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November 1964

Comparability of a Sample of Certified Schiotz Tonometers: With an Evaluation of the Potential Influence of Tonometer Variability on the Outcome of Epidemiologic Field Studies

Author Affiliations

Bethesda, Md
Head, Ophthalmology Projects, Epidemiology Branch (Dr. Schwartz); Statistician, Biometrics Branch (Mr. Ambler).; From the National Institute of Neurological Diseases and Blindness.

Arch Ophthalmol. 1964;72(5):672-678. doi:10.1001/archopht.1964.00970020672018

Introduction  Any attempt to determine the prevalence of glaucoma with sufficient accuracy to permit legitimate geographic comparisons will require carefully standardized instruments and procedures. For such epidemiologic field studies the use of tonometers of established precision is a preliminary and fundamental requirement.Inconsistency among the recordings obtained from various Schiotz indentation tonometers has led to attempts to establish acceptable manufacturing tolerance. Largely through the extensive efforts of the Committee on Standardization of Tonometers of the American Academy of Ophthalmology and Otolaryngology, there has been considerable improvement in the uniformity of available instruments. Still, it is suggested that residual inconsistencies may exist in theory1 and in fact.2-4Since the Epidemiology Branch of the National Institute of Neurological Diseases and Blindness proposes quantitative field investigations of the relative frequency of chronic simple glaucoma among selected populations, an examination of the comparability among a sample of Schiotz tonometers was undertaken. The

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