS prism in Goldmann tonometer armatures significantly improve the accuracy of IOP measurement compared to true intracameral pressure across a physiologic range of IOP values. The CATS prism is significantly more accurate compared to the GAT prism in thin and less rigid corneas. The in vivo intracameral study validates mathematical models and clinical findings in IOP measurement between the GAT and CATS prisms.

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Most cited references 15

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Central corneal thickness and corneal hysteresis associated with glaucoma damage.

Aimee Broman, Karen Bandeen-Roche, N Congdon … (2006)

We sought to measure the impact of central corneal thickness (CCT), a possible risk factor for glaucoma damage, and corneal hysteresis, a proposed measure of corneal resistance to deformation, on various indicators of glaucoma damage. Observational study. Adult patients of the Wilmer Glaucoma Service underwent measurement of hysteresis on the Reichert Ocular Response Analyzer and measurement of CCT by ultrasonic pachymetry. Two glaucoma specialists (H.A.Q., N.G.C.) reviewed the chart to determine highest known intraocular pressure (IOP), target IOP, diagnosis, years with glaucoma, cup-to-disk ratio (CDR), mean defect (MD), pattern standard deviation (PSD), glaucoma hemifield test (GHT), and presence or absence of visual field progression. Among 230 subjects, the mean age was 65 +/- 14 years, 127 (55%) were female, 161 (70%) were white, and 194 (85%) had a diagnosis of primary open-angle glaucoma (POAG) or suspected POAG. In multivariate generalized estimating equation models, lower corneal hysteresis value (P = .03), but not CCT, was associated with visual field progression. When axial length was included in the model, hysteresis was not a significant risk factor (P = .09). A thinner CCT (P = .02), but not hysteresis, was associated with a higher CDR at the most recent examination. Neither CCT nor hysteresis was associated with MD, PSD, or GHT "outside normal limits." Thinner CCT was associated with the state of glaucoma damage as indicated by CDR. Axial length and corneal hysteresis were associated with progressive field worsening.

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Effect of central corneal thickness, corneal curvature, and axial length on applanation tonometry.

Markus Kohlhaas, H-J Grein, Lutz Pillunat … (2006)

To evaluate the effect of central corneal thickness (CCT), corneal curvature, and axial length on applanation tonometry in an in vivo study. In a masked, prospective clinical trial, we examined 125 eyes of 125 patients scheduled for cataract surgery. Corneal curvature was measured by means of keratometry and axial length by A-scan ultrasonography. By cannulating the anterior chamber before surgery, intraocular pressure (IOP) was set to 20, 35, and 50 mm Hg in a closed system by means of a water column. After measuring thickness, the IOP was measured with an applanation tonometer. Pearson product moment correlations and multiple linear regression analyses were performed, and significance levels were evaluated by the paired, 2-tailed t test. The difference between measured and real IOP was significantly dependent (P < .001) on CCT. The associations between IOP and corneal curvature or IOP and axial length were not statistically significant (P = .31). The association between IOP reading and CCT is shown in the "Dresdner correction table," which illustrates an approximately 1-mm Hg correction for every 25-microm deviation from a CCT of 550 microm. The correction values were positive as thickness decreased and negative as thickness increased. Central corneal thickness significantly affects IOP readings obtained by applanation tonometry according to the Goldmann principle. A correction of IOP readings by considering CCT according to the Dresdner correction table might be helpful for determining an accurate IOP value.

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Why Do People (Still) Go Blind from Glaucoma?

Remo Susanna Junior, Carlos De Moraes, George A Cioffi … (2015)

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Author and article information

Contributors

Sean McCafferty: 520-327-3487 , sjmccafferty66@hotmail.com

Jason Levine: 520-327-3487 , jlevine46@comcast.net

Jim Schwiegerling: 520-621-8688 , jschwieg@u.arizona.com

Eniko T. Enikov: 520-621-4506 , enikov@email.arizona.edu

Journal

Journal ID (nlm-ta): BMC Ophthalmol

Journal ID (iso-abbrev): BMC Ophthalmol

Title: BMC Ophthalmology

Publisher: BioMed Central (London )

ISSN (Electronic): 1471-2415

Publication date (Electronic): 4 January 2018

Publication date PMC-release: 4 January 2018

Publication date Collection: 2018

Volume: 18

Electronic Location Identifier: 2

Affiliations

[1 ]ISNI 0000 0001 2168 186X, GRID grid.134563.6, Department of Ophthalmology, Intuor Technologies, , University of Arizona- College of Medicine, University of Arizona- College of Optical Science, ; LLC 6422 E. Speedway Blvd. Suite 100, Tucson, AZ 85710 USA

[2 ]ISNI 0000 0001 2168 186X, GRID grid.134563.6, Department of Ophthalmology, , University of Arizona- College of Medicine, ; 6422 E. Speedway Blvd. Suite 100, Tucson, AZ 85710 USA

[3 ]ISNI 0000 0001 2168 186X, GRID grid.134563.6, Department of Ophthalmology, , University of Arizona-College of Optical Science, University of Arizona-College of Medicine, ; 1630 E. University Blvd, Tucson, AZ 85719 USA

[4 ]ISNI 0000 0001 2168 186X, GRID grid.134563.6, Department of Aerospace and Mechanical, , University of Arizona-College of Engineering, ; 1130 N. Mountain Ave, Tucson, AZ 85721 USA

[5 ]Tucson, USA

Article

Publisher ID: 668

DOI: 10.1186/s12886-017-0668-z

PMC ID: 5753488

SO-VID: f2a487d5-bc81-448c-aa91-b57bb16e1339

License:

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

History

Date received : 29 April 2017

Date accepted : 13 December 2017

Funding

Funded by: FundRef http://dx.doi.org/10.13039/100000053, National Eye Institute;

Award ID: R43 EY026821-01

Custom metadata

ScienceOpen disciplines: Ophthalmology & Optometry

Keywords: glaucoma,intraocular pressure,iop,goldmann,bias,error,perkins,tonometer,applanation,cct,central corneal thickness,crf,corneal resistance factor,intracameral,cadaver eye,in vivo,in vitro,head position,upright,supine,manometric,corneal hydration

Data availability:

ScienceOpen disciplines: Ophthalmology & Optometry

Keywords: glaucoma, intraocular pressure, iop, goldmann, bias, error, perkins, tonometer, applanation, cct, central corneal thickness, crf, corneal resistance factor, intracameral, cadaver eye, in vivo, in vitro, head position, upright, supine, manometric, corneal hydration

Goldmann and error correcting tonometry prisms compared to intracameral pressure

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Abstract

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Results

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Karger: Ophthalmology

Most cited references 15

Central corneal thickness and corneal hysteresis associated with glaucoma damage.

Effect of central corneal thickness, corneal curvature, and axial length on applanation tonometry.

Why Do People (Still) Go Blind from Glaucoma?

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