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Tonometer Calibration: III. Volume of Indentation and P0 Determination

Tonometer Calibration: III. Volume of Indentation and P0 Determination Abstract The calibration of tonometers to give pressure in millimeters of mercury requires the determination of the pressure while the tonometer rests on the eye (Pt). With the Schiøtz tonometer Pt is considerably higher than the pressure in the undisturbed eye (Po) because the weight of the tonometer produces a large rise in pressure due to the fact that an appreciable quantity of fluid is displaced by the tonometer indentation (Vc). The relationship between the change in pressure from Po to Pt and the change in volume in the eye produced by the tonometer is determined by the rigidity of the ocular coats (E). If the pressure-volume relationship (rigidity) is known and Pt and Vc can be determined, it is then possible to calculate Po from the rigidity formula. In an earlier paper the results of making measurements of Pt on References 1. McBain, E. H.: Tonometer Calibration: Determination of Pt Formula by Use of Strain Gauge and Recording Potentiometer on Enucleated Normal Human Eyes , A.M.A. Arch. Ophth. 57:520, 1957.Crossref 2. Friedenwald, J. S.: Standardization of Tonometers: Decennial Report by the Committee on Standardization of Tonometers, American Academy of Ophthalmology and Otolaryngology, 1954. 3. Friedenwald, J. S.: Tonometer Calibration: An Attempt to Remove Discrepancies Found in the 1954 Calibration Scale for Schiøtz Tonometers , Tr. Am. Acad. Ophth. 61:108, 1957. 4. McBain, E. H.: Tonometer Calibration: II. Ocular Rigidity , A.M.A. Arch. Ophth. 60:1080, 1958.Crossref 5. Grant, W. M., and Trotter, R. R.: Tonographic Measurements in Enucleated Eyes , A.M.A. Arch. Ophth. 53:191, 1955.Crossref 6. Perkins, E. S., cited by Kronfeld, P. C.: The Present Status of the Calibration of Schiøtz Tonometers, to be published. 7. Prijot, E.: To be published. 8. Moses, R. A., and Becker, B.: Clinical Tonography: The Scleral Rigidity Correction , Am. J. Ophth. 45:196, 1958. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png A.M.A. Archives of Ophthalmology American Medical Association

Tonometer Calibration: III. Volume of Indentation and P0 Determination

A.M.A. Archives of Ophthalmology , Volume 63 (6) – Jun 1, 1960

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Publisher
American Medical Association
Copyright
Copyright © 1960 American Medical Association. All Rights Reserved.
ISSN
0096-6339
DOI
10.1001/archopht.1960.00950020938007
Publisher site
See Article on Publisher Site

Abstract

Abstract The calibration of tonometers to give pressure in millimeters of mercury requires the determination of the pressure while the tonometer rests on the eye (Pt). With the Schiøtz tonometer Pt is considerably higher than the pressure in the undisturbed eye (Po) because the weight of the tonometer produces a large rise in pressure due to the fact that an appreciable quantity of fluid is displaced by the tonometer indentation (Vc). The relationship between the change in pressure from Po to Pt and the change in volume in the eye produced by the tonometer is determined by the rigidity of the ocular coats (E). If the pressure-volume relationship (rigidity) is known and Pt and Vc can be determined, it is then possible to calculate Po from the rigidity formula. In an earlier paper the results of making measurements of Pt on References 1. McBain, E. H.: Tonometer Calibration: Determination of Pt Formula by Use of Strain Gauge and Recording Potentiometer on Enucleated Normal Human Eyes , A.M.A. Arch. Ophth. 57:520, 1957.Crossref 2. Friedenwald, J. S.: Standardization of Tonometers: Decennial Report by the Committee on Standardization of Tonometers, American Academy of Ophthalmology and Otolaryngology, 1954. 3. Friedenwald, J. S.: Tonometer Calibration: An Attempt to Remove Discrepancies Found in the 1954 Calibration Scale for Schiøtz Tonometers , Tr. Am. Acad. Ophth. 61:108, 1957. 4. McBain, E. H.: Tonometer Calibration: II. Ocular Rigidity , A.M.A. Arch. Ophth. 60:1080, 1958.Crossref 5. Grant, W. M., and Trotter, R. R.: Tonographic Measurements in Enucleated Eyes , A.M.A. Arch. Ophth. 53:191, 1955.Crossref 6. Perkins, E. S., cited by Kronfeld, P. C.: The Present Status of the Calibration of Schiøtz Tonometers, to be published. 7. Prijot, E.: To be published. 8. Moses, R. A., and Becker, B.: Clinical Tonography: The Scleral Rigidity Correction , Am. J. Ophth. 45:196, 1958.

Journal

A.M.A. Archives of OphthalmologyAmerican Medical Association

Published: Jun 1, 1960

References

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